We’ve all experienced those nights where we toss and turn all night and waking feeling like we didn’t get any sleep at all. The occasional night like this is an inconvenience, and will often lead us to eat more, drink more caffeine, and perhaps skip our workout that day. Provided we get to bed early that night and get back into a pattern of good sleep, it’s not a problem.
However, when we experience this night after night, or find ourselves staying up later in the hopes of tiring ourselves out so we can fall asleep more easily, we start to suffer from sleep deprivation.
Why does sleep matter?
Sleep gives our bodies a chance to rest, restore, and repair damaged cells. Overtime, inadequate sleep starts to impact our physical and mental health, weakening our immune system, making it more difficult to feel happy and make healthy choices, and we often try to use food and stimulants to power through. Chronic sleep problems disrupt this rest and repair cycle, making it almost impossible for our body to repair itself properly.
How does disrupted sleep contribute to weight gain?
The disruption of sleep leads to increased appetite as the body seeks fuel, in particular calorie dense foods such as those with carbs and sugar. Foods rich in carbs and sugar can lead to more sugar in your system, causing spikes of insulin to bring the sugar levels down. Over time this process leads to fat gain and insulin resistance as the body finds a way to store the excess sugar. All of this plays into how well your body metabolizes fuel, and thus, your weight.
Studies have shown that not only does sleep deprivation cause you to put on weight due to insulin resistance, but it also causes the body to slow down metabolism. In fact, a review of studies testing this found that, “Laboratory studies have clearly shown that sleep deprivation can alter the glucose metabolism and hormones involved in regulating metabolism, that is, decreased leptin levels and increased ghrelin levels.” Leptin is the hormone that makes you feel full, while ghrelin it the hormone that makes you feel hungry.
Why does the body slow the metabolism down?
To understand why this happens, you need to understand what the affected hormones are doing. The hormones are: cortisol, ghrelin, and leptin.
Cortisol: is the stress hormone that keeps the body in fight or flight mode when we’re anxious and stressed. Most people experience increased stress levels and increased cortisol levels when they haven’t had sufficient sleep. This increased stress increases our cravings for sugar and carbs - high energy foods that will allow us to escape a situation. Of course, if we can’t escape the stressful situation, this additional energy doesn’t have anywhere to go. Unfortunately, our bodies don’t let go of unused energy - it stores it as fat.
Ghrelin: this aptly named, as you can think of it as the gremlin in your stomach that begs for food - it’s the hormone that makes you feel hungry. When we’re tired from lack of sleep, our levels of ghrelin increase as, again, our body desires more fuel to keep going and supply the body with energy. This is why we often desire to snack all day long after a bad night's sleep or when we’ve had little sleep.
Leptin: Leptin is the hormone that’s released when our stomachs are full; it sends signals to the brain letting it know that we’re satiated. As the levels of cortisol and ghrelin increase, leptin levels fall, meaning not only do we want more food, but we’re less likely to feel full.
Why our metabolism slows down isn’t totally clear, but it’s thought to happen as a response by the body to try and ensure your body has more than enough fuel to keep going no matter what happens.
How do we combat a slower metabolism and thus weight gain?
Getting more sleep and practicing good sleep hygiene is the only way to fight the damage sleep deprivation can do to your body. You’ve got to give it ample time to rest and repair itself, or your body will continue in survival mode - your metabolism will continue to be slow and you’ll continue to have sweet cravings. If you are ready to start your weight loss journey learn more here.
Dr. Nancy Rahnama, MD, ABOM, ABIM, is a medical doctor board certified by both the American Board of Obesity Medicine and the American Board of Internal Medicine. Her specialty is Clinical Nutrition, that is, the use of nutrition by a medical doctor to diagnose and treat disease. Dr. Rahnama has helped thousands of people achieve their goals of weight loss, gut health, improved mood and sleep, and managing chronic disease.