The WORLD study is a single-center, year-long randomized controlled trial in free-living women. Participants were randomly assigned to follow either a lower-fat (LF) diet or a moderate-fat (MF) diet for weight management in a parallel-arm design. The two phases of the study were a weight-loss phase (phase 1) and a weight-maintenance phase (phase 2) (Figure 1). During phase 1, months 1 through 4, participants consumed a hypo-caloric diet consistent with the 2005 Dietary Guidelines in the free-living environment. During phase 2, months 5 through 12, participants shifted into weight maintenance. It was hypothesized that a weight-loss intervention at the extremes of dietary fat recommendations of the 2005 Dietary Guidelines would be equally effective for weight loss while achieving comparable nutrient adequacy. Also, Overall, the lower-fat and moderate-fat diets would both be nutritionally adequate, based on the Healthy Eating Index.

Inclusion Criteria:

• 21-50 years
• BMI: 25-39.9 kg/m2
• LDL-C: 100-189.9 mg/dL

Exclusion Criteria:

• Triglycerides > 350 mg/dL
• History of myocardial infarction, stroke, diabetes mellitus, liver disease, kidney disease, and thyroid disease
• High alcohol consumption (<14 drinks/week)
• Use of medication or supplements for lowering blood lipid levels (i.e., statin, fibrates, psyllium, fish oil capsules, soy lecithin, phytoestrogens)
• Lactating, pregnant, or wanting to become pregnant during the study
• Weight loss or gain ≥ 10% body weight in the previous 6 months
• Eating Attitudes Test-26 score > 20
• Beck Depression Inventory-II score ≥ 29
• Gormally Cognitive Factors Related to Binge Eating Scale score > 30
• Physical Activity Readiness Questionnaire score > 2