Sleep Loss Lowers Metabolic Rate
Sleep is one of the most neglected aspects of health for most athletes. Not getting a good night’s sleep can not only affect performance but it can also impact your gains in the gym. Studies in volunteers who slept short versus long hours show that sleep reduction was accompanied by increased hunger, higher circulating concentrations of the appetite-stimulating hormone, ghrelin, and reduced levels of the anorexigenic hormone, leptin. To determine whether sleep restriction attenuates the effects of a reduced-calorie diet on excess adiposity, researchers had subjects follow a similar diet but differed the duration of sleep. One group slept 8½ hours per night while the other group slept 5½ hours. Sleep curtailment decreased the fraction of weight lost of fat by 55%and increased the loss of fat-free body mass by 60%. In summary, dieting adults getting 5½ hours of sleep produced a catabolic state characterized by reduced loss of body fat and increased loss of fat-free body mass, accompanied by increased hunger and changes in energy expenditure and the neuroendocrine control of substrate utilization. The findings should make bodybuilders aware that cutting back on sleep while dieting can not only cause a catabolic state but can also hinder fat-loss gains.
In this month’s prestigious Journal of Obesity, researchers reported that sleep loss can result in reduced metabolic rate. Short sleep duration is a significant risk factor for weight gain. Researchers wanted to examine the impact of losing sleep and its effect on metabolism. Resting metabolic rate accounts for the largest proportion of daily total energy requirements in humans. Obese individuals have been found to display the lowest RMR. Previous studies across groups of different populations have found that RMR differs depending on age, sex, and body composition.
Healthy adults participated in a controlled laboratory study. After two baseline sleep nights, subjects were randomized to an experimental:
– 4 hours sleep per night for five nights followed by one night with 12 h recovery sleep) or control condition (10 hours sleep/ per night).
Resting metabolic rate and respiratory quotient were measured using indirect calorimetry in the morning after overnight fasting.
Resting metabolic rate—the largest component of energy expenditure—decreased after sleep restriction (−2.6%) and returned to baseline levels after recovery sleep. Sleep restriction decreased morning resting metabolic rate in healthy adults, suggesting that sleep loss leads to metabolic changes aimed at conserving energy. The researchers concluded that RMR was significantly reduced after 5 days of restricted sleep but it returned to baseline levels after just 1 night of recovery sleep.
Andrea M. Spaeth, David F. Dinges, and Namni Goel. Resting metabolic rate varies by race and by sleep duration. Obesity. Volume 23, Issue 12, pages 2349–2356, December 2015