Weight Loss

Sleep Yourself Skinny

By: Mary Shomon, Thyroid Expert

Average Read Time: 2.5 minutes

If you want to lose weight, what’s the first thing you should do in the morning? If you said, “Lace up my running shoes and head out for a five-mile run” or “Head to the gym,” well, you’re wrong!

Many experts say that the best thing you could do is to pull up the covers, roll over, and catch some more ZZZs.

Researchers are pointing out the proven relationship between what is called “short sleep”—defined as getting less than seven hours of sleep per night—and a long list of metabolic imbalances that make you gain weight, and make it harder to lose weight.

Studies show that short sleep increases your likelihood of obesity by 55%. And short sleep works fast. One study had participants short sleep for just five nights. They gained an average of almost two pounds. In five days!

You can be eating a perfect diet, but if you’re not getting enough sleep, you could be sabotaging your weight loss goals in many ways. 

So what’s really going on?


Fatigue Is Not Your Friend

Sleep makes you physically and mentally tired the next day. And when you’re tired, you move less—you have less energy for physical activity and exercise, which lowers your metabolism. 

On the mental side, short sleep dulls your frontal lobe and activates your brain’s reward centers. That means it’s harder to make good choices about what you eat because your brain desperately craves more high-calorie, high-sugar, and high-fat foods.


The Hormonal Factory Is Only Working Part-Time

Sleep is the time when your body’s hormonal factory goes to work. The thyroid hormone T4 is converted into T3, and growth hormone is released. It’s also a time when your body should burn stored fat to supply continued energy. 

But like any factory, if you shorten the working hours, less work gets done. Short sleep impairs thyroid function by reducing hormone conversion, and leaves you with less growth hormone (which is essential for muscle-building and energy). Additionally, less time sleeping also means less time for fat-burning.


A Hormonal Hurricane

Short sleep increases insulin resistance and raises your cortisol levels. This means that your blood sugar runs higher: There’s more sugar circulating in your bloodstream. High cortisol makes you significantly hungrier. Cortisol also acts as a traffic cop, directing sugar straight to your belly fat cells for extended storage—not burning. Over time, it puts you at a higher risk for diabetes. 

Here’s an example: A study had participants short sleep for just a week. Their insulin levels got so high, and their ability to process glucose so poor, that they were considered pre-diabetic. Now there’s a concept…“7 Days to Diabetes!”

Short sleep also messes with your hunger and satisfaction hormones. Specifically, it increases the hormone ghrelin (which makes you feel hungry), and decreases the hormone leptin (which makes you feel full and satisfied). 

Low leptin levels also increase your craving for—wait for it—sugar! One study found that short sleep resulted in a 15% higher ghrelin level, and almost 16% lower leptin levels.


Loss of Muscle…and Metabolism

Short sleep also directs the body to preferentially burn muscle instead of fat. Muscle is good. It makes us strong and takes up much less space per pound than fat. It also burns more calories at rest than fat. 

Short sleep means that when your body is looking for nighttime energy, it looks to burn muscle cells—instead of fat cells. Less muscle also means a lower resting metabolism.

Short sleep reduces your metabolism. Specifically, it can reduce your resting metabolism, as well as the energy expended after eating. When your metabolism is lower, you gain weight on fewer calories, because your body is burning at a lower rate.

Prioritize Your ZZZs

To sum up: When you sleep less than seven hours a night, you end up feeling hungrier, eating more, having more cravings, feeling less satisfaction and fullness—with less energy to work out, and an impaired ability to make good decisions about what you eat. It makes sense to set that alarm for a little later in the morning!

One caveat though: Research shows that too much sleep (defined as more than nine hours per night) has its own negative health implications. It’s therefore best to aim for seven to nine hours of shut-eye a night to support your weight and health goals.


About the Author

Mary Shomon is a patient advocate and New York Times bestselling author of 13 books on health. Mary has been researching, writing and teaching about thyroid disease, hormonal health, weight loss, and autoimmune disease for two decades. In addition to her books, you can find her writing at www.Verywell.com and www.HealthCentral.com, and catch her PBS Healthy Hormones television specials. Follow Mary on Facebook.