Lack of sleep is increasingly being linked to the epidemic of obesity in many developed nations, with new research showing that obese people sleep less than their normal weight peers.
The findings throw a new factor into the current debate surrounding obesity, metabolic syndrome and the role of diet.
Insufficient sleep has been associated with changes in hormone levels that may stimulate appetite. This suggests that our stressful lifestyles may be influencing the rise in obesity, not only because of changes to the diet like increasing consumption of fast food, but also as a result of sleep deprivation.
Writing in the 10 January issue of Archives of Internal Medicine (165: pp25-30), Robert D. Vorona from Eastern Virginia Medical School, Norfolk, and colleagues report that the total sleep time of 1000 people per 24 hours decreased inversely in proportion with their body mass index.
Patients with a normal BMI slept 16 minutes more per day than obese patients.
"Our findings suggest that major extensions of sleep time may not be necessary, as an extra 20 minutes of sleep per night seems to be associated with a lower BMI," said the authors.
Last month a population study by University of Bristol researchers found that people who habitually slept for five hours had 15 per cent more ghrelin, a hormone which increases feelings of hunger, than those who slept for eight hours.
Those who slept for less time were also found to have 15 per cent less leptin, a hormone which suppresses appetite.
The US authors noted that their study does not establish a cause-and-effect relationship between restricted sleep and obesity.
"Investigations demonstrating success in weight loss via extensions of sleep would help greatly to establish such a relationship," they said.
In an accompanying editorial, Joseph Bass and Fred Turek from Northwestern University write: "In recent years, a new and unexpected 'obesity villain' has emerged, first from laboratory studies and now, as reported by Vorona et al… in population-based studies: insufficient sleep..."
"It is now critical to determine the importance of lack of sufficient sleep during the early formative years in putting our youth on a trajectory toward obesity and the metabolic syndrome--a trajectory that could be altered if sleep loss is indeed playing a role in this epidemic," the authors write.