Sleep's impact on weight

Dr. Emmanuel Mignot is professor of psychiatry and behavioral sciences at Stanford University and director of the Stanford Center for Sleep Sciences and Medicine. While he is internationally recognized for discovering the cause of narcolepsy, a disorder caused by hypocretin (orexin) cell loss, Dr. Mignot also studies and treats patients with everyday sleep issues, including one that may surprise readers: the connection between sleep loss and weight gain.

Is there really a correlation between sleep loss and weight gain?

It is very clear that if you’re not sleeping enough, you’re putting yourself at risk for increasing your weight.  If you sleep less than six hours a night, you’re likely to have a higher BMI (body mass index). Longitudinal data — and the evidence is quite strong — shows that if you sleep more over time, you’ll lower your BMI, which correlates with weight reduction.

Why do you think this is?

In the first centuries of human life on earth, if humans weren’t sleeping they were probably looking for food or fleeing a predator. Not sleeping enough was a sign that we were in danger or that we were under stress. When we are sleep deprived, we feel hungry. Data indicates that if you sleep less, you eat more, and it disrupts your hormones. This problem is magnified in today’s world because food is too available! 

If losing weight is as simple as sleeping more, why don’t we do it?

There are three reasons we don’t sleep more:

  1. Social stigma: There is a negative stigma about sleep that permeates every part of our society. If you say you slept for eight hours, you’re seen as kind of a loser. The perception is that sleeping means you are lazy, so people say they sleep less than they do. Very few people admit to getting eight hours of sleep. This social stigma is a cultural problem and we have to change that attitude.
  2. Our 24-hour society: In the past, when it was dark and there wasn’t much to do, we went to sleep. We had few other choices. Today, we have artificial light and an unending list of things to do.
  3. Lack of knowledge: People don’t know as much about sleep as they do about other areas of health. There has recently been much more interest in sleep, but still there is a large gap between what educated and uneducated populations know about the topic.

How much sleep do you get?

I get eight hours. And, I nap. I try to go home for lunch and take a nap, and yet I’m also very productive.   Contrary to popular thinking, it’s bad to work tired. It’s not a good idea to sacrifice sleep. 

How would you extend this thinking to the broader Stanford community?

Most people at Stanford take time for exercise because they understand the benefits (including a better mood or increase in energy). The same thing should be true for sleep: we have to make sure we don’t burn the candle at both ends. Sleeping brings creativity, productivity and the ability to perform at a higher level.

Are there individual differences regarding sleep duration and patterns?

There are many individual differences when it comes to sleep. We take people and suddenly put them on five hours of sleep and some people are devastated, while some people actually function well. And when you repeat that schedule, the same people function poorly and the same people function well.

Ah, like multitasking! … Do most people insist they “do fine” with less sleep?

Yes! [laughter]. But people are not skilled at measuring how tired they are! Many people think they are fine, but are they are not. When subjective and objective sleep studies are done, people are asked how tired they are versus measuring their performance or how fast they fall asleep in a dark room. And their responses don’t correlate very well with the real outcomes! 

People say they’re fine, but their performance can be terrible. People don’t have a good idea of how tired they are, yet still they go on to do all kinds of jobs such as drive trucks or perform surgery.

What has surprised you most over the course of your career?

Every time you look, there's a connection to sleep. Anything you look at in society — from driving to neurology, productivity to prostate problems — is impacted by sleep. I suppose that shouldn’t be surprising considering we spend one third of our life doing it, but it means my job is deciding what not to study.

… any final thoughts?

Much happens during sleep. We have to make sleep important. Sleep is something we have to respect. There are three pillars of health: nutrition, exercise and sleep. Exercise and nutrition already get a lot of attention. I’d like people to consider sleep as important as exercise and nutrition, and give sleep the same level of attention.

Interview conducted by Julie Croteau and edited by Lane McKenna Ryan.

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