Energy Expenditure & Activity During & After Exercise-Induced Weight Loss

Study Overview
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Brief Summary
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This project is aimed at determining whether an exercise-based weight loss intervention causes a compensation in some component of energy expenditure such that the increase in measured energy expenditure is less than the added exercise. The study will compare two separate exercise interventions to determine if this is influenced by exercise intensity.

Detailed Description
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The primary aim of this proposed study is to determine how total daily activity thermogenesis (TDAT) and total daily energy expenditure (TDEE) are regulated in obese humans attempting to lose weight and maintain weight loss through exercise. Two exercise interventions will be compared; a structured aerobic exercise program and a walking program. exercise activity thermogenesis (EAT) will be verified, and non-exercise physical activity (NEAT), total daily activity thermogenesis (TDAT), and TDEE will be measured using state-of-the-art technologies. Subjects will be studied during a 6 month intervention period and then during a 6 month follow-up period. It is hypothesized that the walking program will have more favorable effects on TDAT and TDEE during both the intervention and follow-up periods. If the investigators hypotheses are correct, then data from the proposed study could be used to improve the effectiveness of exercise-based weight loss and weight loss maintenance programs.

Official Title
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Energy Expenditure & Activity During & After Exercise-Induced Weight Loss

Conditions
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Obesity

Intervention / Treatment
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* Behavioral: Walking exercise


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria Body mass index (BMI) 30-35.0 kg/m2 Age 18-45 years Weight stable (<2 kg weight fluctuation during previous 6 months) No regular exercise (> 1 bout of exercise/wk or participation in any sporting activities > 1 hr/wk) No self-report of acute or chronic disease (diabetes, heart diseases, and joint problems in particular) No current use of prescribed medications No plans to relocate within the next year No plans for extended travel (> 1 week) within the next 6 months No tobacco use For Females: No evidence of amenorrhea (Regular menstrual cycles of 21-35 days) Pre-menopausal status (self-report, to be confirmed during screening) Pregnancy or lactating within the past year No pregnancy or planned pregnancies; sexually active women of childbearing potential may be enrolled if they have had a tubal ligation or use one of the following means of contraception: condom, diaphragm, oral or implanted contraceptives, or intrauterine device. Women in exclusive relationships with male partners who have had a successful vasectomy will not be required to use any additional means of birth control. Exclusion Criteria: Claustrphobia; Any contraindication(s) to > MRI, e.g. aneurysm, cochlear implant, cardiac pacemaker, or implantable cardiac defibrillator, artificial heart valve, metallic stents, any implantable devices or shunt, weight less than 300 lbs; Left Handed.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 55 Years

Sexes Eligible for Study
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All

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: Other
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: 1 Exercise<br>Subjects in the EX group will perform supervised exercise 5 d/wk. Exercise will consist primarily of walking on an inclined motor-driven treadmill, but alternate activities will be permitted for 20% of the total exercise sessions (1 of 5 days). Exercise sessions will be preceded by a 5 min warm-up performed at a HR corresponding to 40% of VO2max. The initial exercise duration and intensity at baseline will be 20 minutes at an intensity that elicits a heart rate (HR) corresponding to 60% of VO2max. The target EE will be achieved by a gradual progression of exercise duration and intensity over the first 8 weeks of the exercise program. The target exercise intensity will be the workload corresponding to 75% of VO2max. | Behavioral: Walking exercise<br>* Subjects will be randomly assigned to either a structured, vigorous-intensity endurance exercise training program or an intermittent, low-intensity exercise program. Individualized exercise prescriptions will be designed to target an increase of 2500 kcal/wk, and the theoretical weight loss will be approximately 15 pounds ( 6.8 kg) during the 6 month intervention.<br>|
| Experimental: 2 Walk<br>Subjects in the WALK group will also perform exercise 5 d/wk. Exercise will consist exclusively of walking on level grades, and will be prescribed in two equal duration bouts each day. Subjects in the WALK group will be individually prescribed a walking program based on the EE during moderate intensity walking. The target exercise intensity will be walking speeds corresponding 45% of VO2max. | Behavioral: Walking exercise<br>* Subjects will be randomly assigned to either a structured, vigorous-intensity endurance exercise training program or an intermittent, low-intensity exercise program. Individualized exercise prescriptions will be designed to target an increase of 2500 kcal/wk, and the theoretical weight loss will be approximately 15 pounds ( 6.8 kg) during the 6 month intervention.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Total daily energy expenditure, assessed using doubly labeled water |  | Prior to exercise intervention, and 6 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Total daily activity thermogenesis |  | Prior to exercise intervention, and 6 months | 
| Body weight and composition |  | Prior to exercise intervention, and 6 months |