The purpose of this study is to test the effectiveness for weight loss and weight maintenance of four diets differing in macronutrient composition: moderate in fat (40 percent energy) with two different protein levels (15 percent and 25 percent), and low in fat (20 percent energy), also with 15 percent and 25 percent protein levels. The study is only accepting participants in the Boston, Massachusetts or Baton Rouge, Louisiana area. For further enrollment information in Boston or Baton Rouge, see Eligibility Criteria or Design Narrative.

BACKGROUND:

Obesity is a growing problem whose importance is reflected in the resources that are expended each year by a large section of the population on weight reduction drugs and therapies. Although numerous weight loss diets are available, there is little agreement in the scientific literature or the lay press as to the amount of fat, protein, and carbohydrates that would comprise the most efficacious diet for weight loss and long term weight loss retention. Reliable information about the effectiveness of low calorie diets with differing macronutrient composition is clearly needed and of paramount importance to inform the choice of a weight reduction diet.

DESIGN NARRATIVE:

The study tests the effectiveness for weight loss and weight maintenance of four diets differing in macronutrient composition: moderate in fat (40% energy) with two different protein levels (15% and 25%), and low in fat (20% energy), also with 15% and 25% protein levels. The moderate-fat diet will be patterned after a Mediterranean diet. All four dietary approaches will be low in saturated fat, and will involve reduction in total energy intake. Each diet is deemed practical and suitable for public health recommendations, and each would be expected to have a favorable effect on cardiovascular disease risk factors. All participants will receive a state-of-the-art behavioral therapy program standardized across the two centers in Boston and Baton Rouge. An estimated 800 men and women, age 30-70 years, body mass index (BMI) 25-40 kg/m2, will be randomized among the 4 dietary treatments. The primary outcome variable will be change in total body weight from baseline to 2 years. Secondary outcomes related to obesity are body fat, BMI, waist circumference, visceral fat, and hepatic and skeletal muscle fat. Other outcomes are psychological factors (diet satisfaction, satiety, food craving, dietary restraint, disinhibition and hunger, and quality of life); major cardiovascular risk factors (blood pressure, low density lipoprotein [LDL] cholesterol, high density lipoprotein [HDL] cholesterol, and triglycerides); prevalence of the metabolic syndrome; blood glucose, insulin, and hemoglobin A1C; emerging cardiovascular risk factors (apolipoprotein B, VLDL and LDL particles with apolipoprotein C-III, lipoprotein[a]); microalbuminuria; and bone mineral content. The primary results will be straightforwardly applicable to public health and clinical guidelines for obesity and will increase our understanding of the biology of obesity and weight loss.

The study is only accepting participants in the Boston, Massachusetts or Baton Rouge, Louisiana area. For Boston participants, contact: 617-998-1047 or www.poundslost.org. For Baton Rouge participants, contact: schoensj@pbrc.edu or 225-763-2623.

Inclusion Criteria:

• Only accepting participants in the Boston, Massachusetts or Baton Rouge, Louisiana area
• Between the ages of 30 - 70
• Willing to modify eating pattern according to instructions
• Overweight or obese and in good health with a BMI of 25-40
• Committed to a long-term weight loss and maintenance program
• Willing to attend multiple weight loss group sessions
• Willing to increase activity level

Exclusion Criteria:

• Pregnant, planning to become pregnant, or are breastfeeding
• Unwilling to participate in the schedule of group sessions and individual visits
• Unstable or recent onset of heart disease or any other serious illness
• Cannot change diet due to medical or other reasons
• Planning to leave the area prior to the anticipated end of participation
• Current participation in another clinical trial with an intervention that affects weight change
• Have diabetes that is treated with insulin or hypoglycemic oral medicines
• Diagnosis of psychiatric or emotional problems within 6 months of study
• Currently have an eating disorder
• Have hypothyroidism
• Have an unstable weight