Do adaptive changes in metabolic rate favor weight regain in weight-reduced individuals? An examination of the set-point theory

Abstract

Background: Obese persons generally regain lost weight, suggesting that adaptive metabolic changes favor return to a preset weight. Objective: Our objective was to determine whether adaptive changes in resting metabolic rate (RMR) and thyroid hormones occur in weight-reduced persons, predisposing them to longterm weight gain. Design: Twenty-four overweight, postmenopausal women were studied at a clinical research center in four 10-d study phases: the overweight state (phase 1, energy balance; phase 2, 3350 kJ/d) and after reduction to a normal-weight state (phase 3, 3350 kJ/d; phase 4, energy balance). Weight-reduced women were matched with 24 never-overweight control subjects. After each study phase, assessments included RMR (by indirect calorimetry), body composition (by hydrostatic weighing), serum triiodothyronine (T 3 ), and reverse T 3 (rT 3 ). Body weight was measured 4 y later, without intervention. Results: Body composition-adjusted RMR and T 3 :rT 3 fell during acute (phase 2) and chronic (phase 3) energy restriction (P < 0.01), but returned to baseline in the normal-weight, energybalanced state (phase 4; mean weight loss: 12.9 ± 2.0 kg). RMR among weight-reduced women (4771 ± 414 kJ/d) was not significantly different from that in control subjects (4955 ± 414 kJ/d; P = 0.14), and lower RMR did not predict greater 4-y weight regain (r = 0.27, NS). Conclusions: Energy restriction produces a transient hypothyroid-hypometabolic state that normalizes on return to energybalanced conditions. Failure to establish energy balance after weight loss gives the misleading impression that weight-reduced persons are energy conservative and predisposed to weight regain. Our findings do not provide evidence in support of adaptive metabolic changes as an explanation for the tendency of weight-reduced persons to regain weight.Am J Clin Nutr 2000;72:1088-94.

Oxyntomodulin increases energy expenditure in addition to decreasing energy intake in overweight and obese humans: a randomised controlled trial

“…Although voluntary dietary restriction is a common intervention for obese patients, it is usually accompanied by a decrease in energy expenditure, at least in the short-term. 13 In evolutionary terms, this can be considered an adaptive trait which occurs in order to conserve energy. However, this contributes to the difficulty experienced by obese individuals who attempt to diet A significant increase in plasma insulin was demonstrated after oxyntomodulin injection (***P ¼ 0.0003).…”

“…7 Increased sedentary behaviour is an important factor in the development of human obesity. 10 Whilst low-resting energy expenditure may contribute to obesity, 11,12 recent research has indicated it has minimal impact on weight gain 13,14 and activity-related energy expenditure may be much more important. 15 It has been reported that low physical activity accounted for 77% of weight gain over a year in one prospective study 16 and inactivity is a major determinant of increased adiposity during overfeeding.…”

Effects of energy restriction on activity of the hypothalamo-pituitary-adrenal axis in obese humans and rodents: implications for diet-induced changes in body composition

“…This experimental paradigm enables the effects of weight Brought to you by | University of Sydney Library Authenticated Download Date | 1/24/17 4:17 AM loss per se to be examined, independent of any effects of energy restriction. Indeed, certain adaptations to energy deficit, notably reduced metabolic rate and impaired thyroid function, are seen when measured during energy restriction but not after a period of 10 days to 3 months in energy balance in weight-reduced individuals [58,59]. As such, it is reasonable to propose that HPA axis function may be different depending upon whether it is measured during energy restriction or following a period of weight maintenance at the reduced body weight.…”

What is the required energy deficit per unit weight loss?

“…Such a calculation fails to account for how an individual's energy expenditure adapts to the energy deficit and decreasing body weight and she will therefore not reach her weight loss goal. The magnitude of the expected energy expenditure adaptation during weight loss is a much debated issue [32][33][34][35][36] and has not been addressed in the present study.…”