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Slower Metabolism In Fat People Who've Lost Weight (2016 Study)
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Weight loss is accompanied by a slowing of resting metabolic rate (RMR) that is often greater than would be expected based on the measured changes in body composition. This phenomenon is called “metabolic adaptation” or “adaptive thermogenesis,” and it acts to counter weight loss and is thought to contribute to weight regain. Several years ago, we investigated the body composition and RMR changes in 16 people with class III obesity undergoing an intensive diet and exercise intervention as part of “The Biggest Loser” televised weight loss competition. The participants rapidly lost massive amounts of weight, primarily from body fat mass (FM) with relative preservation of fat-free mass (FFM), likely due to the intensive exercise training. RMR was substantially reduced at the end of the competition, indicating a large degree of metabolic adaptation.
Because metabolic adaptation has been suggested to persist for many years following weight loss, we hypothesized that the former “Biggest Loser” participants continued to experience metabolic adaptation years after the competition. We also hypothesized that the degree of metabolic adaptation would be correlated with weight regain. To test these hypotheses, we recruited 14 of the 16 originally studied “Biggest Loser” competitors and measured RMR and body composition changes 6 years after the end of the weight loss competition.
Objective
To measure long-term changes in resting metabolic rate (RMR) and body composition in participants of “The Biggest Loser” competition.
Methods
Body composition was measured by dual energy X-ray absorptiometry, and RMR was determined by indirect calorimetry at baseline, at the end of the 30-week competition and 6 years later. Metabolic adaptation was defined as the residual RMR after adjusting for changes in body composition and age.
Results
Of the 16 “Biggest Loser” competitors originally investigated, 14 participated in this follow-up study. Weight loss at the end of the competition was (mean ± SD) 58.3 ± 24.9 kg (P < 0.0001), and RMR decreased by 610 ± 483 kcal/day (P = 0.0004). After 6 years, 41.0 ± 31.3 kg of the lost weight was regained (P = 0.0002), while RMR was 704 ± 427 kcal/day below baseline (P < 0.0001) and metabolic adaptation was −499 ± 207 kcal/day (P < 0.0001). Weight regain was not significantly correlated with metabolic adaptation at the competition's end (r = −0.1, P = 0.75), but those subjects maintaining greater weight loss at 6 years also experienced greater concurrent metabolic slowing (r = 0.59, P = 0.025).
Conclusions
Metabolic adaptation persists over time and is likely a proportional, but incomplete, response to contemporaneous efforts to reduce body weight.
Because metabolic adaptation has been suggested to persist for many years following weight loss, we hypothesized that the former “Biggest Loser” participants continued to experience metabolic adaptation years after the competition. We also hypothesized that the degree of metabolic adaptation would be correlated with weight regain. To test these hypotheses, we recruited 14 of the 16 originally studied “Biggest Loser” competitors and measured RMR and body composition changes 6 years after the end of the weight loss competition.
Objective
To measure long-term changes in resting metabolic rate (RMR) and body composition in participants of “The Biggest Loser” competition.
Methods
Body composition was measured by dual energy X-ray absorptiometry, and RMR was determined by indirect calorimetry at baseline, at the end of the 30-week competition and 6 years later. Metabolic adaptation was defined as the residual RMR after adjusting for changes in body composition and age.
Results
Of the 16 “Biggest Loser” competitors originally investigated, 14 participated in this follow-up study. Weight loss at the end of the competition was (mean ± SD) 58.3 ± 24.9 kg (P < 0.0001), and RMR decreased by 610 ± 483 kcal/day (P = 0.0004). After 6 years, 41.0 ± 31.3 kg of the lost weight was regained (P = 0.0002), while RMR was 704 ± 427 kcal/day below baseline (P < 0.0001) and metabolic adaptation was −499 ± 207 kcal/day (P < 0.0001). Weight regain was not significantly correlated with metabolic adaptation at the competition's end (r = −0.1, P = 0.75), but those subjects maintaining greater weight loss at 6 years also experienced greater concurrent metabolic slowing (r = 0.59, P = 0.025).
Conclusions
Metabolic adaptation persists over time and is likely a proportional, but incomplete, response to contemporaneous efforts to reduce body weight.
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