Do you use the weekends to catch up on sleep? If so, you may want to rethink that. In young adults, using weekends to catch up for lost weekday sleep can pose health risks. These include late-night munchies, weight gain and lower sensitivity to insulin (the hormone that controls blood sugar).
“The take-home message is basically that you can’t make up for [lost sleep] by sleeping a few more hours on the weekend,” says Paul Shaw, who was not involved in the study. He’s a neuroscientist at Washington University in St. Louis, Mo. “It’s not as simple as saying, ‘Oh, if I sleep in on the weekends, I’ll be better,’” he says.
Since the 1990s, scientists have understood that missing sleep can harm someone’s health. The changes it causes can lead to obesity and type 2 diabetes. Yet in 2014, a little more than one in every three U.S. adults reported sleeping fewer than the recommended seven hours a night. That’s according to the U.S. Centers for Disease Control and Prevention.
Weekends may seem like a great time to catch up on sleep. Scientists, however, weren’t sure that would work. So Christopher Depner and his colleagues decided to test it out. Depner is a sleep physiologist. He works at the University of Colorado, Boulder.
The team looked at three groups of people in their mid-20s. For roughly two weeks, each group followed a set sleep schedule. One group slept about eight hours every night. Another group only got about five hours of shuteye a night. The third group snoozed some five hours each weeknight, but could sleep whenever and however much they wanted over the weekend.
That last group stayed up until midnight or 1 a.m. on Friday and Saturday nights. The following mornings, they slept in until sometime between 11 a.m. and noon. But they also stayed up late on Sunday. That left them only about six hours of snooze time before the next workweek started. Over the whole weekend, these people got only about 1.1 hours more sleep than what their bodies needed, the researchers found.
“So they did get extra sleep,” Depner notes. But it wasn’t enough to make up for sleep they lost during the week. That what he and his team reported February 28 in Current Biology.
Downsides to too-little or delayed shuteye
People in the study who got too little sleep every night gained weight. So did the weekend sleep-in crowd. By the end of the experiment, people in both groups had gained an average of 1.5 kilograms (3.3 pounds).
Depner says this could be because losing sleep interferes with hormones that control hunger, such as leptin. Since weekend-catch-up sleepers both woke up later and went to bed later, they shifted their body’s internal clocks. As a result, they may have gotten hungry later. During the work weeks, both groups ate roughly 400 to 650 calories in late-night snacks. (Those included foods such as pretzels, yogurt and potato chips.)
But the two groups were different when it came to insulin sensitivity. (If a person is highly sensitive to this hormone, it tells doctors that this person’s metabolism — use of calories — is healthy.) The researchers looked at how all the tissues in the body responded to insulin. Their sensitivity to the hormone fell some 27 percent over the study. That was worse than what was seen in people who slept five hours every night. Their insulin sensitivity dropped only half as much.
After a weekend of playing catch up on sleep, those who had slept too little on weeknights showed significant drops in insulin sensitivity in their liver and muscle cells. Both tissues play an important role in digesting food. Neither of the other two groups responded this way.
“That was very unexpected,” Depner says. Cycling between sleepless weeks and recovery weekends could, all by itself, “have some negative health consequences,” he now suspects.
Peter Liu questions how much these results apply in the real world, especially in people who consistently get little sleep. He is an endocrinologist — a doctor who studies hormones — at the University of California, Los Angeles. In his own research, he’s studied people who report getting too little sleep. Yet he found that a few extra hours of sleep improved their insulin sensitivity. So the latest study, he cautions, “is not the final word on this important topic.”
It seems that resting is “the third pillar of a healthy lifestyle: sleep, exercise and diet,” Liu says. “You wouldn’t say to someone, ‘You need to be on a good diet from Monday to Friday, but on the weekend you can eat whatever you like,’” he notes. “I think it’s the same principle here with sleep.”
average (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.
biology The study of living things. The scientists who study them are known as biologists.
blood sugar The body circulates glucose, a type of simple sugar, in blood to tissues of the body where it will be used as a fuel. The body extracts this simple sugar from breakdown of sugars and starches. However, some diseases, most notably diabetes, can allow an unhealthy concentration of this sugar to build up in blood.
calorie The amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius. It is typically used as a measurement of the energy contained in some defined amount of food. The exception: when referring to the energy in food, the convention is to call a kilocalorie, or 1,000 of these calories, a "calorie." Here, a food calorie is the amount of energy needed to raise 1 kilogram of water 1 degree C.
cell The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.
Centers for Disease Control and Prevention, or CDC An agency of the U.S. Department of Health and Human Services, CDC is charged with protecting public health and safety by working to control and prevent disease, injury and disabilities. It does this by investigating disease outbreaks, tracking exposures by Americans to infections and toxic chemicals, and regularly surveying diet and other habits among a representative cross-section of all Americans.
colleague Someone who works with another; a co-worker or team member.
diabetes A disease where the body either makes too little of the hormone insulin (known as type 1 disease) or ignores the presence of too much insulin when it is present (known as type 2 diabetes).
diet The foods and liquids ingested by an animal to provide the nutrition it needs to grow and maintain health. (verb) To adopt a specific food-intake plan for the purpose of controlling body weight.
endocrinologist A doctor who specializes in conditions affecting the production of hormones or the body’s response to hormones.
hormone (in zoology and medicine) A chemical produced in a gland and then carried in the bloodstream to another part of the body. Hormones control many important body activities, such as growth. Hormones act by triggering or regulating chemical reactions in the body. (in botany) A chemical that serves as a signaling compound that tells cells of a plant when and how to develop, or when to grow old and die.
insulin A hormone produced in the pancreas (an organ that is part of the digestive system) that helps the body use glucose as fuel.
leptin A type of hormone made by fat cells that inhibits hunger.
liver An organ of the body of animals with backbones that performs a number of important functions. It can store fat and sugar as energy, break down harmful substances for excretion by the body, and secrete bile, a greenish fluid released into the gut, where it helps digest fats and neutralize acids.
metabolism (adj. metabolic) The set of life-sustaining chemical reactions that take place inside cells and bigger structures, such as organs. These reactions enable organisms to grow, reproduce, move and otherwise respond to their environments.
muscle A type of tissue used to produce movement by contracting its cells, known as muscle fibers. Muscle is rich in protein, which is why predatory species seek prey containing lots of this tissue.
neuroscientist Someone who studies the structure or function of the brain and other parts of the nervous system.
obesity (adj. obese) Extreme overweight. Obesity is associated with a wide range of health problems, including type 2 diabetes and high blood pressure.
physiologist A scientist who studies the branch of biology that deals with how the bodies of healthy organisms function under normal circumstances.
risk The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)
shuteye Slang for sleep
tissue Made of cells, it is any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.
type 2 diabetes (see also diabetes) A disease caused by the body’s inability to effectively use insulin, a hormone that helps the body process and use sugars. Unless diabetes is controlled, a person faces the risk of heart disease, coma or death.
Journal: C. Depner et al. Ad libitum weekend recovery sleep fails to prevent metabolic dysregulation during a repeating pattern of insufficient sleep and weekend recovery sleep. Current Biology. Vol. 29, March 18, 2019, p. 1. doi: 10.1016/j.cub.2019.01.069.