--- title: Losing Even an Hour of Sleep a Night Is Linked to Weight Gain description: A new study finds that even mild sleep deprivation has noticeable effects on the body. canonical: https://time.com/article/2026/07/08/losing-hour-sleep-linked-to-weight-gain/ author: Veronique Greenwood article:opinion: false article:content_tier: free article:published_time: 2026-07-08T15:47:24.988Z article:modified_time: 2026-07-08T15:47:25.212Z article:section: Health og:title: Losing Even an Hour of Sleep a Night Is Linked to Weight Gain og:description: A new study finds that even mild sleep deprivation has noticeable effects on the body. og:url: https://time.com/article/2026/07/08/losing-hour-sleep-linked-to-weight-gain/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt51c91bb5006af4f8/6a4e6ce6d4269e5d3e9ce08c/GettyImages-2186910886.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 2121 og:image:height: 1193 og:image:alt: GettyImages-2186910886.jpg og:type: article twitter:card: summary_large_image twitter:title: Losing Even an Hour of Sleep a Night Is Linked to Weight Gain twitter:description: A new study finds that even mild sleep deprivation has noticeable effects on the body. twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt51c91bb5006af4f8/6a4e6ce6d4269e5d3e9ce08c/GettyImages-2186910886.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # Losing Even an Hour of Sleep a Night Is Linked to Weight Gain > Sponsored content. 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Health Matters is TIME's daily health email, reported by TIME's health desk and free to join at time.com/newsletters. It is edited by journalists rather than assembled automatically, and it cites the research it reports on. #### Is Health Matters free? Yes. Health Matters is a free daily newsletter from TIME, available at time.com/newsletters. #### Who reads TIME's Health Matters newsletter? Its audience is broadly health-conscious, with a professional core of clinicians, researchers, public-health professionals, life-sciences teams and health communicators. by [Veronique Greenwood](https://time.com/author/veronique-greenwood/) ## Veronique Greenwood Jul 8, 2026 3:47 PM UTC  Kseniya Ovchinnikova—Getty Images by [Veronique Greenwood](https://time.com/author/veronique-greenwood/) ## Veronique Greenwood Jul 8, 2026 3:47 PM UTC It’s common knowledge that [not getting enough sleep is bad for your health](https://time.com/article/2026/04/27/sleep-deprivation-hidden-signs-symptoms/). There are clear [correlations between sleep deprivation](https://time.com/3741436/not-getting-enough-sleep/) and [cardiovascular problems and metabolic conditions](https://time.com/collections/guide-to-sleep/3326565/the-power-of-sleep/). Now, a [new study](http://acpjournals.org/doi/10.7326/ANNALS-25-01660) published in _Annals of Internal Medicine_ finds that even a small amount of sleep deprivation can be consequential: When about 100 people intentionally shorted themselves on sleep for six weeks, their appetite hormones shifted, they burned less energy despite being awake longer, and they gained weight. The findings reinforce the fact that even something that seems as harmless as sleeping for six hours a night instead of seven—roughly what the participants in this study did—has negative effects on the body. ## How much sleep is too little? There have been a number of studies on experimental sleep restriction. In previous experiments conducted in sleep labs, researchers have limited people to just four or five hours a night over a number of days. In fact, [an earlier study](https://pubmed.ncbi.nlm.nih.gov/21715510/) led by one of the researchers behind the latest study required people to sleep less than four hours a night for five days. When they checked at the end, they found that people in the study ate about 300 calories more than they had at the start. This time, the goal was “a more realistic evaluation of what would happen if we asked people to restrict their sleep by 1.5 hours, to a level that's similar to what we generally observe in the population,” says Marie-Pierre St-Onge, director of the Center of Excellence for Sleep and Circadian Research at Columbia University. The optimum amount of sleep varies by individual, but most people need between seven and nine hours a night. In this study, the researchers instructed 95 people, who normally slept around 7.5 hours a night, to go to bed 1.5 hours later than usual for six weeks, while getting up at the same time. They wore wrist monitors and had their blood hormone levels tested, among other measures, to assess any changes happening over the course of the study. The sleep-deprived participants gained about a pound over the six-week period, and their levels of leptin, a hormone linked to body fat, went up. “We found that they spent more time being sedentary during this period of sleep restriction compared to the period of adequate sleep,” says St-Onge. They were awake for longer, but they were less apt to use that time for exercise or moving around. ## Can the effects of sleep deprivation be reversed? The results mesh well with what was already known about sleep and body weight from more extreme experimental studies, says Dr. Sirimon Reutrakul, an endocrinologist and professor of medicine at the University of Illinois College of Medicine who was not involved in the study. If sleep deprivation is harmful, do studies where people are asked to sleep longer show a beneficial effect? Yes, says Reutrakul. She points to a [2022 study](https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2788694?%5F%5Fcf%5Fchl%5Ff%5Ftk=sq3al3IvSiuZLq9umEpv5XvN9ty86H69C3%5FQG%5F7bImY-1783430585-1.0.1.1-YDKJ8KCZ.V6oX6bbFKGkHWdepKQ9Ka3hDyKQkN0v6vk) finding that when people who usually slept too little were asked to sleep more over the course of two weeks, they consumed 270 fewer calories a day. Appetite, sleep, activity—“It’s all interrelated,” she says. That’s the kind of study St-Onge says she might be interested in pursuing. “We're not going to do a study of a longer sleep restriction than what we've done,” she says, because this one had clear results and was tough on the participants. Initially, the team was curious to see whether factors like age might change people’s responses to sleep deprivation. But they couldn’t find enough people to voluntarily forgo a nightly hour of sleep. “We wanted to get more postmenopausal women,” says St-Onge. “They were like, ‘There is no amount of money you can pay me.’” ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/article/2026/07/08/losing-hour-sleep-linked-to-weight-gain/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/article/2026/07/08/losing-hour-sleep-linked-to-weight-gain/"},"headline":"Losing Even an Hour of Sleep a Night Is Linked to Weight Gain","datePublished":"2026-07-08T15:47:24.988Z","dateModified":"2026-07-08T15:47:25.212Z","description":"A new study finds that even mild sleep deprivation has noticeable effects on the body.","url":"https://time.com/article/2026/07/08/losing-hour-sleep-linked-to-weight-gain/","keywords":["Sleep"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/blt51c91bb5006af4f8/6a4e6ce6d4269e5d3e9ce08c/GettyImages-2186910886.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"Veronique Greenwood","jobTitle":"","url":"https://time.com/author/veronique-greenwood/"}],"articleSection":"Health","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/blt51c91bb5006af4f8/6a4e6ce6d4269e5d3e9ce08c/GettyImages-2186910886.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"GettyImages-2186910886.jpg","caption":"","creditText":"Kseniya Ovchinnikova—Getty Images","representativeOfPage":true}],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/health/","name":"Health"}},{"@type":"ListItem","position":2,"item":{"@id":"/tag/sleep/","name":"Sleep"}},{"@type":"ListItem","position":3,"item":{"@id":"https://time.com/article/2026/07/08/losing-hour-sleep-linked-to-weight-gain/","name":"Losing Even an Hour of Sleep a Night Is Linked to Weight Gain"}}]}] ```