The majority of weight loss advice can be distilled down to these two pieces of advice: Eat less, exercise more. While both are important, we often forget about the third crucial pillar that affects our weight: sleep.
In today’s time-starved world, getting enough sleep rarely makes the top of any list, much less one related to our weight loss goals. An impressive—and conclusive—body of research shows that sleep may be the missing component in many people’s fitness and dietary regimes.
Sleep has a surprising impact on what we eat and how much, the fat we have and where we store it, and the amount of muscle we have and can continue to build. Here’s a breakdown of the compelling (and sometimes surprising) reasons that getting adequate sleep is essential for both achieving and maintaining a healthy weight.
Sleep Impacts Hormones That Help Us Eat and Exercise
1. Leptin and Ghrelin
Sleep affects several hormones in your body that directly relate to weight gain and loss—most importantly, leptin and ghrelin. Leptin (produced by your body’s fat cells) suppresses hunger; ghrelin (released by your stomach) increases it. Lack of sleep not only lowers your leptin levels, making it harder for you to feel full, it also raises your ghrelin levels—making you feel hungrier, especially for foods high in carbohydrates. When you are well rested, you’ll feel less hungry and burn more calories—because your body won’t mistakenly hold onto them—making weight loss much easier to attain.
When we don’t get enough sleep, our bodies produce more cortisol—commonly known as the stress hormone. High cortisol levels lower your metabolism, impair your body’s ability to build muscle mass, and cause your body to break down protein into glucose (sugar). Any excess glucose is then stored as—you guessed it—fat. High cortisol levels are specifically linked to visceral (belly) fat, often the most stubborn fat on the body. Consistently high cortisol levels also leave us vulnerable to insulin resistance, a precursor to both diabetes and obesity.
3. Growth Hormone
During sleep, our bodies release growth hormones that help our cells regenerate, reproduce and grow. This is essential for any exercise regimen to work correctly, from running and biking to weightlifting and yoga. Exercising creates microscopic tears in your muscle tissue, and getting adequate sleep provides your body with the hormones it needs for muscle repair and growth.
Sleep Improves Athletic Performance
Exercising makes sense for weight loss; as you work up a sweat, you can almost visualize yourself burning those calories away. It’s harder to feel the immediate impact of getting enough rest, but it’s just as important to making sure your exercise makes a real difference.
When you’re tired, you can’t put forth as much energy in your workout—you’ll burn fewer calories and build less muscle, even though it feels like you’re working just as hard. Conversely, when you are fully rested, you’re able to work harder and longer, leading to muscle growth and a higher metabolic rate.
Adequate sleep also boosts your performance for tasks that require intense focus and cognitive function, like reaction time and hand-eye coordination—perfect for anyone who prefers to exercise by playing a sport.
Sleep Boosts Your Impulse Control
One study from Columbia University and St. Luke’s-Roosevelt Hospital Center found that people who are tired show increased activation in the insular cortex—the region of the brain that regulates pleasure-seeking behaviors. When you’re poorly rested, you’re more likely to seek immediate gratification. Where can you find that instant “feel good” fix? The study shows that most people turn to food.
The researchers found that unhealthy food activated that region more than healthy food. Being poorly rested makes us more susceptible to junk food cravings (this is on top of the fact that our leptin and ghrelin levels already make us feel hungrier in general).
Sleep Schedules Correlate to Body Fat Percentage
According to a new study published in the American Journal of Health Promotion, the amount of sleep we get each night and when we sleep can impact how much fat we have on our bodies. The study tracked 300 female college students aged 19 to 26, and found that women who followed a regular sleep routine (to within 60 minutes or less) had a lower percentage of body fat than those whose sleep hours varied by 90 minutes; the greater the variation in sleep, the greater the difference in body fat.
The women who woke up at the same time every morning (including weekends) showed the lowest body fat, as did the women who slept more overall—between 8 and 8.5 hours a night.
Researchers are still unsure exactly why our sleep schedules impact body fat; but these findings correlate with other studies that suggest we burn more calories, lose fat more easily, and are less likely to reach for a late-night snack when we’re well rested. That’s not to mention the fact that we also burn calories while sleeping—a solid argument for sleeping in if we’ve ever heard one!
Sometimes, Less is More
It’s tempting to think that if we aren’t seeing the fitness results we want, we need to do more—more running on the treadmill, more meal planning, more yoga. Our society even praises the concept of sleeping less in order to do more, evidenced by popular sayings such as “I’ll sleep when I’m dead” and the latest “yolo” (you only live once!). The truth is, sometimes you need to do less in order to accomplish more.
You can put all your efforts into exercising regularly, cooking healthy meals and working hard towards maintaining a healthy weight; but if you don’t ever pause to rest, your endeavors will be in vain. The research showing how sleep affects our hormones, appetite, and athletic performance makes a compelling case for making more time in our busy lives for adequate sleep. When it comes to losing and maintaining weight, taking it easy can truly be more beneficial than pushing ourselves to the limit.
If you’re already following a healthy diet and exercise routine, and you’re still not seeing the weight results you want, considering doing a bit less. Make it a priority to get adequate sleep each night, on a consistent schedule, to give your body the support it needs to succeed.
About The Author: Cortney Berling is a registered dietitian nutritionist at Tri-City Medical Center, a full-service, acute-care hospital located in Oceanside, California. She received her Bachelor of Science in Dietetics at The University of Cincinnati and completed her dietetic internship at The Cleveland Clinic.