Adults who cut their sleep by a little over an hour a night for six weeks gained about 0.45 kilograms, or roughly one pound, compared with a period when they kept their normal sleep schedules, according to a recent study by researchers at Columbia University’s Vagelos School of Medicine.
The finding is aimed at a more ordinary kind of sleep loss than the lab-torture version often used in sleep research. Earlier studies have commonly pushed participants down to about four hours of sleep a night, a level that can raise appetite and overeating but is hard for most people to sustain for long. Columbia’s team studied a milder pattern: the kind of five-to-six-hour night that, according to the researchers, affects about 30 percent of adults.
The study followed 95 adults who usually slept at least seven hours daily and had cardiovascular and metabolic risk factors. For one six-week period, participants delayed bedtime by 90 minutes. For another six weeks, they followed their usual sleep routines. Wrist-worn monitors tracked sleep and physical activity, while researchers measured weight, waist size, body composition and fasting blood levels of hormones linked to appetite regulation.
During the restricted-sleep period, actual sleep fell by about 80 minutes. Average weight rose by about a pound compared with the normal-sleep period, according to the Columbia team’s study. The researchers said that if a similar pattern persisted over a year, the accumulated effect could be meaningful for weight.
Less sleep, more sitting
The study also found that participants sat more when they slept less. Average sedentary time increased by 17 minutes per day during the sleep-restricted period. Among men and postmenopausal women, the increase was nearly 30 minutes per day.
That detail matters for the mechanism. The extra waking time did not translate into extra movement. In this experiment, people who stayed up later spent more of that added time sitting, which is exactly the kind of result that makes lifestyle advice sound less like moral philosophy and more like measurement.
The appetite-hormone data did not line up neatly with a common explanation from severe sleep-restriction studies. Leptin, a hormone associated with appetite suppression, was higher during the restricted-sleep period. That means the simple story that less sleep causes weight gain through lower leptin does not fit these data, at least for this group and this degree of sleep loss.
Marie-Pierre St-Onge, a Columbia professor specializing in nutritional medicine, said in a university release that adequate sleep may help reduce the risk of weight gain and obesity-related conditions including heart disease and diabetes.
Earlier signals from the same group
The weight study sits alongside earlier Columbia work using some of the same participants. In one study of 38 women, reducing sleep by about 80 minutes a night for six weeks increased insulin resistance, a risk factor for type 2 diabetes. The effect was stronger in postmenopausal women, according to Columbia.
Another study involving the same participant group found that mild sleep reduction made immune cells in blood more likely to migrate toward sites of inflammation, a possible signal for cardiovascular risk.
St-Onge said Columbia’s findings suggest insufficient sleep raises the risk of obesity-related conditions such as type 2 diabetes and heart disease. She said the next research step is to determine what health benefits chronically sleep-deprived people may get by lengthening their sleep.
This story draws on original reporting from WIRED.
