The debate about the best way to achieve a healthy weight always revolves around eating and movement. If you want to look better, the most common suggestion is “eat less and move more.” But it’s not that simple, or even accurate. Sometimes you want to eat less and move more, but it seems impossible to do so. And there might be a good reason: Between living your life, working, and exercising, you’re forgetting to sleep enough. Or maybe, more importantly, you don’t realize that sleep is the key to being rewarded for your diet and fitness efforts. According to the Centers for Disease Control and Prevention, more than 35 percent of people are sleep deprived. And when you consider that the statistic for obesity is nearly identical, it’s easy to connect the dots and discover that the connection is not a coincidence.
Think about the last time you had a bad night of sleep. How did you feel when you woke up? Exhausted. Dazed. Confused. Maybe even a little grumpy? It’s not just your brain and body that feel that way—your fat cells do too. When your body is sleep deprived, it suffers from “metabolic grogginess.” Within just four days of sleep deprivation, your body’s ability to properly use insulin (the master storage hormone) becomes completely disrupted. In fact, the University of Chicago researchers found that insulin sensitivity dropped by more than 30 percent.
You produce most of your growth hormone when you sleep. Growth hormone (GH) is aptly named because it is essential for you to grow. But its benefits aren’t limited to bigger and stronger biceps—GH increases your calcium retention (to help maintain your bone mass), it promotes fat loss, it reduces fat storage, it supports your immune system and it keeps your organs operating smoothly. GH isn’t the only hormone affected by sleep. Ever go to bed hungry? If you have a full night’s sleep, you’ll wake up not hungry. During sleep, the body balances two hunger-controlling hormones—ghrelin and leptin. A study in the journal PLoS Medicine showed a strong correlation between limited sleep, high levels of hunger-inducing Ghrelin, low levels of satisfaction-inducing Leptin and obesity. 
Unfortunately, the impact of poor sleep spreads beyond diet and into your workouts. No matter what your fitness goals are, having some muscle on your body is important. Muscle is the enemy of fat—it helps you burn fat and stay young. But sleep (or lack thereof) is the enemy of muscle. Scientists from Brazil found that sleep debt decreases protein synthesis (your body’s ability to make muscle), causes muscle loss, and can lead to a higher incidence of injuries.
Just as important, lack of sleep makes it harder for your body to recover from exercise by slowing down the production of growth hormone—your natural source of anti-aging and fat burning that also facilitates recovery. This happens in two different ways:
- Poor sleep means less slow-wave sleep, which is when the most growth hormone is released.
- As previously mentioned, a poor night of rest increases the stress hormone cortisol, which slows down the production of growth hormone. That means that the already reduced production of growth hormone due to lack of slow wave sleep is further reduced by more cortisol in your system. It’s a vicious cycle.
So what are optimal sleep levels?
Like nutrition, sleep needs are unique to the individual. For males between the ages of 17-35, the national sleep foundation recommends 7-9 hours. Lifestyle and activity levels play a huge factor—the harder you live, the more sleep you need—so you’ll have to figure out your own personal sweet spot.