Metabolic adaptation is a phenomenon associated with reduced energy expenditure during and after a prolonged period of caloric restriction. We aren’t sure exactly which component(s) of metabolic adaptation may or may not contribute to weight regain. This recent study specifically evaluated resting metabolic rate (RMR) values before and up to 2 years after weight loss in 171 sedentary, overweight women to see if changes in RMR were associated with weight regain. They also investigated whether or not race influenced the results.
Body weight, body composition, and RMR were measured at baseline, after weight loss, and at 1- and 2-year follow ups. “Metabolic adaptation” was defined as having a measured RMR (RMRm) value lower than the predicted RMR (RMRp).
Average weight loss was around 12kg (~15-16% of initial body weight). RMR values were significantly suppressed by around 50-60 kcal/day after weight loss, but not at 1- or 2-year follow-ups. Subjects regained 52% and 83% of the weight at the 1-year and 2-year follow-ups, but RMR suppression didn’t correlate with weight regain. Generally speaking, white women and black women had pretty similar responses overall.
Suppression of RMR isn’t a reliable predictor of weight regain, most likely because it’s a fairly unremarkable component of metabolic adaptation in the first place. It’d be great for future studies to look at some other components, such as the changes seen in hunger, satiety, non-exercise activity thermogenesis, psychological aspects of eating behavior, and a variety of hormonal changes. Ideally, this research would be done in samples more susceptible to a larger magnitude of metabolic adaptation, like physique athletes or other people who are pushing to get extremely lean. If you want more information about metabolic adaptation and weight regain, be sure to check out our article: The Metabolic Adaptation Manual: Problems, Solutions, and Life After Weight Loss