Pilot Study of Time Restricted Feeding as a Weight Loss Intervention in Overweight and Obese Adults
Phase: NA
Conditions: Obesity
Sponsor: University of Colorado, Denver

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Title: Pilot Study of Time Restricted Feeding as a Weight Loss Intervention 
NCT03571048 
Last updated: 10/14/2020 

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COMIRB Protocol 
COLORADO MULTIPLE INSTITUTIONAL REVIEW BOARD 
CAMPUS BOX F-490    TELEPHONE:  303-724-1055  Fax:  303-724-0990 
 
 
 
Protocol #: 18-0487 
Project Title: Pilot study of time restricted feeding as a weight loss intervention in 
overweight and obese adults  
 
 
 
Principal Investigator:  Elizabeth Thomas, MD 
Version Date: 10/14/2020 
 
 
 
 
 
  
 
I. Hypotheses and Specific Aims:   
 
The circadian timing of energy intake (EI) has emerged as a key factor in the regulation of body 
weight1,2. Studies have suggested that eating meals later in the evening or during the biological 
night when the circadian system is promoting sleep adversely influences the success of weight loss 
therapy2-7. In contrast, restricting EI to a short window during waking hours and extending the 
length of the overnight fast (i.e., time restricted feeding, TRF) may be a practical and useful 
strategy for promoting weight loss and weight maintenance1,8,9. However, potential benefits of 
adding TRF to a weight loss program have yet to be evaluated in a well-controlled clinical study. 
The overall objective of this proposal is to provide a foundation to inform the design of a future 
large-scale trial to evaluate the efficacy of TRF in generating weight loss. Our overall hypothesis is 
that feasibility, adherence, and acceptability of a weight loss intervention using TRF in the setting of 
a reduced calorie diet (RCD) – RCD+TRF - will be similar to compliance with an intervention using 
a reduced calorie diet alone (RCD), suggesting acceptability for a future large-scale trial. In this 12-
week pilot and feasibility study, 60 overweight and obese individuals will be randomized 1:1 to 
RCD+TRF (EI restricted to a 10-hour window starting 1 hour from habitual waking time) or standard 
RCD (no restriction on feeding duration). The total duration of the intervention is 9 months. 
Measures include feasibility, acceptability and adherence to the interventions, body weight, body 
composition (DXA), EI (smart phone application), physical activity (PA, accelerometery), glucose 
variability (continuous glucose monitoring, CGM), sleep (questionnaires and polysomnography), 
and nocturnal substrate metabolism (room calorimetry). The specific aims (SA) are: 
Specific Aim 1a.  To evaluate the feasibility and acceptability of a 9-month TRF 
intervention compared to a standard dietary weight loss intervention (i.e. RCD). Feasibility of 
enrollment and retention, and acceptability of the intervention will be assessed in adults with 
obesity meeting inclusion/exclusion criteria proposed for the future large-scale trial. We will assess 
adherence to the weight loss programs, as measured objectively with a novel smartphone 
application and verified with CGM data, and subjectively with the use of questionnaires. We expect 
adherence to the RCD+TRF intervention will be similar to the RCD group, suggesting acceptability 
for a future large-scale trial. If we find differences in adherence between programs, the data will be 
used to optimize the RCD+TRF program prior to the future large-scale trial. 
Specific Aim 1b. To assess the efficacy of RCD+TRF compared to RCD alone in producing 
weight loss at 12 weeks and reducing the risk of weight regain after 6 months of follow-up. 
Although the number of subjects included in this pilot study does not provide sufficient statistical 
power to detect differences in weight loss between groups, the data obtained will provide estimates 
of variability and effect size to assist with power and sample size calculations for the future large-
scale trial. 
Exploratory Aim.  To explore potential mechanisms contributing to any observed 
differences between groups we will evaluate (A) objective measures of free-living behavior 
(energy intake, physical activity, and sedentary behavior) and (B) objective measures of 
glucose variability, sleep and energy metabolism Preliminary data on free-living behaviors and 

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in-laboratory measures of sleep and energy metabolism will allow us to further optimize a future 
trial and probe mechanisms to explain any weight loss differences between groups.  
 
II. Background and Significance:  
 
The question of whether when we eat is as important as how much remains unanswered 
and is critical in the development of future recommendations regarding body weight 
regulation. Altering meal frequency has been evaluated as a weight loss strategy due to 
epidemiological studies showing an inverse relationship between meal frequency and adiposity10,11, 
but interventional studies have shown conflicting results, with no definitive evidence of differences 
in weight loss or metabolic risk factors12-15. Breakfast eating is also recommended due to evidence 
linking breakfast skipping with obesity16-20. However, several interventional studies have failed to 
show weight loss with breakfast eating21-23. On the other hand, in two weight-loss interventions, 
individuals who consumed more calories in the morning as compared to the evening lost more 
weight, even though both EI and self-reported PA were similar2,3. In addition, food intake at night 
(as seen with shift work), is linked to obesity independent of EI24.  
There are physiologically plausible mechanisms by which restricting EI to a window aligned 
with the early part of the day (i.e. TRF) may enhance weight loss and result in more favorable 
metabolic outcomes. A number of metabolic systems are entrained to circadian rhythms, including 
hormone, lipid and glucose concentrations, intestinal lipid absorption, and autonomic nervous 
system activity25. Restriction of EI to a window of time and/or extension of the fasting period may 
alter diurnal patterns and circadian rhythms in glucose and lipid metabolism in a manner that favors 
decreased obesity risk. In rodent studies, metabolic benefits were seen with a TRF protocol, 
despite equivalent EI of a high fat diet8,9.  Only two studies of TRF have been done in humans. Gill 
and Panda26 studied 8 overweight men and women with habitual eating duration >14 hours who 
were asked to restrict EI to a self-selected 10-11 hour window. Subjects lost weight (-3.27 kg), 
despite the fact that they were not specifically told to decrease their EI. Similarly, LeCheminant et 
al27 studied 29 healthy young men in a cross-over design with a period of night eating restriction 
(no EI from 1900 to 0600 hrs) vs control, without recommendation to decrease EI, and found a 
modest weight reduction after 2 weeks (-0.4 kg). However, these studies were small and not 
designed as weight loss interventions.  
This pilot study proposal is highly significant because we plan to address the gap in knowledge 
regarding the effects of EI timing on weight loss, which was recently highlighted as a priority 
research area by the NIH28. Results may have substantial influence on evidence-based weight-
management recommendations and guidelines. While caloric restriction is a necessary component 
of all weight loss regimens29, most individuals struggle to adhere to a reduced calorie diet long-
term30,31. Studies of different weight loss diets show significant variability in weight loss success30, 
and patients may need to try multiple different strategies before finding one that is successful and 
sustainable. In the era of individualized medicine, the ability to choose the most suitable dietary 
strategy for an individual patient would increase the likelihood of successful weight loss.  
Innovation: We believe there are 4 innovative aspects to the proposed studies. First, TRF has 
yet to be evaluated as a weight loss strategy. The ultimate goal of assessing dietary patterns is 
to identify those patterns which may be able to effectively produce weight loss, so a clinical study 
assessing weight loss outcomes is critical to determining the relevance of this line of research. 
While many studies have evaluated weight loss interventions with variations on number of meals 
and/or macronutrient content of the diet, studies evaluating the timing of food intake are notably 
lacking. Second, TRF has not been evaluated within the context of a behavioral weight loss 
intervention that includes a moderately reduced calorie diet and behavioral support to 
facilitate adherence32. Provision of a comprehensive program will likely enhance adherence to 
TRF and result in greater weight loss. Developing a TRF behavioral support curriculum is 
innovative and will inform the delivery of the intervention during the larger trial. Third, the project 
seeks to develop a number of novel approaches to study the effects of TRF on free-living 
behaviors. For example, we propose the use of a smartphone application with photographic food 

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records in combination with continuous glucose monitoring (CGM) to capture free-living EI and 
monitor adherence to the program. In addition, we will evaluate the effects of TRF on free-living PA 
and sleep. In the Bath Breakfast Project, individuals were found to have greater physical activity 
energy expenditure when consuming as compared to skipping breakfast21,23. Also, sleep restriction 
alters food intake and habitual physical activity33, but less is known about how dietary patterns 
affect sleep. Food intake near the onset of sleep is negatively associated with sleep quality,4-6 so it 
may be hypothesized that the early TRF paradigm could improve sleep. Finally, we will measure 
sleep and nocturnal energy metabolism in a subset of subjects (n=5) in each group (RCD 
and RCD+TRF) following the intervention and correlate these measures with longitudinally 
determined weight regain at 6 months. These studies will allow us to start collecting data on 
physiological processes that might promote weight regain or support weight maintenance following 
weight loss. TRF studies in rodents show favorable adaptive responses to nocturnal nutrient 
oxidation that appear to be protective against metabolic challenges such as high fat feeding8,9,26. If 
these adaptive responses in nocturnal nutrient metabolism observed in rodents translate to 
humans, then TRF may be a potent strategy for promoting weight maintenance in reduced obesity, 
the most vexing problem facing obesity treatment. 
 
III. Preliminary Studies/Progress Report:   
 
The idea to study TRF comes from our group’s experience with breakfast skipping studies22,34. 
While our study22, as well as other interventional trials21,23 failed to show weight loss with breakfast 
skipping, these studies did not evaluate the timing of food intake throughout the rest of the day. In 
contrast, we34 and others35 have shown that breakfast skipping was acutely associated with an 
increased insulin response to lunch, and other studies have shown increased glucose variability21 
and insulin resistance23 with breakfast skipping. This, along with emerging research relating to the 
meal timing and the circadian regulation of metabolic systems36, provides a physiological basis for 
potential metabolic benefits of TRF.  
 
IV. Research Methods 
 
A.  Outcome Measure(s):   
 
Primary Outcomes: 
• 
Feasibility and tolerability of the interventions assessed by enrollment and retention 
numbers, protocol related adverse events (AE’s), and questionnaires assessing 
satisfaction, quality of life and mood. 
• 
Adherence to interventions assessed both with self-report and with the use of a 
smartphone application in conjunction with continuous glucose monitoring. 
 
Secondary Outcomes: 
• 
Weight (scale) and body composition (DXA) obtained at baseline (prior to the weight 
loss intervention), at 12 weeks (following the weight loss intervention), and at a 6mo 
follow-up time point.  
• 
Physical activity assessed by accelerometry 
• 
Free-living sleep patterns assessed by wrist actigraphy 
• 
Objective (in-laboratory) sleep recording using Compumedics Inc Siesta digital sleep 
recorders 
• 
Meal timing and energy intake assessed by photographic food records 
• 
Patterns in 24h glucose assessed by continuous glucose monitors over 7 days before 
and after the weight loss intervention 
• 
Questionnaire based measures of appetite 
• 
HgbA1c and lipids  
• 
Resting metabolic rate and nocturnal energy metabolism by indirect calorimetery 
 
B. Description of Population to be Enrolled:   

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Inclusion criteria.  
• 
Adult males and females with a BMI of 27-45 kg/m2 and weight stable over the previous 6 
months; 
• 
Age, 18-50 years old; 
• 
Passing medical and physical screening, and analysis of blood and urine screening 
samples; 
• 
Typical eating duration >12 hours per day (assessed by questionnaires); 
• 
Own a smartphone 
• 
Reside or work within approximately 30 minutes driving distance of CU-AMC (potential 
participants living outside of this driving distance could be included in the study at the PIs 
discretion).  
• 
For participants in the optional Reproductive Hormone Sub-study: females, age 18-40, with 
regular menstrual cycles (between 18-40 days). 
Exclusion criteria.  
• 
Pregnancy or lactation for women (women who are >6 months postpartum with no plans of 
becoming pregnant in the next year and who are not currently lactating can be included; 
oral contraceptives will be allowed if medication has been consistent for the prior 6 months) 
• 
Postmenopausal women (menopausal status will be assessed during the history and 
physical, with requirement of self-reported regular menstrual cycles for the last year; 
women who have undergone hysterectomy but with ovaries in place who continue to have 
regular menstrual symptoms can be included) 
• 
Being considered unsafe to participate as determined by the study physician; 
• 
History of cardiovascular disease, diabetes, uncontrolled hypertension, untreated thyroid, 
renal, hepatic diseases, dyslipidemia or any other medical condition affecting weight or 
lipid metabolism; 
• 
History of human immunodeficiency virus or hepatitis B or C (self-report); 
• 
Taking medications affecting weight or energy intake/energy expenditure in the last 6 
months, including weight loss medications, antipsychotic drugs or other medications as 
determined by the study physician; 
• 
Having abnormal blood chemistry (eGFR<45mL/min, AST or ALT >3 times the upper limit 
of normal)  or as deemed significant by the study physician; 
• 
Being a smoker or having been a smoker in the 3 months prior to their screening visit; 
• 
Working night shifts; 
• 
For participants completing the PSG studies, extreme early or extreme late chronotype as 
determined by the Munich Chronotype questionnaire37. Participants completing the primary 
weight loss intervention will not be excluded based on chronotype; 
• 
Night eating syndrome (at least 25% of food intake is consumed after the evening meal 
and/or at least two episodes of nocturnal eating per week) as assessed with meal pattern 
assessment questionnaire; 
• 
For participants completing the PSG studies, greater than moderate sleep apnea (score 
high risk ≥ 2 or more categories on the Berlin Questionnaire). Participants completing the 
primary weight loss intervention will not be excluded based on Berlin OSA risk scores. 
• 
For participants completing the PSG studies, use of medications affecting sleep 
(benzodiazepines and other sleep aids, as determined by study physician). Participants 

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completing the primary weight loss intervention will not be excluded based on use of 
medications affecting sleep. 
• 
Binge eating behaviors as identified by a score of >17 on the Binge Eating Scale (BES)38. 
• 
For participants in the optional Reproductive Hormone Sub-study: Current use of hormonal 
contraceptives, or use of hormonal contraceptives during the 4 months prior to the start of 
the weight loss intervention, previous diagnosis of polycystic ovarian syndrome.   
 
 
C. Study Design and Research Methods   
 
Informed consent, medical screening, labs, questionnaires, and baseline metabolic rate 
assessment. 
Informed consent, medical evaluation and labs. After telephone screening, interested participants 
will be scheduled for an in-person screening visit to determine eligibility. After providing written 
informed consent, participants will undergo the following evaluations: medical history and physical 
examination (including measurement of weight, height, BP, HR), and screening tests (Hemoglobin 
A1C, lipid panel, comprehensive metabolic panel, TSH and pregnancy test). Patients who have 
had these tests done and found to be normal within the last 6 months may submit the results and 
forego the screening labs. If any screening test is abnormal the participant will be informed 
immediately and asked to follow-up with his/her doctor. 
Questionnaires. Participants will be asked to complete a meal pattern assessment questionnaire to 
assess for components of night eating syndrome, as well as the Munich Chronotype 
Questionnaire37 to evaluate chronotype. In addition, participants will complete the Binge Eating 
Scale (BES), a 16-item survey used to identify the presence and severity of binge eating 
behaviors38. 
Resting energy expenditure (REE):  REE will be measured after an overnight fast using standard 
indirect calorimetry39 (Parvo Medics TrueOne 2400, Salt Lake City, UT). 
 
To enhance feasibility of recruitment, participants can complete the informed consent and history 
and physical exam during a separate visit from the screening/baseline procedures that require 
fasting (blood draw and REE measurement). In addition, participants may undergo DXA testing at 
the screening visit if screening is done within 4 weeks of the intervention start date. 
 
Baseline Assessments (7-day period no less than 4 weeks prior to starting the weight loss 
intervention). 
EI and meal timing will be measured using photographic food records by utilizing the camera 
function of participants’ smartphones to take a picture of the food or beverage. Participants will be 
provided with detailed instructions regarding methods of taking food photographs, as outlined by 
the CTRC Nutrition Core. After taking the photographs, participants will text photographs directly to 
either a Meallogger account or a Google Voice account (note: an amendment was submitted in 
1/2020 to switch to Google Voice after data collection using Meallogger in Cohorts 1 and 2 were 
already completed.). Subjects will be asked to record every intake event for 7 continuous days. The 
data from this 7-day recording period will be used to assess timing of energy intake in both groups, 
and adherence to time restriction in those patients in the RCD+TRF group. In addition, this 
information will be compared with data from continuous glucose monitoring to determine whether 
glucose excursions exist in the absence of recorded food intake events. Based on published data40 
showing that mean post-prandial glucose excursions in patients with normal glucose tolerance are 
~40.5 mg/dL, this threshold will be used to indicate an episode of food intake.  EI will be estimated 
using the food images collected during the last 3 days of the 7 day recording period by staff in the 
CTRC Nutrition Core, as previously described41,42. 
 
Glucose variability: Free-living plasma glucose levels will be measured with a glucose monitoring 

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system (FreeStyle LibrePro, Chicago, IL) for 7 continuous days coinciding with the cell phone-
based meal tracking described above. The device consists of a sensor applied to the back of the 
patient's upper arm that measures glucose in interstitial fluid every 15 minutes.  
 
Patterns of PA and Sedentary Behavior:  The activPAL3 micro (PALTechnologies, Glasgow, 
Scotland) will be used to estimate time spent in moderate-to-vigorous PA (MVPA), light activity, 
and sedentary behavior over a 7-day period at baseline. The activPAL3 micro uses accelerometer-
derived information about thigh position to estimate time spent in different body positions. The time-
stamped “event” data file from the activPAL software will be used to determine time spent sitting, 
standing, and stepping per day.  
 
Appetite will be measured using visual analog scales (VAS) before and after each meal for the final 
3 days of cell phone meal tracking as previously described43 and as used by our group in prior 
studies34,44,45. 
 
Free-living Sleep Patterns: Subjects will complete several validated questionnaires to evaluate 
aspects of daytime sleepiness, sleep quantity/quality, and sleep timing: Berlin Questionnaire, 
Epworth Sleepiness Scale46, Pittsburgh Sleep Quality Index47, and Morningness -Eveningness 
Questionnaire48. Each subject will also keep a written log of sleep/wake times and wear a wrist 
activity and light exposure recorder to document free-living sleep/wake patterns for 7 continuous 
days (Actiwatch Spectrum, Philips Respironics, Bend, OR). 
 
Mood, quality of life and eating behaviors: Quality of life (QOL) will be assessed with the RAND-
3649,50 physical and mental health component summary score. Mood state will be assessed with 
the Profile of Mood States 40 Item Questionnaire (POMS-40)51-53. Eating behaviors will be 
assessed with the Three Factor Eating Questionnaire (TFEQ)54.   
 
Body Weight and Composition Assessment. Body weight and composition will be measured using 
a digital scale and dual energy x-ray absorptiometry (DXA, Hologic Inc., Bedford, MA). 
Resting energy expenditure (REE):  the resting metabolic rate measurement would be repeated in 
any participant presents with significant weight gain or loss (+/-2kg) between the time screening 
and the time of baseline assessments. Otherwise, the REE measurement performed at the time of 
screening will be considered as the baseline. 
Optional In-laboratory assessments: 
 
Nocturnal energy metabolism: Participants will be invited to spend a night in the UCH whole room 
calorimeter for the measurement of nocturnal energy metabolism. We aim to perform 
approximately n=5 room calorimeter studies per group depending on budget. To facilitate 
recruitment for the optional procedure, the evening spent in the room calorimeter could be 
completed any night following study enrollment and prior to starting the weight loss intervention 
(except for during the 7-day free-living assessment of meal timing, EI, and activity described 
above). Prior to the room calorimeter stay, participants will be asked to perform 3-days of sleep 
logs and cell phone based meal logging with time stamps to ensure meal and sleep timing are 
consistent prior to the chamber stay. Subjects will be provided an energy balance diet (calculated 
as RMR times an individually determined activity factor) on the day of the overnight chamber stay 
at baseline. The macronutrient composition of the diet will be the same at baseline and at the 12-
week follow-up: carbohydrate = 50%, fat = 35%, and protein = 15% (percent daily caloric 
intake:25% breakfast, 30% lunch, 35% dinner, and 10% afternoon snack). The meals will be eaten 
over a 12 hour period as follows: subjects will be asked, “when can you eat your first meal in the 
morning? (1, 2, or 3 hours after waking?)”. This clock time will be T0. The meal times are then set 
at +5 (lunch) , +8 (snack). +11.5 (dinner) after T0. . Subjects will arrive at the CTRC at least 2 
hours before dinner and be placed in the room calorimeter at  their habitual bedtime for 
measurement of nutrient oxidation and energy expenditure as previously described55.  Substrate 
oxidation will be calculated from urine nitrogen excretion, O2 consumption and RQ based on 
published equations56. The chamber stay will be repeated at the 12-week follow up (between 

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weeks 12 and 16). The energy content of the diet will be determined based on RMR measured at 
baseline and reduced by 10% (as per weight loss intervention dietary prescription). In addition, 
participants in the TRF group will be asked to eat all food within their chosen 10-hour eating 
window as follows: where their habitual breakfast time is T0, Lunch=+4h, snack=+6h, and 
dinner=+9.). Participants in the RCD group will eat all meals within the same 12-hour eating 
window as was followed at baseline. The rationale for measuring nocturnal metabolism is that 
previous studies (including recent studies from our group) show that nocturnal energy expenditure 
and fat oxidation are independent predictors of longitudinal weight change. It is likely that the 
RCD+TRF and the standard RCD interventions will have differential effects of nocturnal fuel 
partitioning which could predict rates of weight regain in the groups. 
 
Polysomnographic (PSG) sleep recording and scoring. During the night spent in the room 
calorimeter subjects will be fitted with Compumedics Inc Siesta digital sleep recorders. The PSG 
study will consist of an electrocardiogram (ECG) and electroencephalogram (EEG), 
electromyogram (EMG), electrooculogram (EOG), and respiratory bands placed over the chest and 
abdomen. The sleep study will be scored according to revised AASM guidelines. Sleep latencies 
will be defined as follows: sleep onset latency (SOL), time from lights out to the onset of three 
continuous epochs of PSG-defined sleep; latency to persistent sleep (LPS), time from lights out to 
the onset of 10 continuous minutes of PSG-defined sleep; latency to slow wave sleep (SWSL), time 
from LPS to SWS; and REM sleep latency (REML), time from LPS to REM sleep. Sleep stages 
(stage 1 sleep, stage 2 sleep, SWS, and REM) will be matched with EE values offset by 2 min to 
account for the lag-time response of the whole-room calorimeter relative to the timing of the sleep 
recording. 
 
Behavioral Weight Loss Program (Weeks 1-39).   
Following completion of the baseline assessments, all participants will receive a 9-month group-
based behavioral weight loss program, with randomized groups meeting separately. Participants 
will be randomized 1:1 to RCD+TRF or RCD. Groups will be held at the AHWC and will be taught 
by an RD with experience in leading group-based behavioral weight loss interventions. In case of 
situations in which in-person classes cannot be held (i.e., due to concern for transmission of 
disease during the COVID-19 global pandemic), meetings will be held virtually via Zoom. Zoom is a 
HIPAA compliant web and video conferencing platform. All participants will be provided with a link 
to join the meeting and instructions regarding optimal conditions in which to join the meeting (i.e., a 
quiet location with minimal distractions and ability to devote full attention to the meeting). Group 
meetings will be moved back to in-person when it is deemed safe to do so.  Group meetings will 
take place weekly during weeks 1-12, then monthly between months 4 and 9. Groups will meet 
separately to maintain intervention integrity. Classes will last ~60 minutes and the curriculum will 
be delivered using a mix of large group discussion, small breakout discussions, visual 
demonstrations, and written exercises. The programs will fulfill all recommendations for behavioral 
interventions outlined in current guidelines32. Current guidelines suggest the most effective 
behavioral treatment for obesity is a high-intensity, comprehensive weight loss intervention 
provided in individual or group sessions by a trained interventionist with principle components of a 
moderately reduced calorie diet, increased PA, and behavioral support to facilitate adherence 32. 
Curriculum will be based on the Colorado Weigh behavioral weight loss program, which uses a 
skills-based approach and cognitive behavioral strategies for lifestyle modification with a dietary 
focus on daily caloric restriction57,58. The Colorado Weigh curriculum includes topics addressing the 
importance of exercise for weight loss. Specifically, the recommendations are for participants to 
achieve 150 min/wk of exercise, but exercise will not be supervised. Curriculum for RCD+TRF will 
be developed by Dr. Thomas, with input from a registered dietitian and will feature similar weekly 
themes as RCD, but modified to focus on support specific to TRF. 
 
Dietary and Activity Prescriptions. Both groups will focus on caloric restriction to decrease overall 
EI. Participants will be given a personalized calorie goal based on their measured RMR. If RMR by 
indirect calorimetry and by Mifflin St-Jeor equation differ by >10%, then the average of the 2 values 
will be used. This estimated RMR will be reduced by 10% and then rounded to the nearest 100 kcal 

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Suggested macronutrient content (55% carbohydrates, 15% protein, 30% fat) will be the same for 
both groups. Participants in the RCD group will not be given any specific instruction regarding 
timing of food intake. Participants in the RCD+TRF group will be instructed to eat only during a 
window of 10 hours, starting within 3 hours of waking. They will also be instructed in specific 
strategies to support TRF including:  strategies to deal with hunger outside eating windows, 
distraction techniques, and choosing a balanced diet/appropriate portions during feeding windows. 
All participants will be counseled on the importance of PA for weight loss and will receive a 
recommendation to perform 150 min/wk of PA.  
 
Self-Reported Dietary Adherence, Effort, and Self-Efficacy:  At weeks 4, 8 and 12, participants will 
be asked to rate on a 1-10 Likert scale: 1) how adherent they were to prescribed study diet over the 
past week, 2) how hard was it to adhere to prescribed study diet over the past week, and 3) how 
likely they feel they can adhere to prescribed diet for the next month30. These questionnaires will 
also be administered monthly from month 4 through 9 to determine whether participants have 
continued to follow their prescribed dietary pattern. In addition, participants will be asked to use the 
Meal Logger app (Cohorts 1 and 2) or Google Voice at weeks 4 and 8, and monthly between 
months 4 and 9 in order to objectively assess adherence to the dietary intervention. 
 
Intervention Safety and Tolerability: Participants will be asked to report AEs to study staff as they 
occur, to be reported to our IRB as per institutional guidelines. We will collect additional parameters 
to assess tolerability at week 12 and at the 6 month follow up visit. Quality of life (QOL) will be 
assessed with the RAND-3649,50 physical and mental health component summary score. Mood 
state will be assessed with the Profile of Mood States 2 (POMS-2)51-53. Eating behaviors will be 
assessed with the Three Factor Eating Questionnaire (TFEQ)54.   
 
Intervention Acceptability: Satisfaction with both the standard RCD and RCD+TRF program 
intervention will be assessed at week 12 and month 9 with a questionnaire that asks participants to 
rate on a 1-10 Likert scale how satisfied they were with specific domains of the intervention. The 
major domains that will be assessed are satisfaction with: 1) ability to adhere to caloric restriction 
and time restriction (for RCD+TRF group), 2) content of the dietary support curriculum, 3) content 
of the exercise support curriculum, 4) group meeting frequency and structure, and 5) weight loss 
achieved to date. Participants will also be asked in open-ended fashion to provide feedback on 
each domain of the intervention. We will also assess intervention acceptability by comparing the 
frequency of protocol related AE’s, requirement for protocol modification, and attrition between 
groups. 
In addition, at the end of the intervention, participants in both the TRF and RCD groups (n=6-8 per 
group) will be asked to participate in focus groups led by Dr. Masters, a licensed clinical health 
psychologist with experience developing heath focused behavioral interventions and conducting 
focus group research. The participants will be required to fill out an additional consent form. If the 
study team is unable to meet with them in person to obtain consent, then a virtual consent will take 
place via ZOOM. The goal of the focus groups will be to obtain more specific information about 
their perceptions of, and experiences with, the intervention. Participants will specifically be asked to 
discuss, via open-ended inquiry and discussion: 1) aspects of the intervention itself that were 
difficult or relatively easy to follow; 2) barriers that limited their adherence or satisfaction; 3) 
beneficial aspects of the intervention; 4) factors that facilitated their ability to adhere to the 
intervention; 5) aspects that they would change and their recommended changes. To obtain a more 
complete understanding of the participants’ experiences, extensive efforts will be made to include 
individuals who were non-adherent or dropped out of the interventions. A research assistant will 
attend the focus groups to act as a scribe, and the sessions will also be recorded using an audio 
recording device which will be later used to transcribe the entire session. Once the recording has 
been transcribed, the audio recording will be deleted. Data in response to the open-ended queries 
will be analyzed by the focus group leader using primarily inductive procedures, searching for 
themes that could inform intervention refinement in advance of a larger clinical trial. The focus 
groups will last 60-90 minutes and will be conducted at the Anschutz Health and Wellness Center. 

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In case of situations in which in-person classes cannot be held (i.e., due to concern for 
transmission of disease during the COVID-19 global pandemic), meetings will be held virtually via 
Zoom. Zoom is a HIPAA compliant web and video conferencing platform. All participants will be 
provided with a link to join the meeting and instructions regarding optimal conditions in which to join 
the meeting (i.e., a quiet location with minimal distractions and ability to devote full attention to the 
meeting).  
 
Adherence: Adherence to the prescribed study diet will be objectively assessed through review of 
meal logs collected with the MealLogger app and Google Voice account as described above, as 
well as through evaluation of glucose excursions in comparison with the meal logs in order to 
determine if glucose excursions exist in absence of recorded food intake. In addition, adherence 
will be assessed subjectively as described above through the use of questionnaires using Likert 
scales to address ability to adhere to the study diet. 
 
Post-intervention assessments. Within 3 weeks following the initial 12-week weight loss 
intervention all participants will complete 7 days of free-living EI recording (cell phone app), PA 
recording (accelerometers), sleep recording (wrist actigraph), appetite recording (VAS), and 
glucose monitoring (CGM) as described above for the baseline assessments. Participants will also 
have repeat assessments of HgbA1c, lipid panel, resting metabolic rate and body composition 
(DXA) during an outpatient CTRC visit. Participants will also repeat questionnaires as described 
above: adherence to the dietary intervention, QOL (RAND-36), mood state (POMS-2), eating 
behaviors (TFEQ), and sleep questionnaires (Berlin Questionnaire, Epworth Sleepiness Scale, 
Pittsburgh Sleep Quality Index, and Morningness -Eveningness Questionnaire). Participants 
completing the optional in-laboratory room calorimeter and objective sleep measurements at 
baseline will be asked to complete follow-up measurements. The follow-up measurements of sleep 
and nocturnal energy metabolism can be completed on any evening starting at week 10 of the 
intervention not to exceed 4 weeks following completion of the intervention. The only exception is 
that the inpatient visit cannot occur during the 7 days of free-living EI, PA, and glucose monitoring.  
 
COVID-19 Post Intervention Changes  
 
Due to the COVID-19 pandemic, we are unable to carry out week 12 measures as described 
above. Instead, the study team will drop off the accelerometer and wrist actigraph to participant’s 
homes. The packet of devices will be left on the participant’s doorstep to eliminate person to 
person contact. Proper PPE will be worn by the study team during the drop-off and pick-up time 
including gloves and masks. The participants will be asked to wait a few days before wearing the 
devices and encouraged to wipe each device down before placing it back in the packet for pick-up. 
Once the participants have worn the device for 7 consecutive days, the study team will pick up the 
devices from the doorstep and wipe down the packet with a disinfecting wipe. The devices will not 
be handled by the study team for at least 1 week post pick-up. The devices will be handled as 
follows:  
 
- The study team will wear gloves and a mask any time they are handling devices 
- Devices will be disinfected with a Cavi-wipe before being placed in the individual device packets 
- Each device will be placed in its own sanitized plastic bag before being placed in the device 
packet 
- Devices will be given to the entire cohort on one date, so that there will be no sharing of devices 
between participants  
- No study team member will handle devices if they are exhibiting symptoms of COVID-19 or have 
been exposed in the last 14 days.  
 
These measures will be put into place so long as the orders from campus, local, state, or federal 
government are such that the study measures cannot be carried out as originally planned. The 
study team will resume normal visit procedures once it is safe and permitted to do so.  
 

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We will still collect all non-contact outcomes such as the appetite recording (VAS), and the 7 days 
of food logging via Google voice. In addition to these measures, for the cohort participating in the 
weight loss intervention during the COVID-19 pandemic only, we will administer a questionnaire 
specific to COVID-19 (changes in work, levels of motivation, ability to adhere to the diet, etc) as 
well as the Perceived Stress Scale, a validated psychological instrument for measuring the 
perception of stress. CTRC measures such as the DXA, blood panel, and resting metabolic rate will 
not be collected under these circumstances.  
 
 
6-month follow-up assessments. Participants will continue to attend monthly group meetings 
during months 4-9. At 6-months following the completion of the weight loss intervention all subjects 
will be asked to come into the CTRC for repeat measures of RMR, body weight (scale) and 
composition (DXA). In addition, they will be asked to repeat questionnaires assessing adherence to 
the dietary intervention, satisfaction with the intervention, QOL (RAND-36), mood state (POMS-2), 
eating behaviors (TFEQ), and sleep (Berlin Questionnaire, Epworth Sleepiness Scale, Pittsburgh 
Sleep Quality Index, and Morningness -Eveningness Questionnaire, and Munich Chronotype 
Questionnaire). Due to the switch we made to ZOOM classes mid-intervention, we will send out a 
survey to the participants that asks about their experience with the online platform and how it 
compared to their in-person classes. We have also amended the focus group questions to ask 
about this as well.  
 
Optional Reproductive Hormone Sub-study Procedures: Urine Collection to Evaluate 
Reproductive Hormones. These measures serve as markers of hypothalamic-pituitary-ovarian 
(HPO) axis function, which is evidenced to be suppressed in both women with obesity, as well as 
women with low energy availability (i.e., restricting energy intake or exercising intensely), which is 
the cornerstone of behavioral obesity treatment. Funding for these measures is provided by an NIH 
K award (HL 143039; PI Caldwell). Data from these participants will be combined with that being 
collected in another weight loss trial at the University of Colorado, Anschutz Medical Campus 
(COMIRB, 17-0369, PI, Catenacci) for statistical analysis, and thus are not included as outcome 
measures in the current protocol. Furthermore, the enrollment numbers for the main study do not 
need to be increased, as the target sample size for the sub-study research will not be reached from 
this study alone, and we will only target recruiting as many possible within the target enrollment for 
the main study. 
 
Description:  A subset of 5-10 eumenorrheic (regularly cycling), pre-menopausal women not using 
hormonal birth control will undergo these optional additional procedures.  Daily urine samples will 
collected over a complete menstrual cycle at baseline, and over 3 menstrual cycles at the 
beginning of the study (around months 1-3 of the intervention).  Participants will be provided 
menstrual calendars to document overall menstrual cycle length during the weight loss intervention. 
During the urine collection period, they will be asked to collect daily, first void urine samples over 
the full menstrual cycle.  Urine collection procedures will be based on those utilized by Dr. Santoro 
(co-mentor) in a large (n = 847) cohort study38, and those currently being used in 17-0369. 
Specimen collection kits, including a supply of pre-labeled polypropylene tubes (pre-filled with 
glycerol to a final concentration of 7%), an indelible marker pen, disposable plastic cups, and 
storage boxes will be provided to participants. Women will be instructed to collect their first morning 
voided urine into a cup, fill two tubes to the indicated line (5 ml), and place each tub into a box in 
the freezer within 2 hours of collection. A specimen log will be provided to allow participants to 
record any irregularities in the collection, such as a failure to remember to freeze the tube within 2 
hours. Women will be instructed to collect specimens from the 1st day of menstrual bleeding to the 
1st day of bleeding. Weekly telephone calls, SMS texts, or emails will be performed to encourage 
adherence to the protocol and answer any questions that may arise. Urine samples will be assayed 
in Dr. Santoro’s laboratory for progesterone and estrogen metabolites (pregnanediol 3-glucuronide 
[Pdg], and estrone conjugates [E1c]), and mid-cycle LH and FSH using a flurometric immunoassay 
(AutoDELFIA; Perkin Elmer & Centaur XP; Siemans). Urinary concentrations of Pdg and E1c are 
closely correlated with serum concentrations of estradiol and progesterone allowing for frequent, 

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minimally intrusive data collection. In addition, a tube of blood will be collected during the screening 
blood draw among these participants, and will be stored and assayed for Total Testosterone and 
Anti-Mullerian Hormone (AMH). This will allow us to examine predictors of obesity-related HPO 
axis suppression, and the effects of the behavioral weight loss intervention on HPO axis function 
distinct from the dysregulation of reproductive hormones associated with polycystic ovarian 
syndrome (PCOS).  If, for whatever reason an additional tube of blood was not collected at a 
participants’ screening visit, they will be asked to provide an additional blood draw in order to 
measure these assays. We will control for these hormone levels statistically, or potentially exclude 
data from participants whose labs are consistent with PCOS (AMH ≤ 6, serum Total Testosterone 
<100 ng/dL), whichever approach is deemed most appropriate. 
Justification for Inclusion. Gonadotropins and ovarian hormones are considered key regulators of 
energy homeostasis and body composition among women, and are suppressed in response to 
energy restriction, which reflects an adaptive response to strategically shift energy away from 
reproduction and toward survival during resource scarcity.  Given the limited success of current 
behavioral approaches to treat obesity in women, it is important to evaluate whether 
compensatory mechanisms have evolved to protect reproduction during times of reduced energy 
intake that make weight loss more difficult and explain some of the variability in weight loss 
response.  Thus, we will evaluate whether changes in reproductive hormones impact weight loss 
response, as well as explore whether diet patterns or weight reduction may induce changes in 
levels of reproductive hormones in a subset of eumenorrheic, pre-menopausal women not using 
hormonal birth control.  
 
Recruitment. Male and female enrollment will rely on recruitment strategies that have proven 
successful in attracting volunteers to other projects the mentor and applicant have conducted, 
including projects involving controlled feeding. The recruitment strategies will include:  
 
-Fliers sent to households meeting specified demographics in geographic regions proximal to the 
University of Colorado (CU) Anschutz Medical Campus (AMC);  
 
-E-mail bulletins – system-wide (e.g., CU AMC and University of Colorado Hospital [UCH]) e-mail 
blasts  
 
-Suburban newspaper advertisements – there are many suburban journals in the Metro area that 
are issued on a weekly or monthly basis; we specifically advertise in those that target 
neighborhoods in relative proximity to CU AMC and those that target persons from under-
represented minority groups;  
 
-Major newspaper advertisements – the major publication in the Denver Metropolitan area has a 
Health and Fitness section that runs once per week; advertisements in these sections have 
targeted appropriate individuals for our previous studies;  
 
-University advertisements – advertisements will be placed on a quarterly basis in the two CU AMC 
publications that target students/faculty/staff;  
 
-Community lectures – the investigators participate in a CU AMC-sponsored health-related lecture 
series for the community;  
 
-Participation in health fairs and walk-in health clinics;  
 
Using these methods, the investigative team has previously been successful in recruiting study 
populations with demographics similar to the surrounding Denver metropolitan area. 
 
Pre-screening: Information for the pre-screening of potential subjects during the initial phase of 
recruitment will be collected and managed using REDCap (Research Electronic Data Capture) 

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Survey. REDCap is a secure, HIPAA compliant web application designed to support data capture 
for research studies. Upon completion of REDCap and determination of qualification by research 
personnel, volunteer subjects will receive a detailed explanation of the procedures involved in the 
study at a consent appointment. Individuals who meet the eligibility criteria for the optional 
Reproductive Hormone Sub-study will be identified in the pre-screening by research personnel, and 
will be given a detailed explanation of the procedures and an opportunity to separately consent to 
the sub-study during the consent appointment.  
 
Consent. The consent process is part of the first orientation session, which takes about 1hr. 
Volunteers are either sent a copy of the consent form in advance or, if necessary, are given one at 
the start of the orientation; time is allowed to fully review of the consent form. Volunteers then meet 
with a member of the research team to a) have the study and what is expected of them explained 
in detail; b) discuss their reasons and motivation for wanting to participate to determine whether 
they are realistic; c) discuss any practical problems (e.g., scheduling conflicts, vacations) that could 
interfere with participation; d) have their questions answered; and e) demonstrate their ability to 
provide informed consent by describing their understanding of the major study goals and what is 
expected of them if they choose to participate. To avoid coercion, the presentation will stress that, 
1) all research participation is voluntary, 2) subjects may withdraw at any time, and 3) the decision 
to participate or not participate will not affect the subjects' medical care or any benefits to which the 
subject is entitled. 
 
Compensation. Subjects will be compensated up to $400 for participation in the study. The 
compensation will be prorated as follows:  Subjects will receive $100 for completing the behavioral 
weight loss program and performing assessments at the 12 week time point and $100 at the 6 
month follow up visit.  Subjects who choose to participate in the optional overnight PSG and 
nocturnal metabolism study will be compensated $100 per study day, or a total of $200. Subjects 
who choose to participate in the optional reproductive hormone sub-study will be compensated up 
to $305 for participation in the study. Subjects will receive $70/month of complete (>80%) daily 
urine collection, plus $25 for tracking and reporting menstrual cycle length with menstrual 
calendars.  In addition, participants who agree to participate in the focus groups at the end of the 
intervention will be compensated for their time in the form of $50 Amazon gift cards.  
 
Potential Benefits to Study Participation. The potential benefits to an individual participant in the 
study are not known. Subjects enrolled in this study will potentially benefit by learning information 
about their health status. Subjects will receive information on test results including body 
composition, blood glucose profile, sleep, exercise patterns, energy expenditure and metabolic rate 
and any of the study information they may be interested in. Subjects will also learn information on 
body weight regulation through their participation. Subjects will also receive some compensation. 
The potential benefits of the study to the adult population in general could be significant. The study 
is expected to lead to new data on the relationships between physiological variables relevant to 
weight regulation and weight regain following weight loss. This information will inform future 
strategies for the prevention of weight regain. In light of these potential benefits, the risks to 
subjects are considered acceptable. 
 
D.   Description, Risks and Justification of Procedures and Data Collection Tools: 
 
Risks 
Extended daily fasting: Subjects will be asked to fast prior to the screening visit for a blood draw 
and resting metabolic rate measurement. Due to the extra testing procedures, the fasting period 
may extend beyond a person's habitual overnight fast. In addition, subjects randomized to the TRF 
+ RCD arm of the study will be asked to extend fasting duration to 14 hours/day for 12 weeks. 
Extended fasting may result in irritability, nausea, light-headedness. 
DXA: The DXA (to assess body composition) procedure involves exposure to ionizing radiation. 
DXA measurements (3 time points during the study for each subject) involve a total effective 

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radiation exposure that is roughly equivalent to spending 4 days outside in Denver (<50 mrems), or 
about <1% of the annual allowable exposure for radiation workers. Having trained technician’s 
conduct the DXA scans, thereby reducing the likelihood of needing repeat assessments, minimizes 
this risk.  
Continuous glucose monitoring: The Libre Freestyle Pro CGM sensor measures and stores 
glucose readings when worn on the body. It initially comes in two parts: one part is in the Sensor 
Pack and the other part is in the Sensor Applicator. By following the instructions, the Sensor is 
applied on the back of the patient’s upper arm. The Sensor has a small, flexible tip that is inserted 
just under the skin. The Sensor can be worn for up to 14 days (although a shorter 7 day 
measurement period will be used in the present study). In a clinical study conducted in 4 centers 
and including 72 adults, there were no device-related serious adverse events. Mild skin irritation, 
such as erythema, edema, rash, bleeding, itching, bruising, scaling skin, and induration were 
reported around the insertion site and adhesive area by a moderate frequency of subjects (26 out 
of 72 or 36%). Pain was mostly reported as none with only one reported instance of mild pain. 
Venipuncture: Venipuncture will be performed to obtain the screening blood sample. Approximately 
10 ml of blood will be removed by putting a needle into a forearm vein. This is the standard medical 
procedure for obtaining a sample for blood tests. Subjects may temporarily experience pain or 
discomfort when the needle goes into the vein, but this should subside once the needle is in the 
vein. A bruise may form at the site after the needle is removed.  
Sleep measurement (PSG): Measurement of the electrocardiogram (ECG-heart tracing) may cause 
some skin irritation from the sensors.  Measurement of the electroencephalogram (EEG-brain wave 
activity), Electroocculogram (EOG-eye movement activity) Electromyogram (EMG-muscle activity 
on the chin and legs), nasal-oral air thermister (breathing in and out of the nose & mouth), and 
respiratory bands placed over the chest and abdomen, may cause some minor discomfort and/or 
skin irritation due to the paste used to attach the sensors.  In addition, the paste used to hold 
sensors to the scalp may leave a flaky residue for several days. The physiological recording device 
is electrically isolated and complies with hospital standards for electrical safety.  
Whole room calorimeter: Claustrophobia or noisiness in the calorimeter may disturb volunteers. 
However, the new room calorimeter at UC is large (12’ x 12’) with a large picture window, and 
claustrophobia has never been reported. Furthermore, potential volunteers will be shown the 
calorimeter during the screening to familiarize them with the calorimeter. 
Behavioral weight loss program: While exercise and diet recommendations are based on the best 
evidence and extensive investigator experience, some participants may experience adverse effects 
of either dietary change or exercise recommendations. Subjects are informed of this risk. We will 
minimize these risks through close monitoring by the study investigators. 
Economic risks: Possibility of finding a previously undiagnosed medical condition during screening 
and not having insurance coverage for further evaluation and treatment, as well as time lost from 
work or studies. Minimized by ensuring subjects are in an appropriate economic position to 
participate 
Psychological risks: may involve the stress of identifying a previous unknown medical condition 
during the pre-screening selection. 
Confidentiality and privacy: The use of questionnaires, interviews, and collection of personal 
medical information poses a risk to confidentiality and privacy. 
Optional Reproductive Hormones Sub-Study: The collection of cycle length and urine samples for 
assessment of reproductive hormones could identify a factor which predicts weight loss response 
and carries no known risk.    
 
Protection against Risk 
Risks of study related complications will be reduced by carefully selecting participants for 
participation. We have clearly defined the contraindications to participation. Every effort will be 
made to minimize risks including a review of participants’ health before the testing. A baseline 

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biochemical profile (CBC, Chemistry panel including liver function tests, fasting glucose, TSH) 
along with blood pressure, heart rate, weight and height will be obtained at baseline. The study 
physician will contact the family physician, as needed, to clarify any issues that arise. The risk of 
finding a previously undiagnosed medical condition will be explained clearly as part of the informed 
consent, with the possibility that the condition(s) might require follow-up evaluation and treatment. 
This study will be scheduled to minimize time lost from work or studies, and subjects will receive 
some compensation for the time involved in completing the studies detailed herein. 
Members of the Research team including the nursing staff on the CTRC are trained and 
experienced in all of the methods and measures that will be performed. These measures will be 
performed in a controlled clinical environment (the CTRC) with access to a full complement of 
hospital services. As discussed above, patients without significant co-morbidities will be recruited 
for this study to minimize the risks of serious adverse events.  
Extended daily fasting: Participants will be allowed to eat food following the resting metabolic rate 
test performed at the screening visit. Participants will be encouraged to bring a snack to the visit, 
but the CTRC can provide a granola bar and juice. Subjects randomized to the TRF+RCD group 
will be informed of the potential risks and discomforts associated with extended daily fasting prior to 
starting the behavioral weight loss intervention. Tolerance to the TRF + RCD will be evaluated 
weekly during the behavioral weight loss program and support will be provided to help subjects 
manage hunger and cravings.  
DXA: The risk of radiation exposure is minimized by having trained technicians administer the 
procedures, thereby reducing the likelihood of needing repeat assessments. Scans will not be 
performed in pregnant women. Urine pregnancy tests will be done and verified as negative before 
DXA scans are done on women of reproductive age.  
Continuous glucose monitoring: Subjects will be informed that the CGM sensor may cause from 
minor skin discomfort and/or skin irritation.  
Venipuncture and blood draws: Subjects will be asked not to donate blood or have blood drawn for 
any other studies (unless medically necessary) for prior to and following completion of this study to 
minimize risk of anemia. During venipuncture and catheter placement, standard sterile technique 
will be utilized and experienced phlebotomists and/or nursing staff will perform venipuncture and 
sampling catheter placement to minimize bleeding, thrombosis and infection at the puncture site.  
Sleep measurement (PSG): Subjects will be informed that measurement of the electrocardiogram 
(ECG) and electroencephalogram (EEG), electromyogram (EMG), electrooculogram (EOG), nasal-
oral air thermister and nasal cannula (breathing in and out of the nose & mouth/nasal pressure), 
respiratory bands placed over the chest and abdomen, may cause some minor discomfort and/or 
skin irritation due to the paste used to attach the electrodes. Subjects will be informed that the 
paste used to hold electrodes to the scalp may leave a flaky residue for several days. Aveno cream 
can be used to help treat skin irritation.  Nasal-oral air thermister, nasal cannula and respiratory 
bands can be adjusted if uncomfortable. 
Behavioral weight loss program: We will minimize risks through close monitoring by the study 
investigators and staff members conducting the weight loss program (weekly contact).  
Psychological risks will be minimized by explaining this as being part of the informed consent and 
making sure that if a significant medical condition is diagnosed as part of the screening, every effort 
will be made to explain the condition to the subject, with recommendations for follow-up. The stress 
of physical procedures will be minimized by explaining each procedure as clearly as possible prior 
to and during the procedure, and having experienced staff perform the invasive procedures.  
Data and Safety Monitoring Plan (DSMP) 
The safety monitoring will be performed by the research team, with oversight by an independent 
local Safety Officer.  This is an investigator-initiated study being conducted at a single site. The 
risks in this study are minimized by the use of extensive inclusion and exclusion criteria, and by 
close monitoring of the research subjects. In addition, the involved researchers are qualified and 
experienced in all of the study procedures. Nonetheless, since this study places the subjects at 

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more than minimal risk, we will utilize the services of a volunteer to serve as a Safety Officer at UC. 
The PIs, COMIRB, and Independent Study Monitors (Safety Officer and CTRC Research Subjects 
Advocates) will share the primary responsibility for monitoring study data and safety. The DSMP 
has been developed with the input from the Independent Monitors. 
Roles and responsibilities of the Safety Officer (SO). The safety officer will periodically review 
safety data and judge whether the overall safety of the trial remains acceptable. Any 
recommendations to alter study conduct will be based on safety not efficacy; hence, there is no 
cost to the sample size, power, or final alpha level of the analysis.  The SO will specifically review 
all serious adverse events (SAEs) and summary reports of all adverse events. The sponsor and/or 
applicant may also make recommendations to the SO for additional data review should a concern 
arise. The SO may recommend a new course of action for a specific treatment group or may 
suggest other appropriate courses of action to address general study safety issues that may arise. 
If warranted, the SO may recommend that the protocol be modified, suspended temporarily, or 
terminated permanently. The SO will meet in an open format with the study team every year to 
review the study progress.  
The SO will review the following data: adverse events, recruitment and enrollment statistics, race 
and ethnicity statistics, disqualified and excluded individuals, study progress timeline, procedures 
for data quality control and safety data (e.g. screening labs, enrollment, inclusion and exclusion 
criteria, adverse events). The data will be “frozen” 2 to 4 weeks before the SO review and the data 
will be sent to the SO approximately 7 days before the SO review. Based on the review the SO 
may recommend alterations or changes to the protocol.  Meeting minutes will be prepared by the PI 
of the project and approved by the SO. The minutes will be sent to: CTRC, COMIRB (annually), 
research team, and NIH (with annual progress report).  
Defining and reporting serious adverse events (SAEs). We will utilize the Common 
Terminology Criteria for defining Adverse Events (CTCAE). Adverse events will be graded as mild 
(Grade 1), moderate (Grade 2), severe (Grade 3), or life-threatening (Grade 4), with specific 
parameters according to the organ system involved. We will promptly notify the IRB (within 5 days 
of the occurrence) when unexpected SAEs occur, defined as death (Grade 5), life threatening 
illness, hospitalization or prolongation of hospitalization, congenital anomaly/birth defects, and 
persistent/significant disability. The IRB requires that any SAE that is unexpected and related or 
possibly related to the research intervention be reported. SAEs that are unrelated to the research 
intervention do not have to be reported to the IRB. Risks that are described in the protocol and 
consent do not have to be reported promptly to the IRB unless they occur more frequently or are 
more serious than expected. One exception to this rule is in the case of a death. All deaths must be 
reported, whether or not the death was related to the research. 
Withdrawals and terminations. All withdrawals and terminations will be reviewed by the 
researchers involved in this proposed study and I on a case-by-case basis. The data will be 
scrutinized separately to assessment for association of the interventions with a specific adverse 
outcome. An individual subject may be terminated from the study based on the criteria listed below. 
Any subject that is terminated from the study based on these criteria will be reported to the 
COMIRB during the annual continuing review. 
• 
Request by the volunteer to leave the study 
• 
Evidence of deliberate non-compliance 
• 
Alcohol abuse; illicit drug abuse 
• 
Development of a chronic condition (e.g. Grave’s disease, hypothyroidism, rheumatoid 
arthritis, congestive cardiac failure, or neurological disorders such as MS or stroke) likely to 
impact upon metabolic variables, requiring medications likely to impact upon metabolic 
variables, or impair the ability of the subject to participate 
• 
Development of an acute condition (e.g. myocardial infarction, major depression, accidents 
outside of the study resulting in physical impairments) likely to impact upon metabolic 
variables, requiring medications likely to impact upon metabolic variables, or impair the 
ability of the subject to participate Subjects will be reviewed on a case-by-case basis and 
will be reported to the Data Safety Officer. 

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E.   Potential Scientific Problems:   
 
Adherence to the TRF protocol: This will be the first study to our knowledge that will assess the 
feasibility of using TRF in the context of a reduced calorie diet for weight loss. We will objectively 
measure compliance to the protocol at baseline and 12 weeks using CGM and photographic time-
stamped food logs but will otherwise not know whether subjects randomized to the TRF group were 
compliant to the protocol. To limit the extent of possible non-compliance to the TRF arm we 
decided on a shorter intervention for our first study. We are also using a high intensity behavioral 
support program that will meet weekly to discuss dealing with hunger/cravings or other challenges 
that might be associated with TRF. We will also ask participants to keep a log documenting daily 
feeding duration (first and last energy intake events) during all intervention weeks. 
 
F.   Data Analysis Plan:   
 
Sample Size Justification:. We will aim to recruit 60 participants in two cohorts.. The sample size 
was determined for the primary outcome, change in body weight (kg) at 12 weeks. Assuming 20% 
attrition, we will be left with n=48, or n=24 subjects per group. To justify the sample size, we 
computed the detectable difference that we have 80% power for based on existing preliminary and 
published data. We will assume an alpha=0.05 and use two-sample t-tests. We assumed that the 
RCD group will have similar weight loss as has been shown previously with the standard Colorado 
Weigh curriculum, in which the mean ± standard deviation (SD) weight loss using an intent-to-treat 
analysis at 12 weeks is -4.1 ± 3.7kg57. There are no prior relevant data for 12-week weight loss 
using TRF in the context of a weight loss intervention. However, prior data from the Gill and Panda 
study26 of time restricted feeding without a weight loss intervention showed a mean weight loss at 
16 weeks of -3.3 kg with a SD=3.4 kg. Given that we are combining the RCD and TRF treatments, 
the standard deviation is likely to be between 3.4kg and the sum of the variation of the RCD and 
time restricted studies (SD of the sum = 
 kg ). In our calculation, we assumed for 
the time restricted treatment group (RCD+TRF) a SD in-between the above lower and upper 
bounds of SD at 4.2kg. With these SD’s, we have 80% power to detect a difference in mean weight 
loss between the two treatment groups of 3.5kg. This is slightly larger than the Gill and Panda 
study, but well within the range of the confidence interval of their result. In addition, this calculation 
is quite conservative. We will have power of 80% to detect an even smaller difference in weight 
loss between the groups, because in the final analysis we will adjust for baseline weight, which 
reduces the SD’s in each of the groups and allows us to have power to detect smaller differences.  
The intervention will be modified if we are unable to recruit 30 participants, retain >70% of 
participants, or perform outcome measures within a 2-week window of the indicated time points in 
>90% of participants.  
Statistical Analysis: Efficacy Testing:  Baseline demographic characteristics will be summarized 
by treatment groups using descriptive statistics. Any imbalance between groups will be examined 
using two-sample t-tests and Fisher’s exact tests as appropriate. The primary analysis will use the 
ITT principle to test our study hypotheses under practical and realistic conditions when not all 
participants follow or complete the program. All randomized participants will be analyzed. A linear 
mixed effect model (LMM) will serve as the primary method to handle missing values. The 
normality assumptions will be evaluated and transformations used (e.g. square root and log) as 
appropriate. Change in weight is the primary outcome variable and others will be secondary 
outcomes.  Consequently, no adjustment for multiple outcomes will be applied. P-values <0.05 will 
be considered significant. No interim analysis is planned. Any imbalance in baseline characteristics 
between groups that could potentially be a confounding factor for the outcome will be adjusted for 
in the statistical model (i.e., age, sex, level of PA achieved during intervention). Differences 
between groups in weight, fat mass, lean mass, MVPA, EI, sleep outcomes, and glucose variability 
will be compared using a LMM. Specifically, the test of time by group interaction will be used to 
assess efficacy. Pearson’s correlations will be used to assess the relationship between sleep and 
nocturnal metabolism outcomes and longitudinal weight regain at 6 months. Variability of Major 

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Outcome Measures: Standard deviation and effect sizes will be determined based on the LMM 
model estimates to assist with planning the large-scale trial.   
 
G.  Summarize Knowledge to be Gained:   
 
The importance of understanding mechanisms underlying the tendency for obese people to regain 
weight after they have lost weight cannot be overstated given the current epidemic of overweight 
and obesity and the prevalence of chronic diseases in the U.S. and other developed countries 
worldwide related to the clinical problem of obesity. Obesity is a major risk factor for many clinical 
conditions including type 2 diabetes, cardiovascular diseases, heart disease, hypertension, cancer, 
arthritis and can lead to premature death and disability. Another major problem posed by the 
overweight/obesity pandemic is the concomitant rise of a cluster of life-shortening risk factors 
referred to as metabolic syndrome. The metabolic syndrome represents a constellation of 
metabolic features including insulin-resistance, dyslipidemia, hypertension, and non-alcoholic fatty 
liver disease. While not regarded as a chronic disease, the metabolic syndrome increases risk of 
developing type 2 diabetes and cardiovascular disease. Altogether 133 million Americans - almost 
1 out of every 2 adults - has at least one chronic illness, which results in 7 out 10 deaths every 
year. Medical costs associated with obesity were estimated at $147 billion; the medical costs for 
people who are obese were $1,429 higher than those of normal weight. In total, 75% of the US 
health care is spent on people with chronic conditions. Many people are able to lose weight but 
weight regain is almost universal following weight loss and is the biggest impediment to addressing 
the obesity epidemic. In this context, the proposed study has strong scientific, clinical, public-health 
and economic relevance.   
Future Directions. Data will be used to optimize the RCD+TRF program delivery and to inform the 
planning of a grant proposal for a large-scale interventional trial to test the efficacy of RCD+TRF as 
compared to standard RCD with respect to body weight, fat mass, PA, metabolic outcomes, 
glucose variability and sleep. Further directions include the evaluation of specific time periods for 
restriction (e.g., earlier vs later during the day), and shorter vs longer duration of restriction. The 
role of baseline eating behaviors, especially chronotype, can be explored in future studies. 
Additionally, it would be of interest to evaluate the use of TRF after weight loss, during the weight 
maintenance period or in individuals with metabolic disease (i.e. T2DM, hyperlipidemia). 
 
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