Very low carbohydrate diets and high-complex carbohydrate, low-fat diets are popular weight-loss methods in the United States. The purpose of the Energy Balance Study is to explore how extreme differences in diet affect eating behaviors, activity and calorie-use, and body composition.

We will conduct a controlled feeding study (all food will be provided for the duration of the study) in which obese adults will be randomly assigned to one of three dietary groups: a low-carbohydrate-eat as much as you like diet, a high-carbohydrate-eat as much as you like diet, or a high-carbohydrate-calorie-restricted diet. The low-carbohydrate diet will be modeled after the Induction Phase of the Atkins Diet. The high carbohydrate diet will be based on the "Dietary Approaches to Stop Hypertension (DASH)" diet. During the first 3 weeks, participants will eat a typical diet adjusted so that they neither gain or lose weight. Then, for 6 weeks, they will eat their assigned research diet. Resting calorie use and body composition measurements will be taken at the end of week 2 and week 9. Frequent blood sampling for 24 hours will be done through a catheter (tube) placed in an arm vein at the end of weeks 2 and week 9 and for 12 hours at the end of week 3.

Change in body composition, activity and energy expenditure, and blood components known to influence eating behavior will be measured under typical diet conditions and after one-day and 6 weeks of the research diet.

Inclusion Criteria:

• BMI; 30-50 kg/m2
• Age at least 21 years
• Relative good health

Exclusion Criteria:

• Major debilitating mental or physical illness that would interfere with participation
• Renal or hepatic disease, diabetes
• History of gallbladder disease/removal
• Hyper-or hypothyroidism
• Poorly controlled hypertension
• Use of lipid lowering medications
• Pregnancy or lactation
• Current excessive use of alcohol
• Current/recent chronic use of tobacco