Think of your body as a living, breathing machine. Just like any machine, if you run it constantly, it's bound to wear out. It gets overheated, parts start to break. Your body needs rest!
A lack of sleep will always lead to fatigue, illness and weight gain.
During sleep your body is able to repair itself from all the day’s activities. Small muscle tears are able to heal and your hormone levels are adjusted back to normal.
When your body is in sleep mode, more blood is supplied to your muscles. This means more oxygen and nutrients available to start the healing process. Then during the non-REM portion of sleep, the pituitary gland releases a shot of the growth hormone GH. Because more oxygen and nutrients are already at the muscle, the repair and growth happen when the growth hormone signals it to begin.
Of course, when you don’t get enough sleep, not as much of the growth hormone is released, so not as much repair and growth occurs, eventually leading to loss of muscle mass, weight gain and fatigue. Essentially making all your hard work useless, and even detrimental to your goals!
Stress Hormones and Weight Gain
When we don’t get enough sleep our hormones cortisol, ghrelin and leptin get all out of whack.
Cortisol is a hormone released by the adrenal glands when the body is faced with a “fight or flight” situation. It's also commonly known as the stress hormone. Unfortunately, for many of us our normal daily activities involve enough stress to have elevated cortisol levels in our systems. When you aren't getting enough sleep, that cortisol level stays elevated much longer than it should. The effects of an elevated cortisol level over time is weight gain.
Why cortisol results in weight gain is due to what it does in the body. When cortisol is released, it floods the bloodstream with glucose so that the body has enough energy to deal with the stress while at the same time inhibiting the release of insulin. So now the cells are deprived of glucose and cortisol won’t let insulin put back the glucose it took out. The cells signal the brain you are hungry. High levels of cortisol can lead to Type 2 diabetes.
The hormones ghrelin and leptin have opposite effects of each other. Ghrelin, produced in the stomach and pancreas, signals your brain it is time to eat. Leptin is produced in the fat cells and is responsible for telling your body that you are full. When you don’t get enough sleep, ghrelin builds up, but leptin does not. This leaves you hungry all the time. And what do you do when you feel hungry? Eat, which leads to weight gain.
Also when sleep deprived, part of that hungry feeling will be a craving for sugar, fats, salt and refined carbs – all which we know are not good for you and result in water retention and weight gain.
So it is pretty easy to see that if you are not getting enough sleep, your efforts to reach peak physical fitness will be stymied at the least and unachievable at the most. If you're having trouble sleeping, you can check out this great article on setting up your bedroom for a great nights sleep.