Long-term Exercise, Weight Loss and Energy Balance

• Between group weight change at 10 months [ Time Frame: 10 months ] [ Designated as safety issue: No ]
  

• Body Composition [ Time Frame: 10 months ] [ Designated as safety issue: Yes ]
  Changes in body composition will be evaluated by measuring the change in percent body fat, total fat mass, and total lean mass by DEXA.
  
  
• Resting Metabolic Rate [ Time Frame: 10 months ] [ Designated as safety issue: No ]
  Resting metabolic rate will be determined via indirect calorimetry following an overnight fast.
  
  
• Total Daily Energy Expenditure [ Time Frame: 10 months ] [ Designated as safety issue: No ]
  Total daily energy expenditure will be determined using the doubly labeled water procedure
  
  

Exercise is recommended by virtually every public health organization; however, the role of exercise is generally considered secondary to energy restriction for the treatment of obesity. Indeed, an argument can be made that suggests exercise is not effective for weight loss. Meta-analytic studies consistently find small amounts of weight loss due to exercise without energy restriction. It is critical to note that there are actually very few randomized controlled trials using exercise alone for weight loss. We believe that there are 3 critical flaws in the vast majority of the literature. 1)Participants are not supervised and is generally recorded by self report and is likely poorly estimated and in general, overestimated. 2)The amount of exercise used is usually prescribed from the guidelines for recommended levels for physical fitness and to diminish cardiovascular disease, not the amount that may be necessary for weight loss. 3)The energy expenditure of the exercise is rarely reported.

Participants will be randomly assigned to expend either 400 or 600kcal per exercise session (or a control group) and will exercise 5 days per week for 9 months. All exercise sessions will be supervised and the length of the exercise session will be based upon energy expenditure (kcal/min) at a give heart rate range. To account for improvements in fitness, energy expenditure will be measured monthly and adjustments to the daily exercise prescription will be altered accordingly.