Extra Hour of Sleep Cuts Daily Calorie Intake by 270, Study Finds

A team of researchers at the University of Chicago set out to test something simple: what happens when people who are chronically tired get more sleep? The answer, published in JAMA Internal Medicine, turned out to be surprisingly concrete. Those who managed to sleep an extra hour consumed roughly 270 fewer calories the next day—without being told to diet, without changing what they ate, without exercising differently. The only variable that shifted was sleep itself.

The study enrolled 80 adults between 21 and 40, all carrying extra weight and all sleeping less than the recommended seven hours per night. For at least six months before the study began, these participants had been getting fewer than 6.5 hours of sleep on average. After two weeks of baseline measurement, the researchers split the group in half. One group received personalized sleep coaching from a sleep physician who took into account their work schedules, family obligations, pets, and children—the actual texture of their lives. The other group continued sleeping as they always had.

The intervention worked. Over the next two weeks, the sleep-extended group added an average of 72 minutes to their nightly rest. To measure what this meant for their eating, researchers used a precise method: participants weighed themselves daily at home, underwent body composition testing at the lab, and drank water laced with traceable isotopes so scientists could track their metabolism through urine samples. The math was unambiguous. Those sleeping more consumed about 270 fewer calories per day and lost one pound over the four-week study period. Three participants in the sleep group cut their intake by more than 500 calories daily; one reduced it by more than 750.

The mechanism behind this shift is rooted in how sleep shapes the brain's hunger signals. When people are sleep-deprived, their bodies produce less ghrelin—the hormone that tells you to eat—and more leptin, which signals fullness. The result is counterintuitive: exhausted people feel hungrier. A meta-analysis of previous research found that sleep-deprived individuals consumed an average of 385 more calories than those who slept well. Beyond hormones, poor sleep activates the brain's reward centers in response to high-calorie foods, making fatty and sugary options more appealing. There is also an evolutionary logic to this: a tired body seeks energy, and it seeks it in concentrated form.

Esra Tasali, the study's lead author and director of the University of Chicago's Sleep Research Center, emphasized the potential implications for weight management programs. Yet she and her colleagues were careful about one thing: the intervention they used—personalized sleep consultation with a physician—is not available to everyone. The researchers acknowledged this gap. What people could do on their own, Tasali suggested, is attend to their bedtime routines: putting away phones and tablets before sleep, thinking deliberately about the conditions that help them rest.

The weight loss itself—one pound over a month—is modest. But the finding sits within a much larger body of evidence showing that sleep deprivation disrupts metabolism, appetite regulation, and food choices in ways that accumulate over time. Poor sleep has been linked to obesity, and obesity to chronic disease, though researchers are careful to note that body weight alone tells an incomplete story about health. What this study adds is a mechanism: give people more sleep, and without any conscious effort to restrict calories, they naturally eat less. It is a reminder that sometimes the most powerful health interventions are not about willpower or restriction, but about meeting a basic biological need.