The less a child sleeps, the more likely he or she is to become overweight, according to researchers from Universiti Laval's Faculty of Medicine in an article published in the latest edition of the International Journal of Obesity.
The risk of becoming overweight is 3.5 times higher in children who get less sleep than in those who sleep a lot, according to researchers Jean-Philippe Chaput, Marc Brunet, and Angelo Tremblay.
These results come from data collected among 422 grade school students aged 5 to 10. The scientists measured the weight, height, and waist size of each participant. Information on the children's lifestyle and socioeconomic status was obtained through phone interviews with their parents.
Through body mass index measurement, the researchers determined that 20% of the boys and 24% of the girls were overweight. Children who slept less than 10 hours a night were 3.5 times more at risk of being overweight than those who slept 12 or more hours. No other factor analyzed in the study--parental obesity, parents' level of education, family income, time spent in front of the TV or computer, regular physical activity--had as much of an impact on obesity than time spent sleeping.
Hormone production is currently the researchers' prime hypothesis to explain the relationship between sleep and obesity. "Lack of sleep lowers the level of leptin, a hormone that stimulates metabolism and decreases hunger. In addition, short nights of sleep boost the concentration of ghrelin, a hormone that increases hunger," explains Professor Angelo Tremblay.