Sleep More, Weigh Less?

Aaron B. Holley, MD


May 10, 2022

During my residency more than 20 years ago, I was sleep deprived and gained a lot of weight. After rounding in the hospital well past midnight on a Sunday, I shuffled slowly into the breakroom between the surgical and medical ICUs. A large tub of fried chicken sat unattended on the table, no doubt purchased by a well-meaning member of the night team trying to support their shift-worker colleagues. They hadn't accounted for me, the overworked, sleep-deprived third-year medical resident struggling through the backstretch of a 36-hour marathon call.

The more basic areas of my brain leapt into action. The precious effort required for higher-order cortical processing couldn't be wasted or simply wasn't possible at that point in the night. This would be a System 1 decision. In a flash, I bellied up to the table. A breast and two drumsticks vanished faster than a post-call psychiatry intern working the ICU. I quickly fled the area and beat a shameful retreat to my call room to wallow in a sweat of grease and guilt.

Maybe my leptin and ghrelin levels were off. Perhaps my brain mistook sleep deprivation for a caloric deficit, and I was "eating to stay awake." Maybe fatigue had eliminated my willpower and I fell prey to hedonistic behavior. Whatever the reason, I ate that chicken without pausing to consider whether I was hungry. That moment was emblematic of my entire residency. The synergy of sleep deprivation, fatigue, and unhealthy eating led to a 20-lb (give or take 5 lb) weight gain.

It wasn't until my sleep fellowship many years later that I realized that sleep might be related to weight. In observational studies, as self-reported sleep decreases, the likelihood of weight gain and obesity increases. The onset of our current obesity epidemic is mirrored by a reduction in total sleep time per night at the population level.

Many erroneously assume that because sleep is associated with inactivity and a lower metabolic rate, too much and too little lead to weight gain and loss, respectively. This widespread misconception is only half correct. Humans burn fewer calories during sleep compared with wake. However, weight gain is a product of calories ingested minus calories expended. When we're sleep-deprived, we overcompensate for the calories we burn while awake — meaning, we eat too much. We also shift the macronutrient content of our food and eat more carbohydrates. The net result? Weight gain.

There's a proposed evolutionary explanation for the relationship between sleep and eating. It turns out that when we restrict our caloric intake, the percentage of time spent in slow wave sleep (SWS) increases. Our metabolic rate nadirs during SWS. In short, when there's not enough food around, our body tries to reduce energy expenditure. We basically hibernate to prevent starvation, thus giving rise to sleep's relationship to energy intake.

Given these physiologic realities, can increasing total sleep time (TST) lead to weight loss? A new study, published in JAMA Internal Medicine, randomly assigned younger, overweight (body mass index of 25-29) adults who sleep less than 6.5 hours per night into two groups. The first was counseled to increase their TST to 8.5 hours per night and the second received no specific instructions for sleep. There were no further interventions nor specific goals for diet and exercise. Participants were allowed to continue their normal routine, and caloric intake wasn't controlled.

The investigators found that 2 weeks of sleep extension was associated with a 0.87 kg weight loss and a drop in caloric intake of 270 kcal per day. The control group had small increases in weight and intake. If you've ever uttered the cliché phrase "there' no such thing as a free lunch," this study makes you sound foolish. If I'm not mistaken, the authors just proved that sleep alone has an impressive effect on metabolism.

I can't help but marvel at the effect of their intervention. Individualized counseling leading to an increase in TST of 1.2 hours per night? That's amazing! My conversations with patients about increasing sleep typically start with statements of denial. "I don't need that much," or, "So-and-so gets by with 4 hours per night." These comments then give way to incredulity. "How do you expect me to get 8 hours per night? I have a long commute, kids ..."

The above paragraph is garnished with a little hyperbole, but just a pinch. In our fast-paced, 21st century world, finding a spare 1.2 hours per 24-hour day isn't easy. It involves difficult behavior change and tough choices. This reality is born out in epidemiologic studies on TST nationwide that show a growing percentage of the population is restricting their sleep.

Issues with generalizability of the intervention aside, and despite the fact that this was a small, single-center study, the results are critically important. It represents proof of concept. Despite my nihilism, I always spend time advising patients with insufficient TST to get more sleep. The JAMA Internal Medicine paper shows that individualized counseling can have the desired effect, and benefits to physiology and metabolism will follow. Sustained weight loss requires more than just an increase in TST, but sleep optimization is a key component.

Aaron B. Holley, MD, is an associate professor of medicine at Uniformed Services University and program director of pulmonary and critical care medicine at Walter Reed National Military Medical Center. He covers a wide range of topics in pulmonary, critical care, and sleep medicine.

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