Youngsters who do not get enough sleep on a regular basis are more likely to be overweight.
Conversely, when children got more shut-eye, they had a reduction in body mass index (BMI) and a significant drop in their risk of being overweight, the researchers found. The investigators also found lower BMIs resulted from differences in fat mass (not any effect on fat-free mass, such as muscle), indicating that poor sleep has negative effects on body composition.
In conducting the study, Rachael Taylor, a research associate professor in the department of human nutrition at the University of Otago in Dunedin, New Zealand, and colleagues followed 244 children from the age of 3 years to 7 years.
Every six months the children's weight, height, BMI and body composition were measured, and their sleep and dietary habits were recorded. The children also wore accelerometers (devices that monitor body movement) to assess their level of physical activity. Additional factors known to be associated with BMI in kids were also taken into account, such as the children's birth weight and their mother's level of education and income.
The study, published online May 26 in BMJ, revealed that the children got an average 11 hours of sleep per day. Those who consistently slept less, however, had an increased risk of having a higher BMI by the time they turned 7 years old. On the other hand, among 3- to 5-year-olds, each extra hour of sleep per night was linked to a reduction in BMI of 0.49 and a 61 percent drop in the risk of being overweight or obese by the age of 7.
Taylor and colleagues concluded that sleep plays a critical role in children's body composition. Prolonged lack of sleep, they found, may cause children to eat more and exercise less. Based on these findings, the study's authors suggested that good sleep habits should be encouraged in children as a matter of public health.
However, more research is needed to determine whether more sleep or better sleeping patterns contribute to healthier children, they noted in a journal news release.