A lengthy trial that involved robbing people of 90 minutes of sleep per night has uncovered the dramatic effect that even this small amount of lost shut-eye has on the waistline and general health.
Columbia University researchers were particularly interested in examining whether consistently chipping away at an individual’s regular sleep hours could impact weight gain. While sleep and gaining weight have been tied together in many previous studies, a lot of research has focused on more extreme insomnia for shorter periods of time.
And it’s been difficult to pull apart the cause-effect of lack of sleep, because following a bad night, daytime behaviors – less movement, more eating – become skewed. So determining if sleep itself is the factor is challenging.
“These studies only show us what happens under the most extreme conditions and don’t tell us if mildly sleep-deprived people, like a lot of Americans who get five or six hours of sleep a night, will gain weight,” says study leader Marie-Pierre St-Onge, a professor of nutritional medicine in Columbia’s Department of Medicine and Institute for Human Nutrition.
In this new study, the researchers recruited 95 adults who regularly achieved an average of seven to eight hours of sleep a night. The participants were then told to delay their usual bedtimes by 90 minutes, while their waking time remained the same. They did this for six weeks, then completed another six weeks in which they went to bed at their normal, earlier time.
Throughout the study, sleep duration and quality, as well as daytime activity levels, were measured with a wrist monitor. Physical measures of body weight, waist circumference, fat composition, and fasting levels of hormones that impact appetite were also taken.
What they found at the end of the 12 weeks was that during the time of mild deprivation, or around 80 minutes a night for six weeks gained, on average, one pound and were much more sedentary.
“While the one-pound weight gain observed with modest sleep curtailment is not overwhelming, it is important to remember this is occurring over just six weeks,” says first author Faris Zuraikat, assistant professor at Columbia’s Department of Medicine and Institute for Human Nutrition.
“Our study was designed to mimic sleep patterns that most adults experience chronically,” he adds. “When extrapolated to a full year, we would expect that losing less than an hour and a half of sleep per night could result in clinically meaningful weight gain.”
During the initial six weeks, the participants were less active, averaging 17 minutes per day, with activity climbing to almost 30 minutes for men and postmenopausal women.
“Even when we accounted for the fact that they were awake longer when sleep was shortened, participants spent more time being inactive than when they got adequate sleep,” Zuraikat says. “This is notable, as people who are more sedentary have elevated risk for chronic diseases.”
In a related study that focused on a subset of the 95 participants, the team found that women at increased risk of cardiometabolic disease developed signs of increased insulin resistance, a biomarker for type 2 diabetes, after six weeks of shortened sleep.
In another study of this group, both men and women with an increased risk of cardiovascular disease had heightened activity of inflammatory cells in the heart after such mild sleep restrictions.
“Our study shows that getting adequate sleep may help reduce the risk of weight gain and obesity-related conditions like heart disease and diabetes,” says St-Onge.
“Though more research is needed to further understand how sleep restriction leads to weight gain, all of our findings suggest that insufficient sleep increases the risk of obesity-related conditions like type 2 diabetes and heart disease,” she adds. “Now we need to understand the health effects of improving sleep in those who fail to get adequate sleep on a regular basis.”
The study was published in the journal Annals of Internal Medicine.
Source: Columbia University
Fact-checked by Mike McRae
