Capsaicinoids: a spicy solution to the management of obesity?

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Changes in energy expenditure resulting from altered body weight.

Rudolph L. Leibel, Michael Rosenbaum, Jules Hirsch (1995)

No current treatment for obesity reliably sustains weight loss, perhaps because compensatory metabolic processes resist the maintenance of the altered body weight. We examined the effects of experimental perturbations of body weight on energy expenditure to determine whether they lead to metabolic changes and whether obese subjects and those who have never been obese respond similarly. We repeatedly measured 24-hour total energy expenditure, resting and nonresting energy expenditure, and the thermic effect of feeding in 18 obese subjects and 23 subjects who had never been obese. The subjects were studied at their usual body weight and after losing 10 to 20 percent of their body weight by underfeeding or gaining 10 percent by overfeeding. Maintenance of a body weight at a level 10 percent or more below the initial weight was associated with a mean (+/- SD) reduction in total energy expenditure of 6 +/- 3 kcal per kilogram of fat-free mass per day in the subjects who had never been obese (P < 0.001) and 8 +/- 5 kcal per kilogram per day in the obese subjects (P < 0.001). Resting energy expenditure and nonresting energy expenditure each decreased 3 to 4 kcal per kilogram of fat-free mass per day in both groups of subjects. Maintenance of body weight at a level 10 percent above the usual weight was associated with an increase in total energy expenditure of 9 +/- 7 kcal per kilogram of fat-free mass per day in the subjects who had never been obese (P < 0.001) and 8 +/- 4 kcal per kilogram per day in the obese subjects (P < 0.001). The thermic effect of feeding and nonresting energy expenditure increased by approximately 1 to 2 and 8 to 9 kcal per kilogram of fat-free mass per day, respectively, after weight gain. These changes in energy expenditure were not related to the degree of adiposity or the sex of the subjects. Maintenance of a reduced or elevated body weight is associated with compensatory changes in energy expenditure, which oppose the maintenance of a body weight that is different from the usual weight. These compensatory changes may account for the poor long-term efficacy of treatments for obesity.

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Insufficient sleep undermines dietary efforts to reduce adiposity.

Arlet V Nedeltcheva, Jennifer M Kilkus, Jacqueline Imperial … (2010)

Sleep loss can modify energy intake and expenditure. To determine whether sleep restriction attenuates the effect of a reduced-calorie diet on excess adiposity. Randomized, 2-period, 2-condition crossover study. University clinical research center and sleep laboratory. 10 overweight nonsmoking adults (3 women and 7 men) with a mean age of 41 years (SD, 5) and a mean body mass index of 27.4 kg/m² (SD, 2.0). 14 days of moderate caloric restriction with 8.5 or 5.5 hours of nighttime sleep opportunity. The primary measure was loss of fat and fat-free body mass. Secondary measures were changes in substrate utilization, energy expenditure, hunger, and 24-hour metabolic hormone concentrations. Sleep curtailment decreased the proportion of weight lost as fat by 55% (1.4 vs. 0.6 kg with 8.5 vs. 5.5 hours of sleep opportunity, respectively; P = 0.043) and increased the loss of fat-free body mass by 60% (1.5 vs. 2.4 kg; P = 0.002). This was accompanied by markers of enhanced neuroendocrine adaptation to caloric restriction, increased hunger, and a shift in relative substrate utilization toward oxidation of less fat. The nature of the study limited its duration and sample size. The amount of human sleep contributes to the maintenance of fat-free body mass at times of decreased energy intake. Lack of sufficient sleep may compromise the efficacy of typical dietary interventions for weight loss and related metabolic risk reduction. National Institutes of Health.

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Short-term sleep loss decreases physical activity under free-living conditions but does not increase food intake under time-deprived laboratory conditions in healthy men.

Manfred Hallschmid, Christian Benedict, Kamila Jauch-Chara … (2009)

Short sleep duration is correlated with an increased risk of developing obesity and cardiovascular disease, but the mechanisms behind this relation are largely unknown. We aimed to test the hypothesis that acute sleep loss decreases physical activity while increasing food intake, thereby shifting 2 crucial behavioral components of energy homeostasis toward weight gain. In 15 healthy, normal-weight men, spontaneous physical activity was registered by accelerometry during the entire experiment, and food intake as well as relevant hormones were assessed during a 15-h daytime period after 2 nights of regular sleep (bed time: 2245-0700) and after 2 nights of restricted sleep (bed time: 0245-0700). Experiments were performed in a crossover design. Sleep restriction significantly decreased physical activity during the daytime spent under free-living conditions after the first night of sleep manipulation (P = 0.008). Also, intensities of physical activity were shifted toward lower levels, with less time spent with intense activities (P = 0.046). Total energy intake, feelings of hunger, and appetite as well as ghrelin and leptin concentrations during day 2 remained unaffected by acute sleep restriction. In contrast to our expectation, short-term sleep loss neither increased food intake nor affected concentrations of the hunger-regulating hormones leptin and ghrelin. However, the observed decrease in daytime physical activity may point to another potentially important behavioral mechanism for the health-impairing influence of sleep loss.