Study of Time-restricted Eating on Weight Loss. A Randomized Controlled Trial of the Effects of Time-restricted Eating on Weight Loss in Obese Subjects.
Phase: NA
Conditions: Obesity, Insulin Resistance
Sponsor: University of California, San Francisco

Study Title: Study of Time-restricted Eating on Weight Loss. A Randomized Controlled Trial of 
the Effects of Time-restricted Eating on Weight Loss in Obese Subjects. 
NCT: 03393195 
Date: May 14th, 2019 
 

Experimental Design: 
This is a pilot study to examine the metabolic effects of TRF in overweight/obese humans.  
100+ overweight/obese (BMI>27,<43kg/m2) male and female subjects over the age of 18 will be 
recruited to participate in this study.  Participants will receive an iHealth Bluetooth connected 
scale to use during the study.  Participants will be randomized to one of two eating plans. 1) 8-
hour eating window: TRF group instructed to limit daily calorie intake between 12:00pm and 
8:00pm each day (only water and black coffee/tea permitted outside of eating window); or 2) 
Consistent meal timing: participants are instructed to eat three structured meals each day 
during specified eating windows (7:00am-11:00am, 11:00am-3:00pm, 4:00pm-10:00pm) Group 
allocation will be provided to subjects using the Eureka mobile research platform, and no 
recommendation on total calorie or macronutrient intake was provided.  Participants will be 
instructed to use their iHealth scales daily, preferably in the morning before their first meal 
(Table 1). The Eureka app will also send adherence surveys, sleep questionnaires, and food 
attitude surveys to participants throughout the study. 
 
Participants who live within 60 miles of UCSF were invited to participate in in-depth metabolic 
testing at UCSF. Immediately prior to study start, participants will go to the Clinical and 
Translational Science Institute (CTSI) clinical research center at the University of California, San 
Francisco (UCSF) in order to collect baseline values for the measurements listed in Table 2.  
Since fasting glucose and insulin measurements will be collected, participants will be instructed 
to fast from 8:00pm the night before.  Additionally, iPhone users will be given the option to use 
the Oura ring for sleep and activity tracking. After 12 weeks, participants will come to the CTSI 
clinic to repeat the baseline measurements.   
 
 
Table 1. Measurements to be collected by subjects at home. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Measurement 
Mode of Collection 
Frequency 
Weight 
Bluetooth Scale 
Daily 
Adherence Survey 
Eureka 
Daily 
Sleeping habits (PSQI) 
Eureka 
Monthly 
Food Attitudes (RED Scale) 
Eureka 
Monthly 

 
 
 
Table 2. Measurements to be acquired at baseline and 12-week follow-up (local subjects only) 
 
Statistical Analysis Plan: 
The primary outcome will be percent change in weight since baseline, measured daily via 
iHealth, in the overall cohort of 100 participants.  To estimate the intention-to-treat effect of 
treatment assignment, we will use a linear mixed model (LMM) with fixed effects for treatment 
assignment, days since baseline (as a continuous variable), and their interaction, and random 
effects for participant and day, with unstructured covariance matrix. The treatment effect will be 
estimated by the fixed effect for the treatment by day interaction, capturing the between-group 
divergence in weight loss trajectories. In sensitivity analyses, we will repeat the analysis after 
Winsorizing outliers, which will be defined as points more than 1.5 times the interquartile range 
below the 25th or above the 75th percentile of the overall distribution.  No adjustment will be 
made to p-values or confidence intervals for multiple comparisons for the primary outcome. 
Questionnaire: Age, Sex, Ethnicity, SES, BMI, 
Physical Anthropometry: Waist Circumference, Waist-to-Hip-Ratio (WHR), Mid-thigh girth, 
bicep girth 
DXA Direct Adiposity Measures: Fat mass (arms, legs, trunk, total), Lean mass (arms, legs, 
trunk, total), percent fat (arms, legs, trunk, total), Volumes (arms, legs, trunk, total), muscle 
mass (appendicular, total) 
DXA Derived Adiposity Measures and Indices: Visceral Adipose Tissue (VAT), 
Subcutaneous Abdominal Adipose Tissue (SAT), Trunk fat to leg fat ratio, Trunk to leg 
volume ratio, fat mass index (FMI), fat-free mass index (FFMI) 
DXA Bone Measures: Bone mass (arms, legs, lumbar spine, total), Bone Mineral Density 
(spine, total) 
Biochemical and Hormonal Markers in Fasting Blood 
Albumin, amylase, bilirubin, BUN, CO2, CPK, creatinine, GGT, LDH, total protein, uric acid 
Insulin Resistance & IGFs: glucose, insulin, HbA1C, BHBA 
Lipid Profile & Lipid-soluble Micronutrients: TG, total cholesterol, HDLC, LDLC, Ca, Cl, Fe, K, 
Mg, Na, Phosphate, 
Liver Enzymes: ALT, AST, ALK 
Questionnaire-based Behaviors on Dietary Intake, Physical Activity, and Cognitive 
Eating 
Dietary Intake (MEC Quantitative Food Frequency Questionnaire): nutrients, food items, food 
groups 
Physical Activity (MEC Physical Activity Questionnaire): total METs, METs for 
moderate/vigorous activities 
Cognitive/Psychological Eating Behaviors (Weight-Related Eating Questionnaire): scores for 
emotional eating, eating in response to external cues, eating with compensatory restraint 
(eating less before/after a big meal), eating with routine restraint (holding back at meals, 
counting calories, dieting) 
Meal frequency and times 
Weight cycling history and parental body shape information 
Strength Isokinetics and Isometrics: peak torque, average peak torque, total work, average 
power, AGON/ANTAG ratio 
Hangrip Strength 
Doubly labeled water technique: Total energy expenditure 
Resting Metabolic Rate 

 
Our secondary outcomes will include body fat, lean mass, fasting glucose, insulin, and HbA1c 
levels, resting metabolic rate, and total energy expenditure, assessed at the baseline and 12-
week clinical visits for a subset of 46 participants.  To estimate the intention to treat effect of 
treatment assignment on changes in these outcomes, we will use LMMs with fixed effects for 
treatment assignment, an indicator for the 12-week visit, and their interaction, and a random 
effects for participant. The treatment effect will be estimated by the interaction. In sensitivity 
analyses, we will repeat these analyses Winsorizing any outliers, defined as in the primary 
analysis.  P-values and confidence intervals will be Bonferroni-corrected for 7 comparisons. 
 
All other outcomes measured at the baseline and 12-week clinical visits will be considered 
exploratory and analyzed using the methods described for the secondary outcomes, without 
penalization for multiple comparisons.