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| by Chase Irons, Personal Trainer |
In my 10 years of personal training I’ve heard all sorts of bizarre and unusual questions and comments about health and fitness. A question that I get far too often, however, is something along the lines of, "How little sleep can I get by with while still being able to function optimally?" It isn't a question limited to personal training, either: at one point or another, all of us have likely wished we didn’t have to sleep so we'd have more time in the day to get things done. More than that, there are even all kinds of products on the market that claim to be able to help us keep going longer on less sleep.
Luckily, scientific research on sleep and its effects on the body are plentiful. In a 2010 study, researchers sought to determine whether a combination of sleep deprivation and a moderate caloric deficit would affect results in body composition. For 14 days 3 women and 7 men were instructed to stay in bed for either 8.5 hours or 5.5 hours per night, and their meals were standardized at about 1,450 calories per day. Three months later, the study was repeated for another 14 days with the same participants.
At the end of the study the researchers found that both groups had a nearly the same weight loss of around 6.6 pounds. However, the 8.5 hour group had lost equal amounts of muscle mass and fat mass, while 80% of the sleep-deprived group's loss was lean mass while only 20% was body fat. That means that with all other factors held the same, only a fifth of the sleep-deprived group's weight loss was actually from body fat.
So what exactly is going on in the body to cause this phenomenon? In sleep-deprived individuals there are a few hormones that get knocked out of balance: they produce less leptin, more ghrelin and more cortisol. Decreased production of leptin can make the stomach feel empty. Increased ghrelin production triggers the body's tendency to store fat, reduce the amount of calories it burns, and stimulate hunger. Cortisol is a stress hormone frequently associated with fat gain and muscle wasting, and it also makes us crave sugary and fatty foods. To successfully lose fat we need to optimize leptin, ghrelin and cortisol, but sleep deprivation will make that nearly impossible.
Even if we stick to our diets and hit the gym, sleep deprivation makes it so that the calories we burn come from more from stored energy and less from stored body fat. Because of the muscle-wasting cortisol and the increased hunger because of the lowered leptin and raised ghrelin, it's going to take that much longer to see a positive change in our bodies.
So make it easy on yourself! Get the sleep your body needs so that you aren't working against your goals.
Additional Resources:
Insuffient sleep undermines dietary efforts to reduce adiposity, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2951287/
Impact of Five Nights of Sleep Restriction on Glucose Metabolism, Leptin and Testosterone in Young Adult Men
Impact of Five Nights of Sleep Restriction on Glucose Metabolism, Leptin and Testosterone in Young Adult Men
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0041218
Influence of partial sleep deprivation on energy balance and insulin sensitivity in healthy women.
Influence of partial sleep deprivation on energy balance and insulin sensitivity in healthy women.
Sleep loss results in an elevation of cortisol levels the next evening.
Sleep restriction for 1 week reduces insulin sensitivity in healthy men.
