The Common Sacrifice of Sleep
Sleep is often the first thing we sacrifice. One more email, one more episode, one more scroll, and suddenly it is past midnight. We tell ourselves a lost hour here and there is harmless. Researchers at Columbia University Vagelos College of Physicians and Surgeons wanted to find out if that is actually true.
Study Design: A Small Change in Bedtime
The team recruited 95 healthy adults who normally sleep seven to eight hours a night. Each person moved through two separate six-week phases. In one phase they slept as they always had. In the other, they pushed their usual bedtime back by 90 minutes. That gap is small on purpose. It matches the kind of everyday sleep loss that builds up without anyone deciding to stay up.
What the Trackers Measured
A wrist monitor followed both sleep and movement across every phase. The researchers also recorded body weight, waist circumference, body composition, and fasting levels of several hormones tied to hunger and fullness. Together those numbers gave a fuller picture than a bathroom scale ever could.
Why Mild Sleep Loss Matters
Roughly 30% of adults already live on this kind of trimmed sleep, often without choosing to. Yet most of what we know about sleep and weight comes from harsh studies where people slept only about four hours a night. “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 5 or 6 hours of sleep a night, will gain weight,” said Marie-Pierre St-Onge, a study leader. Severe sleep loss is known to scramble appetite and push people toward overeating. The catch is that almost nobody can keep that up for more than a few days, which leaves a big gap in what the research can tell us.
Results: Weight Gain and Reduced Activity
By the end of the shortened-sleep phase, the volunteers had gained weight. The average gain came to about one pound. “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,” said Faris Zuraikat, first author of the study. “Our study was designed to mimic sleep patterns that most adults experience chronically. 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.” The scale was only half the story. Cutting sleep also nudged people toward moving less during the day. Sedentary time rose by about 17 minutes a day across the whole group. Among men and postmenopausal women, it climbed by nearly 30 minutes. “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 said. “This is notable, as people who are more sedentary have elevated risk for chronic diseases.”
Past Research: Deeper Impacts of Sleep Loss
Earlier work on this same group of volunteers hinted at trouble under the surface. In one study, women with higher cardiometabolic risk who cut their sleep by around 80 minutes showed more insulin resistance. That is an early warning sign for type 2 diabetes. The effect landed hardest on postmenopausal women. A separate study looked straight at the heart. Men and women with elevated heart risk had an influx of inflammatory cells after mild sleep restriction, the kind of low-grade inflammation that tends to travel with heart disease.
What Better Sleep Could Bring
“Our study shows that getting adequate sleep may help reduce the risk of weight gain and obesity-related conditions like heart disease and diabetes,” St-Onge said. “People tend to gain weight over the course of their adulthood, and obesity is a major risk factor for heart disease. But focusing on eating a healthier diet and getting more physical activity to offset weight gain is simplistic and can be difficult to maintain.” The takeaway is not that diet and exercise stop mattering. It is that sleep belongs in the same conversation, and it may be doing quiet work in the background either way. “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,” St-Onge said. “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 is published in the journal Annals of Internal Medicine.