You never grow muscle in the gym that happens when you rest and sleep, no point going to the gym busting your ass following with a few hours sleep, should get at least eight hour per night, your first four is to repair the damage you caused, the other four is to recover. I have found 18 other reasons for getting a good night sleep.

1. Impaired glucose tolerance.

Without sleep, the central nervous system becomes more active, something that inhibits the pancreas from producing adequate insulin, the hormone the body needs to digest glucose. "In healthy young men with no risk factor, in one week, we had them in a pre-diabetic state," says researcher Van Cauter when referring to a study that he conducted on the effects of sleep deprivation.

2. Possible link to obesity.

Growth hormone (GH) is secreted during the first round of deep sleep. As both men and women age, they naturally spend less time in deep sleep, which lowers GH secretion. Lack of sleep at a younger age, however, could drive down GH prematurely, accelerating as a result the fat-gaining process. In addition, there is also research that indicates a lowering of the hormone testosterone as well, something that would also make the gaining of fat and the loss of muscle and easy thing for the body to do.

3. Increased carbohydrate cravings.

This is due to the fact that sleep deprivation negatively affects the production of a hormone called Leptin. This hormone is responsible for telling the body when it is full. However, with decreased production of this hormone, your body will crave calories (especially in the forms of carbs) even though its requirements have been met. Not a good situation to be in for a dieter.

4. Weakened immune system.

Research indicates that sleep deprivation affects adversely the white blood cell count in humans as well as the body’s ability to fight infections.

5. Increased risk of getting breast cancer.

Richard Stevens, a cancer researcher at the University of Connecticut, has speculated that there might be a connection between breast cancer and hormone cycles disrupted by late-night light. Melatonin, primarily secreted at night, may trigger a reduction in the body's production of estrogen. But light interferes with melatonin release (since melatonin is secreted in response to a lack of light), allowing estrogen levels to rise. Too much estrogen is known to promote the growth of breast cancers.

6. Decreased alertness and ability to focus.

A recent study showed that people who were awake for up to 19 hours scored worse on performance tests and alertness scales than those with a blood-alcohol level of .08 percent–legally drunk in some states. Also, this can lead to injury in the weight room since lack of alertness can cause you to neglect securing a machine correctly or even lose balance as you perform an exercise.

7. Hardening of the arteries.

Stress imposed on the body due to lack of sleep causes such a very sharp rise in cortisol levels. Such an imbalance can lead to hardening of the arteries, something that can cause a heart attack. In addition, we also know that very high cortisol levels lead to muscle loss, increased fat storage, loss of bone mass, cause depression, cause hypertension, cause insulin resistance (the cells in the body lose the ability to accept insulin), and lower growth hormone and testosterone production.

8. Depression and irritability.

Lack of sleep also causes depletion of neurotransmitters in the brain that are in charge of regulating mood. Because of this, sleep deprived people have a “shorter fuse” and also tend to get depressed more easily

9. Keeps Your Heart Healthy

Heart attacks and strokes are more common during the early morning hours. This fact may be explained by the way sleep interacts with the blood vessels. Lack of sleep has been associated with worsening of blood pressure and cholesterol, all risk factors for heart disease and stroke. Your heart will be healthier if you get between 7 and 9 hours of sleep each night.

10. May Prevent Cancer

People working the late shift have a higher risk for breast and colon cancer. Researchers believe this link is caused by differing levels of melatonin in people who are exposed to light at night. Light exposure reduces the level of melatonin, a hormone that both makes us sleepy and is thought to protect against cancer. Melatonin appears to suppress the growth of tumors. Be sure that your bedroom is dark to help your body produce the melatonin it needs.

11. Reduces Stress

When your body is sleep deficient, it goes into a state of stress. The body's functions are put on high alert which causes an increase in blood pressure and a production of stress hormones. Higher blood pressure increases your risk for heart attacks and strokes. The stress hormones also, unfortunately, make it harder for you to sleep. Learn relaxation techniques to counter the effects of stress. There are also stress reduction techniques for sleep.

12. Reduces Inflammation

The increase in stress hormones raises the level of inflammation in your body, also creating more risk for heart-related conditions, as well as cancer and diabetes. Inflammation is thought to one of the causes of the deterioration of your body as you age.

13. Makes You More Alert

Of course, a good night's sleep makes you feel energized and alert the next day. Being engaged and active not only feels great, it increases your chances for another good night's sleep. When you wake up feeling refreshed, use that energy to get out into the daylight, do active things, and be engaged in your world. You'll sleep better the next night and increase your daily energy level.

14. Bolsters Your Memory

Researchers do not fully understand why we sleep and dream, but a process called memory consolidation occurs during sleep. While your body may be resting, your brain is busy processing your day, making connections between events, sensory input, feelings and memories. Your dreams and deep sleep are an important time for your brain to make memories and links. Getting more quality sleep will help you remember and process things better.

15. May Help You Lose Weight

Researchers have also found that people who sleep less than seven hours per night are more likely to be overweight or obese. It is thought that the lack of sleep impacts the balance of hormones in the body that affect appetite. The hormones ghrelin and leptin, important for the regulation of appetite, have been found to be disrupted by lack of sleep. So if you are interested in controlling or losing weight, don't forget to pay attention to getting a good night's sleep.

16. Naps Make You Smarter

Napping during the day is not only an effective and refreshing alternative to caffeine, it can also protect your health and make you more productive. A study of 24,000 Greek adults showed that people who napped several times a week had a lower risk for dying from heart disease. People who nap at work have much lower levels of stress. Napping also improves memory, cognitive function and mood.

17. Reduce Your Risk for Depression

Sleep impacts many of the chemicals in your body, including serotonin. People with a deficiency in serotonin are more likely to suffer from depression. You can help to prevent depression by making sure you are getting the right amount of sleep, between 7 and 9 hours each night.

18. Helps the Body Make Repairs

Sleep is a time for your body to repair damage caused by stress, ultraviolet rays and other harmful exposures. Your cells produce more protein while you are sleeping. These protein molecules form the building blocks for cells, allowing them to repair damage.