Many studies examining the link between sleep deprivation and obesity have focused on severe sleep deprivation, such as restricting participants’ sleep to about four hours a night. These studies suggest that this may lead to increased appetite and overeating, which in turn could contribute to weight gain.
Because very few people can endure such severe sleep restrictions for more than a few days, though, the practical utility of this research is limited, and it hasn’t necessarily clarified whether more common and milder types of sleep deprivation, such as getting five to six hours of sleep per night, actually lead to weight gain.
This is the backdrop for a recent study by a research team at Columbia University’s Vagelos School of Medicine, which revealed that chronic, mild sleep deprivation—which is estimated to affect about 30 percent of adults—can lead to weight gain.
“Our study shows that getting adequate sleep may help reduce the risk of weight gain and obesity-related conditions like heart disease and diabetes,” explained Marie-Pierre St-Onge, a professor at Columbia University specializing in nutritional medicine, in a release.
Less Sleep, More Weight
St-Onge and her research team studied 95 adults who typically slept at least seven hours a day and had cardiovascular and metabolic risks. These participants were asked to delay their bedtime by 90 minutes for six weeks, and their sleep duration and physical activity were recorded using wrist-worn monitors.
For another six weeks, the participants maintained their usual sleep schedules. During both periods, the researchers measured the participants’ weight, waist circumference, body composition, and the fasting blood levels of several hormones involved in appetite regulation.
Analysis revealed that during the period when bedtime was delayed and sleep duration was reduced by approximately 80 minutes, participants’ average weight increased by about 0.45 kilogram—about a pound—compared to the period when they slept normally. Extrapolating these results over a year, significant weight gain could be associated with chronic sleep deprivation.
In addition, during the sleep-restricted period, the average amount of time spent sitting increased by 17 minutes per day. When limited to men and postmenopausal women, sedentary time increased by nearly 30 minutes per day. In other words, even accounting for the longer time spent awake, participants spent more time sitting than when they got enough sleep.
On the other hand, levels of leptin—a hormone that suppresses appetite—were actually higher during the period of sleep restriction. The theory put forward by studies on severe sleep restriction that disruptions in hormones leads to overeating does not apply, at least as far as leptin is concerned.
The Next Step
A previous study involving a subset of the same participants (38 women) also demonstrated broader health implications. When women at high risk for cardiovascular and metabolic diseases had their sleep reduced by approximately 80 minutes per night over a six-week period, their insulin resistance—a risk factor for type 2 diabetes—increased. This effect was particularly pronounced in postmenopausal women.
Furthermore, another study involving the same participants showed that a mild reduction in sleep duration among men and women at high risk for heart disease caused immune cells in the blood to become more likely to migrate to sites of inflammation.
This study suggests that even mild sleep deprivation—which many people experience on a daily basis—can have measurable effects on weight, sedentary time, and hormones related to appetite. The finding that the accumulation of even slight sleep deficits can pose a health risk challenges modern lifestyles that tend to prioritize other activities over sleep.
“All of our findings suggest that insufficient sleep increases the risk of obesity-related conditions like type 2 diabetes and heart disease,” St-Onge says. “The next step is to understand what health benefits people who are chronically sleep-deprived can gain by improving their sleep duration.” To what extent can reassessing daily sleep duration help with weight management and the prevention of lifestyle-related diseases? Further research is needed to understand the mechanisms involved.
This story originally appeared on WIRED Japan and has been translated from Japanese.