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

Abstract

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.

Keywords: adaptive thermogenesis; energy expenditure; metabolic adaptation; weight regain.