As I wrote last August, intuition tells us that lack of sleep might contribute to our becoming overweight, but science has yet to confirm that connection or spell out exactly how it might work.
A new bit of evidence — albeit in the form of a very small, as-yet-unpublished study — supporting that link emerged today at an American Heart Association conference in San Diego.
Researchers from the Mayo Clinic observed 17 healthy young men and women (11 men, six women) ages 18 to 40 for 11 days and nights. For eight of those nights, half the group slept the amount of time they normally slept, while the others slept two-thirds of their accustomed time — an average of about 80 minutes less sleep per person per day. All were allowed to eat as much as they chose to. Their calorie consumption and expenditures were measured during the first three days of the study to establish a baseline and then throughout the sleep-deprivation period.
Those in the sleep-deprived group consumed an average of 549 more calories more per day than they did when on their regular sleep schedule. Neither the sleep-deprived group nor the control groups expended more calories during the eight-day study period.
The researchers had surmised beforehand that sleep restriction would lead to reduction in the hunger-suppressing hormone leptin and an increase in the hunger-stimulating hormone ghrelin — changes that together might lead to overeating. They were surprised to find just the opposite: Lack of sleep was associated with increased leptin levels and decreased ghrelin levels, which the researchers say looks “more consistent with a consequence of a positive energy balance than a cause,” according to the study abstract.
Those unexpected findings were among the reasons researchers say further studies are needed. Virend Somers, one of the lead authors, said that those studies should be larger, preferably taking place in people’s homes rather than in a hospital and including actual measures of participants’ weight. Until then, he says, while the study helps tease out the relationship between sleep deprivation (which affects about 27 percent of U.S. adults, according to the abstract) and obesity, there remains “very much a perception” that the two are linked, “but the proof is not present.”