THURSDAY, Oct. 19, 2006 (HealthDay News) -- A yawning child is more likely to be an overweight child, a new British study finds.
In fact, one researcher says poor sleep may be a prime reason behind the growing epidemic of obesity among kids.
According to Dr. Shahrad Taheri of the University of Bristol, sleeping less disturbs normal metabolism, which may contribute to obesity, insulin resistance, diabetes and cardiovascular disease. Even two to three nights of shortened sleep can have profound effects, he said.
"While obesity occurs because of imbalance between energy intake (calories consumed) and energy expenditure (physical activity), we know very little about the factors that influence each side of the energy balance equation," Taheri said.
Sleep could be an important factor, altering metabolic hormones in such a way that people eat more and also choose the wrong kind of foods. In addition, lack of sleep can cause fatigue, which can reduce physical activity, Taheri said.
In addition, research shows that levels of leptin -- a hormone produced by fat tissue when energy stores are low -- were more than 15 percent lower in those sleeping five hours per night compared with those sleeping up to eight hours. And another hormone, ghrelin -- released by the stomach to signal hunger -- was almost 15 percent higher in those with a five-hour sleep schedule, the British researcher noted.
His report, which reviews the current data on sleep and obesity, was published in the October issue of the Archives of Disease in Childhood.
In one study that included over 13,000 British children followed since birth in Bristol (The Avon Longitudinal Study of Parents and Children), long periods of TV-watching was associated with shorter sleep, Taheri said. Shorter sleep is also associated with spending less time being outdoors and active, he added.
"We also observed that short sleep duration at age 30 months is associated with obesity at age 7 years," Taheri said. "So, sleep is likely to be an important factor for both energy intake and expenditure."
Taheri says the increasing availability of computers, mobile phones, TVs and other gadgets is chipping away even further at the time children have for sleep.
"Obesity is rising alarmingly. We need to urgently address it through preventive measures," Taheri said. "We can easily ensure that distractions to sleep are removed from bedrooms of children. Ensuring adequate sleep in children in combination with healthy diet and physical activity is likely to help prevent obesity," he said.
One expert agreed that sleep might be a big factor in obesity.
"An important point mentioned by Taheri is that data linking restricted sleep and obesity exists for children," said Dr. Robert Daniel Vorona, an associate professor of internal medicine at Eastern Virginia Medical School. "In fact, this data in youngsters might be stronger than similar data in adults."
Those studies do not establish a causal relationship between lack of sleep and obesity, however. But Vorona said alterations in hormones such as leptin and ghrelin could cause increased food intake, and thus be the link between less sleep and obesity.
"Even if sleep loss is much less important than caloric intake and lack of exercise in causing the epidemic of obesity, it still makes sense for physicians to encourage children and adults alike to obtain sufficient sleep," Vorona said.
There's more on helping kids get good sleep at the National Sleep Foundation.