HEALTH NEWS

Study Title:

Lack of Sleep and Poor Dieting Result

Study Abstract

Background: Sleep loss can modify energy intake and expenditure.

Objective: To determine whether sleep restriction attenuates the effect of a reduced-calorie diet on excess adiposity.

Design: Randomized, 2-period, 2-condition crossover study.

Setting: University clinical research center and sleep laboratory.

Patients: 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).

Intervention: 14 days of moderate caloric restriction with 8.5 or 5.5 hours of nighttime sleep opportunity.

Measurements: 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.

Results: 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.

Limitation: The nature of the study limited its duration and sample size.

Conclusion: 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.

From press release:

Researchers from the University of Chicago and the University of Wisconsin-Madison have found that not getting enough sleep may sabotage weight loss efforts because of an association between less sleep and an decrease in fat loss.

The study, published in the latest issue of Annals of Internal Medicine, assigned 10 overweight or obese participants to two groups  one that got 5.5 hours of sleep and another that got 8.5 hours of sleep over two periods, each lasting 14 days. All participants were given the same caloric intake and activity regimens. At the end of the study, researchers found while all subjects lost the same amount of weight, the ones who got less sleep lost less fat and more muscle than the group which got more sleep.

"The loss of lean body mass is an unwanted side-effect of all weight loss diets. This side effect was increased by sleep reduction in our study," said Dr. Plamen Penev, one of the study's authors and an assistant professor of medicine at the University of Chicago Medical Center.

Other sleep and weight loss experts say the study's findings are very significant, since few studies have looked at the relationship between sleep deprivation and metabolism. A study like this one, experts say, adds to the growing body of knowledge on the negative impact of not getting enough sleep. They also say the small size of the study is typical of research that carefully monitors sleep and metabolic processes.

"It suggests that short sleep may confer some negative metabolic consequences," said Gary Foster, director of Temple University's Center for Obesity Research and Education, in Philadelphia, Pa.


Results Suggest Appetite Hormones May Play A Role
In addition to decreased fat loss, the findings suggest that limited sleep may affect levels of two hunger-related hormones, ghrelin and leptin.

"It seems that it's mainly the disregulation in leptin and ghrelin that are driving this," said Dr. Reena Mehra, medical director of the Adult Sleep Lab at University Hospitals Case Medical Center in Cleveland, Ohio.

"The longer you're awake, the hungrier you get," said Dr. Nancy Collop, professor of medicine and director of the Emory Sleep Center in Atlanta, Ga.

Sleep deprivation may also play a role in how the body gets its energy.

"It seems like all this kind of suggests that when people are sleep-deprived, their metabolism changes and breaks down different sources of energy," said Collop. Those sources of energy tend to be carbohydrates and protein rather than fat."

"When you're getting less than 7 to 8 hours of sleep, it may affect metabolism and insulin resistance," said Mehra.

Decreased insulin resistance over a long period of time can potentially lead to diabetes, the experts said.

While they agree that the findings are compelling, sleep and weight loss specialists say that a study with only 10 subjects makes it hard to pinpoint exact causes for decreased fat loss. Nonetheless, they say the study emphasizes how important it is to get a good night's sleep.

"It shows us that we ought to be thinking about ways to incorporate sleep hygiene into standard weight control programs," said Foster.

"Other studies have shown that sleep deprivation can increase risk for cardiovascular disease, weight gain and even mortality," said Mehra. "In a high-pressure society, sleep is one of the things people cut into, and people need to think twice about it and make sure they get enough sleep," she added.

Study Information

Arlet V. Nedeltcheva, Jennifer M. Kilkus, Jacqueline Imperial, Dale A. Schoeller, and Plamen D. Penev.
Insufficient Sleep Undermines Dietary Efforts to Reduce Adiposity
Ann Intern Med
2010 October
University of Chicago and the University of Wisconsin-Madison