Metabolic adaptation delays time to reach weight loss goals

Objective The aim of this study was to determine whether metabolic adaptation, at the level of resting metabolic rate, was associated with time to reach weight loss goals, after adjusting for confounders. Methods A total of 65 premenopausal women with overweight (BMI: 28.6 +/- 1.5 kg/m(2); age: 36.4 +/- 5.9 years; 36 were White, and 29 were Black) followed an 800-kcal/d diet until BMI <= 25 kg/m(2). Body weight and composition were measured at baseline and after weight loss. Dietary adherence was calculated from total energy expenditure, determined by double labeled water, and body composition changes. Metabolic adaptation was defined as a significantly lower measured versus predicted resting metabolic rate (from own regression model). A regression model to predict time to reach weight loss goals was developed including target weight loss, energy deficit, dietary adherence, and metabolic adaptation as predictors. Results Participants lost on average 12.5 +/- 3.1 kg (16.1% +/- 3.4%) over 155.1 +/- 49.2 days. Average dietary adherence was 63.6% +/- 31.0%. There was significant metabolic adaptation after weight loss (-46 +/- 113 kcal/d, p = 0.002) and this variable was a significant predictor of time to reach weight loss goals (beta = -0.1, p = 0.041), even after adjusting for confounders (R-2 adjusted = 0.63, p < 0.001). Conclusion In premenopausal women with overweight, metabolic adaptation after a 16% weight loss increases the length of time necessary to achieve weight loss goals.