In a perfect world, you will sleep and wake up at the same time every day of the week and you will get eight hours of shut-eye. But in the real world, you are probably staying in bed longer on weekend mornings because you were up late on a Friday night and are making up for the sleep you missed during the week. Sleeping in for a couple of hours (or more) on a Saturday or Sunday morning may seem like a good idea. It can definitely reduce daytime sleepiness and help you feel less stressed out, but your ability to focus will still be reduced and your internal body clock (circadian rhythm or sleep/wake cycle) might even be disrupted and lead to Sunday night insomnia. It will also not help make up for chronic sleep debt – the difference between the amount of sleep that your body needs and the actual amount that you are getting.

However, according to a study in South Korea, sleeping in on weekends is linked to lower body weight. Researchers used data from a nationwide survey of more than 2,000 people who ranged in age from 19 to 82 years old. In face-to-face interviews, researchers asked participants about their height and weight, weekday and weekend sleep habits, mood and medical conditions. The information collected from interviews was used to determine body mass index (BMI), a measure of weight relative to height, and whether participants engaged in catch-up sleep on weekends. On average, the participants slept 7.3 hours per night and had BMIs of 23, which falls in the healthy range. About 43 percent of people slept longer on weekends by nearly two hours than they did on weekdays. Analysis showed that those who slept-in on weekends had average BMIs of 22.8, while those who did not engage in catch-up sleep averaged 23.1 – a small but statistically significant difference. Moreover, the more catch-up sleep a person got, the lower their BMI came to be, with each additional hour linked to a 0.12 decrease in BMI. Not getting enough sleep can disrupt hormones and metabolism and is known to increase the risk of obesity, researchers write in the journal Sleep.

According to the lead investigator, Dr. Chang-Ho Yun of the Seoul National University Budang Hospital, “If you cannot sleep sufficiently on workdays because of work or social obligations, try to sleep as much as possible on the weekend. It might alleviate the risk of obesity. Weekend sleep extension could be a quick fix to compensate for sleep loss over the week.”

So why do we lose weight when we sleep? The better question is, why do we gain weight when we don’t sleep? There are a number of reasons. When you are tired or sleepy, you tend to do things to make you not feel tired or sleepy. You would probably get coffee at Starbucks or drink an energy drink – these contain incredibly large amounts of sugar. Yes, you will get a good boost of energy, but you’re also getting a lot of calories. A study published in the American Journal of Clinical Nutrition found that people who did not get enough sleep were more prone to late-night snacking. Those same people were also prone to reaching for high-carb snacks. A study at the University of Chicago also found that lack of sleep boosts hunger and unhealthy food choices. Sleep-deprived participants in this study were unable to resist “highly palatable, rewarding snacks,” meaning cookies, candy and chips.

On a personal note, I have always been overweight my whole life, but I have lost some weight recently and am currently at my lowest BMI yet. I have found that adequate sleep not only helps me make better decisions, but also helps me to eat less. Sleep is such a good thing for the body and the brain!


  • Melvin Sanicas

    Physician, Scientist, TED Educator, Writer

    Dr. Melvin Sanicas is a physician - scientist specializing in vaccines, infectious diseases, and global health. He is a 'citizen of the world' who has lived, studied, worked in The Philippines, Malaysia, Singapore, South Africa, Switzerland, Germany, Italy, US, and UK. His op-eds, articles, and blogs have appeared in The World Economic Forum Agenda, The Project Syndicate, Huffington Post, TED Ed, Forbes, El Pais, and in over 40 print and online publications worldwide. He is a partner at the Brighton Collaboration, a Fellow of the Royal Society of Tropical Medicine and Hygiene, and a Fellow of the Royal Society for Public Health.