Effect of Caloric Restriction and Protein Intake on Metabolism and Anabolic Sensitivity

Study Overview
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Brief Summary
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The purpose of this study is to determine if an increased protein intake can attenuate the suppression of metabolic and anabolic hormones during caloric restriction

Detailed Description
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Preliminary testing Prior to the study start, participants will be weighed and body composition will be determined using calipermetry (7 sites) and bioelectrical impedance. Peak oxygen uptake (VO2peak) will be assessed using an incremental exercise test on a bicycle ergometer. Randomization Participants will proceed through each of the following conditions lasting 5 days: CR-LP: Participants will be restricted to 30 kcal/kg FFM/day and protein intake will be low (0.8 g/kg BW/day). CR-HP: Participants will be restricted to 30 kcal/kg FFM/day and protein intake will be high (1.7 g/kg BW/day). CON: Participants will be in energy balance and consume 1.7 g protein/kg BW/day. Diet Prescription Dietary energy intake will be controlled using clinical products and maltodextrin to meet target energy intakes. Participants will received calcium and Vitamin D supplementation throughout the study. Exercise Prescription During all conditions, participants will conduct daily supervised exercise on a bicycle ergometer at an exercise intensity of 60% VO2peak. Exercise duration will be adjusted individually such that exercise energy expenditure will amount to 15 kcal/kg FFM/day. Additional exercise and intense physical activity will be prohibited. Assessments The following assessments will be conducted prior to the start of each condition as well as upon completion of each condition: body weight and composition (impedance), fasting blood draw for assessment of metabolic and anabolic hormones, resting metabolic rate, aerobic fitness (VO2peak), and questionnaires. Washout Once a participant has completed a study condition, participant will be allowed a washout of at least 14 days to allow protein balance to return to baseline (Hoffer & Forse, 1990). During this time, participants will resume their regular diet and physical activity.

Official Title
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Can Increased Dietary Protein Prevent the Suppression of Metabolism and Maintain Anabolic Sensitivity of Bone and Skeletal Muscle During Caloric Restriction?

Conditions
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Weight Loss, Starvation

Intervention / Treatment
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* Other: Caloric Restriction
* Other: Protein
* Other: Exercise
* Dietary Supplement: Calcium and Vitamin D
* Other: Maltodextrin


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: 4 hours/week of purposeful aerobic exercise over the last 3 months Body mass index: 19-25 kg/m2 < 15% body fat Exclusion Criteria: Cardiovascular disease risk factors that would result in greater than low risk Smoking Type I, type II diabetes, or history of high fasting glucose; History of high blood pressure and/or use of medication for hypertension; History of Dyslipidemia, or on lipid-lowering medication; Underlying health condition and/or use of medication that could interfere with any of our study outcomes. History or current diagnosis of a clinical eating disorder Failure to adhere to study protocol

Ages Eligible for Study
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Minimum Age: 19 Years
Maximum Age: 30 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Caloric Restriction and High Protein<br>Participants will be calorie restricted to 30 kcal/kg FFM/day and consume 1.7 g protein/kg BW/day. | Other: Caloric Restriction<br>* Participants will consume 30 kcal/kg FFM/day.<br>Other: Protein<br>* Participants will consume 1.7 g protein/kg BW/day.<br>Other: Exercise<br>* Participants will conduct aerobic exercise designed to expend 15 kcal/kg FFM/day<br>Dietary Supplement: Calcium and Vitamin D<br>* Participants will be provided calcium and vitamin D supplement in order to maintain calcium and Vitamin D intake constant across all study arms<br>Other: Maltodextrin<br>* Participants will be provided with maltodextrin to supplement the liquid diet in order to meet caloric needs within each study arm<br>|
| Active Comparator: Caloric Restriction and Normal Protein<br>Participants will be calorie restricted to 30 kcal/kg FFM/day and consume 0.8 g protein/kg BW/day. | Other: Caloric Restriction<br>* Participants will consume 30 kcal/kg FFM/day.<br>Other: Exercise<br>* Participants will conduct aerobic exercise designed to expend 15 kcal/kg FFM/day<br>Dietary Supplement: Calcium and Vitamin D<br>* Participants will be provided calcium and vitamin D supplement in order to maintain calcium and Vitamin D intake constant across all study arms<br>Other: Maltodextrin<br>* Participants will be provided with maltodextrin to supplement the liquid diet in order to meet caloric needs within each study arm<br>|
| Placebo Comparator: Energy Balance<br>Participants will be in energy balance and consume 1.7 g protein/kg BW/day. | Other: Protein<br>* Participants will consume 1.7 g protein/kg BW/day.<br>Other: Exercise<br>* Participants will conduct aerobic exercise designed to expend 15 kcal/kg FFM/day<br>Dietary Supplement: Calcium and Vitamin D<br>* Participants will be provided calcium and vitamin D supplement in order to maintain calcium and Vitamin D intake constant across all study arms<br>Other: Maltodextrin<br>* Participants will be provided with maltodextrin to supplement the liquid diet in order to meet caloric needs within each study arm<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Resting Metabolic Rate |  | Baseline and day 6 | 
| Change in Circulating IGF-1 |  | Baseline and day 6 | 
| Change in Marker of Bone Formation (P1NP) |  | Baseline and day 6 | 
| Change in Marker of Bone Resorption (CTx) |  | Baseline and day 6 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Body Weight |  | Baseline and day 6 | 
| Change in Body Fat Percentage |  | Baseline and day 6 | 
| Change in Aerobic Fitness (VO2peak) | Analyzed in L/min rather than mL/kg/min to remove influence of weight loss. | Baseline and day 6 | 
| Change in Perceived Hunger | Perceived hunger will be assessed using 0-100 visual analog scales. In this case, 100 means maximum hunger while 0 means minimal hunger. | Baseline and day 6 |