Metabolic adaptation is not a major barrier to weight-loss maintenance.

Background The existence of metabolic adaptation, at the level of resting metabolic rate (RMR), remains highly controversial, likely due to lack of standardization of participants' energy balance. Moreover, its role as a driver of relapse remains unproven. Objective The main aim was to determine if metabolic adaptation at the level of RMR was present after weight loss and at 1- and 2-y follow-up, with measurements taken under condition of weight stability. A secondary aim was to investigate race differences in metabolic adaptation after weight loss and if this phenomenon was associated with weight regain. Methods A total of 171 overweight women [BMI (kg/m²): 28.3 ± 1.3; age: 35.2 ± 6.3 y; 88 whites and 83 blacks] enrolled in a weight-loss program to achieve a BMI <25, and were followed for 2 y. Body weight and composition (4-compartment model) and RMR (indirect calorimetry) were measured after 4 wk of weight stability at baseline, after weight loss and at 1 and 2 y. Metabolic adaptation was defined as a significantly lower measured compared with predicted RMR (from own regression model). Results Participants lost, on average, 12 ± 2.6 kg and regained 52% ± 38% and 89% ± 54% of their initial weight lost at 1 and 2 y follow-up, respectively. Metabolic adaptation was found after weight loss (−54 ± 105 kcal/d; P  < 0.001), with no difference between races and was positively correlated with fat-mass loss, but not with weight regain, overall. In a subset of women (n  = 46) with data at all time points, metabolic adaptation was present after weight loss, but not at 1- or 2-y follow-up (−43 ± 119, P  = 0.019; −18 ± 134, P  = 0.380; and − 19 ± 166, P  = 0.438 kcal/day respectively). Conclusions In overweight women, metabolic adaptation at the level of RMR is minimal when measurements are taken under conditions of weight stability and does not predict weight regain up to 2 years follow-up. The JULIET study is registered at https://clinicaltrials.gov/ct2/show/NCT00067873 as NCT00067873. [ABSTRACT FROM AUTHOR]