Lack of Sleep May Promote Obesity

It is known that short-term sleep deprivation increases plasma concentrations of ghrelin (a hormone related to increased appetite) and decreases those of leptin (a hormone related to satiety.)

In a randomized crossover study, researchers studied twelve normally healthy non-obese men to observe the effect of sleep deprivation on energy intake and physical activity. During the first night of each 48-hour session, subjects had either 8 hours (from midnight to 8:00 a.m.) or 4 hours (from 02:00 a.m. to 06:00 a.m.) of sleep. All foods consumed thereafter (jam on buttered toast for breakfast, buffet for lunch, and a free menu for dinner) were eaten ad libitum (with no restrictions.) Physical activity was also recorded. Sensations of hunger, perceived pleasantness of the foods, desire to eat some foods, and sleepiness were also evaluated.

In comparison with the 8-hour sleep session, subjects consumed 559 (22%) more calories on the day after sleep restriction, and hunger was higher before breakfast and dinner. Researchers observed no change in the perceived pleasantness of the foods or in the desire to eat the foods. Physical activity was slightly higher after sleep restriction than after 8 hours of sleep, even though the sensation of sleepiness was more apparent.

In this group of healthy men, one night of reduced sleep led to an increase in food intake and, to a lesser extent, physical activity-related energy expenditure. Although further research is needed to confirm the results of this small study, these results suggest that sleep restriction could be a factor that promotes obesity.

Acute partial sleep deprivation increases food intake in healthy men. Laurent Brondel et al Am J Clin Nutr 91: 1550-1559, 2010.

From Weekly Essentials of Health

Supplemental Zinc Decreases Incidence of Infections in the Elderly

Adults over the age of 55 years are more susceptible to infections, immune dysfunction, increased oxidative stress, and zinc deficiency. Since zinc has anti-inflammatory and antioxidant properties, new research sought to determine the effect of zinc on the incidence of total infections in the elderly. Researchers also tested the effect of zinc on markers of oxidative stress.

A randomized, double-blind, placebo-controlled trial of zinc supplementation was conducted in 50 healthy subjects of both sexes aged 55–87 years. The zinc-supplemented group received 45 mg of zinc orally for 12 months. Incidence of infections during the supplementation period was documented. Plasma zinc concentrations and markers of oxidative stress were measured at the beginning and after supplementation.

After zinc supplementation, the incidence of infections was significantly lower, plasma zinc was significantly higher, and generation of oxidative stress markers was significantly lower in the zinc-supplemented group than in the placebo group.

Zinc supplementation decreases incidence of infections in the elderly: effect of zinc on generation of cytokines and oxidative stress. Prasad AS et al. Am J Clin Nutr 2007 Mar;85(3):837-44.

From the Weekly Essentials of Health