GENEVA — A good night's sleep of 7–8 hours may be a key factor in staying slim, and any deviations from this ideal could cause weight gain, results of a 6-year prospective study suggest.
Of 276 adults who participated in the study, 31% had a weight gain of at least 5 kg during the follow-up period. Short-duration (5–6 hours) and long-duration (9–10 hours) sleepers were 35% and 25% more likely, respectively, to have a 5-kg weight gain, compared with those who slept for 7–8 hours.
“Both shorter and longer sleep duration times can predict higher body weight and fat gain in adults, independent of baseline weight or other covariates,” Jean-Philippe Chaput of Laval University, Quebec City, said at the 16th European Congress on Obesity. Sleep duration should be added to the list of determinants that contribute to weight gain and obesity, he noted.
The investigators evaluated the relationship between sleep duration and subsequent body weight and fat gain in the participants, who were aged 21–64 years. Changes in adiposity indices, including body mass index, waist circumference, percent body fat, and fat mass, were compared.
The risk of developing obesity was elevated for short- and long-duration sleepers, compared with average-duration sleepers, with a 27% and 21% increase in risk, respectively. The data were adjusted for covariates including resting metabolic rate, physical activity, and smoking habits.
Compared with those in the normal-duration sleep group, short and long sleepers had greater increases in waist circumference (58% and 47% more, respectively) and greater weight gain (1.8 kg and 1.5 kg, respectively).
According to Mr. Chaput, the most plausible explanation for the sleep and body weight association is an alteration of hormones, such as leptin and ghrelin. Short sleepers are characterized by low leptin levels and high ghrelin levels, suggesting that a positive caloric balance might occur which could lead to weight gain over time.
The researchers previously investigated the effect of sleep duration on weight in children, finding that short sleep duration increases the risk of overweight and obesity in this population as well.
“Furthermore, short sleep duration favors abdominal adiposity rather than total adiposity in children. This suggests the impact of short sleep duration might be more deleterious than previously thought,” Mr. Chaput said, adding that short sleep duration was the most important risk factor for obesity or overweight in children, followed by parental obesity, watching TV, and physical inactivity.