If you’re what researchers call a short sleeper (you sleep for 5.5 to 6 hours or less a night), you’ll have trouble losing weight, no doubt about it. In a 7-year study of 7022 middle-aged people, Finnish researchers found that women who reported sleep problems or had a miss-timed sleep schedule were more likely to experience a major weight gain (defined as 4kgs or more)!
Sleep Less, Burn Less
In a study at the department of neuroendocrinology at the University of Lübeck, Germany, published in the American Journal of Clinical Nutrition, researchers had a group of men sleep for 12 hours a night but didn’t allow them to sleep the next night, and then had them eat an opulent buffet the following morning. Then the researchers measured the subjects’ energy expenditure – the kilojoules you burn just by being. When the men were sleep-deprived, their general energy expenditure was 5 percent less than it was when they got a good night’s sleep, and their post-meal energy expenditure was 20 percent less.
Sleep Less, Eat More
In research presented at the American Heart Association’s 2011 Scientific Sessions, it was shown that women who got only 4 hours of sleep at night ate 1377 additional kilojoules the next day than they did after they slept 9 hours. In another study published in the American Journal of Clinical Nutrition, 11 volunteers spent 14 days at a sleep centre on two occasions. During one period, they slept 5.5 hours a night, and during the other, they slept 8.5 hours. When the subjects were sleep-deprived, they increased their nighttime snacking and were more likely to choose high-carbohydrate snacks.
Sleep Less, Crave More
This is probably the biggest revelation about the connection between sleep and weight loss – and the biggest challenge for you if you’re not getting at least 7 solid hours of sleep each night. Sleeping too little impacts your hormone levels in ways that can undermine the efforts of even the most determined dieter. That’s because insufficient sleep raises the levels of ghrelin, the hormone that tells you to eat. When it comes to weight gain and loss, this hormone plays a leading role. Ghrelin’s job is to boost your appetite, increase fat production, and make your body grow – all of which are fine things if you’re a lanky 12-year-old. But as you get older, ghrelin’s effects can seem pretty darned undesirable. It’s a cinch to figure out why this hormone is the last thing a dieter needs to have circulating in excess.
Lack of sleep also lowers levels of leptin, the hormone that says, “I’m full; put the fork down.” And leptin has a circadian rhythm all its own: Leptin’s levels run high during the night, which tells your body while you’re sleeping that you don’t need to eat. Its levels drop during the day, when you need food as energy. So high leptin levels keep hunger at bay. In studies, for example, mice lost weight because leptin made them eat less and exercise more: the holy grail of dieting. But if you don’t get enough sleep, your leptin levels plummet.
So after even one night of too little sleep, leptin and ghrelin become dietary gremlins bent on diet-wrecking mischief. The lower leptin levels mean that you still feel hungry after you eat. And ghrelin, for its part, magnifies the problem by stimulating your appetite, setting the stage for a day of unsatisfying, high-cal feasting after a restless night.
In the Wisconsin Sleep Cohort Study of more than 1000 people, researchers found that people who got 5 hours of sleep a night had 15.5 percent lower leptin levels and 14.9 percent higher levels of ghrelin, compared with those who got 8 hours of sleep. Know what else the non-sleepers scored higher numbers in? BMI. So more ghrelin plus less leptin equals greater body mass index and weight gain.
Sleep Less, More Time To Eat
It hasn’t been scientifically proven, but some experts believe that the 2 hours or more that we’re no longer using to sleep is giving us another 2 hours to raid the fridge. Instead, get in that bed!