Metabolic Adaptation to Weight Loss: Implications for the Athlete

Why a person can eat less, work out harder and not see any reduction in weight – Given restricted calories and then a more intensive workout over a long period of time will lead to adaptation of the body and will plateau any weight loss as a defensive mechanism to protect the metabolic pathways.

Abstract: “Optimized body composition provides a competitive advantage in a variety of sports. Weight reduction is common among athletes aiming to improve their strength-to-mass ratio, locomotive efficiency, or aesthetic appearance. Energy restriction is accompanied by changes in circulating hormones, mitochondrial efficiency, and energy expenditure that serve to minimize the energy deficit, attenuate weight loss, and promote weight regain. The current article reviews the metabolic adaptations observed with weight reduction and provides recommendations for successful weight reduction and long term reduced-weight maintenance in athletes.”

Components of total daily energy expenditure (TDEE). BMR = basal metabolic rate; NEAT = non-exercise activity thermogenesis; TEF = thermic effect of food; EAT = exercise activity thermogenesis; REE = resting energy expenditure; NREE = non-resting energy expenditure. Adapted from Maclean et al., 2011.

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Constantly starving is not a good thing. Working harder and eating less for prolonged periods will induce a stress response in the body that will stop any further weight loss. To combat this, a person should do a surplus of calories infrequently to restore hormonal and other subsequent factors that suffer due to the restrictions. This will resupply the body and enable further weight loss

“To avoid rapid fat gain following the cessation of a diet, “reverse dieting” has also become popular among physique athletes. Such a process involves slowly increasing caloric intake in a stepwise fashion. In theory, providing a small caloric surplus might help to restore circulating hormone levels and energy expenditure toward pre-diet values, while closely matching energy intake to the recovering metabolic rate in an effort to reduce fat accretion. Ideally, such a process would eventually restore circulating hormones and metabolic rate to baseline levels while avoiding rapid fat gain. “

Conclusion: “Weight loss is a common practice in a number of sports. Whether the goal is a higher strength-to-mass ratio, improved aesthetic presentation, or more efficient locomotion, optimizing body composition is advantageous to a wide variety of athletes. As these athletes create an energy deficit and achieve lower body fat levels, their weight loss efforts will be counteracted by a number of metabolic adaptations that may persist throughout weight maintenance. Changes in energy expenditure, mitochondrial efficiency, and circulating hormone concentrations work in concert to attenuate further weight loss and promote the restoration of baseline body mass.

Laura Hobson