Dietary intakes associated with successful weight loss and maintenance during the Weight Loss Maintenance trial.

BACKGROUND: Dietary components effective in weight maintenance efforts have not been adequately identified.

OBJECTIVE: To determine the effects of changes in dietary consumption on weight loss and maintenance during the Weight Loss Maintenance clinical trial.

DESIGN: Weight Loss Maintenance was a randomized controlled trial. Successful weight loss participants who completed Phase I of the trial and lost 4 kg were randomized to one of three maintenance intervention arms in Phase II and followed for an additional 30 months.

PARTICIPANTS/SETTING: The multicenter trial was conducted from 2003 through 2007. This substudy included 828 successful weight loss participants.

METHODS: The Block Food Frequency Questionnaire (FFQ) was used to assess nutrient intake levels and food group servings. Carbohydrates, proteins, fats, dietary fiber, fruit/vegetable, and dairy servings were utilized as predictor variables. The FFQ was collected on all participants at study entry (beginning of Phase I). Those randomized to Phase II completed the FFQ at three additional time points: randomization (beginning of Phase II), 12 months, and 30 months.

INTERVENTION: The main intervention focused on long-term maintenance of weight loss using the Dietary Approaches to Hypertension diet. This substudy examined if changes to specific dietary variables were associated with weight loss and maintenance.

STATISTICAL ANALYSES PERFORMED: Linear regression models that adjusted for change in total energy examined the relationship between changes in dietary intake and weight for each time period. Site, age, race, sex, and a race-sex interaction were included as covariates.

RESULTS: Participants who substituted protein for fat lost, on average, 0.33 kg per 6 months during Phase I (P<0.0001) and 0.07 kg per 6 months during Phase II (P<0.0001) per 1% increase in protein. Increased intake of fruits and vegetables was associated with weight loss in Phases I and II: 0.29 kg per 6 months (P<0.0001) and 0.04 kg per 6 months (P=0.0062), respectively, per 1-serving increase. Substitution of carbohydrates for fat and protein for carbohydrates were associated with weight loss during both phases. Increasing dairy intake was associated with significant weight loss during Phase II (-0.17 kg per 6 months per 1-serving increase, P=0.0002), but not during Phase I. Dietary fiber revealed no significant findings.

CONCLUSIONS: Increasing fruits, vegetables, and low-fat dairy may help achieve weight loss and maintenance.