What are the benefits of being fit?

Benefits of being fit are both physiological and psychological.  Some of the benefits of being  fit include boosting your metabolism to help burn fat, it can assist in decreasing your risk of heart disease and certain cancers, it helps to stop bone density loss (can help slow osteoporosis), it can help with overcoming depression, increase your confidence levels, boost self esteem, allows more rest on less sleep (quality of sleep is better). 
Overall being fit can improve your quality of life in every aspect, physically, mentally and socially. 

There are countless benefits of being fit. Some include:
 
Stronger muscles and bones
Muscles respond to the stresses brought by exercise via hypertrophy. The muscles develop new muscles in order to meet the extra demand for power. The bones also become sturdier with exercise. Bones become stronger in response to stress that is loaded unto itself by the muscles attached to it. By exercising, the body ensures that the bones are absorbing calcium from the blood.
 
Better coping with stress
Exercise becomes an avenue where a person gets ‘time off’ from the usual stresses that he/she faces daily. Through physical exertion, he/she is able to release the stresses that he/she has accumulated, and he/she also becomes better in handling future stressors. It has also been studied that prolonged exercise can result into a ‘runner’s high’.  This occurs when endorphins, or the body’s natural pain-killers, are released, bringing about a sense of well-being and happiness after a hard day’s workout.
 
More restful sleep
Because of physical exertion, the body will naturally require rest. People who exercise regularly have more restful sleep. 
 
Improved ability to focus
Research has shown that exercise stimulates the secretion of chemicals such as the brain neurotropic factor (BDNF). This stimulates neurons to branch and connect in more ways. More neural connections mean that the brain can learn and focus better. 
 
Improved posture
Proper posture is important in ensuring that the bones and muscles of the body are aligned properly to ensure that they can work efficiently whether during movement or static positions. Good posture also ensures that the bones are in correct alignment and are not unduly stressed. Improper posture can overstress bones such as the spine which can result in back pain and eventual degeneration of the spinal discs. 

There are so many benefits to being fit and exercising regularly!  In addition to the great answers above, it can also reduce the recurrence of some cancers (by up to 50% in some instances), aid in preventing type 2 diabetes and reduce the risk of dementia.

If exercise was a pill, we'd all be demanding it!

The benefits to keeping fit are almost innumerable!

• Reduce risk of diseases, such as diabetes, hypertension, high cholesterol, most cancers.
  
• Weight loss or maintainence of healthy weight.
  
• Maintaining muscle and bone mass, particularly with aging.
  
• Psychological benefits - improved mood, reduced stress, anxiety, depression, improved concentration and focus.
  
• More confidence.
  
• Improved sport performance
  
• Improved posture
  
• Reduce pain (eg back pain)
  
• Improved strength and reduced risk of injury.
  

And many more.

Research indicates that fintess is a better predictor of health and disease than fatness. 

You can read more at http://www.sparkpeople.com/blog/blog.asp?post=which_is_better_fit_and_fat_or_skinny_and_unfit

There are psychological benefits of fitness and exercise for depression.
Studies show that people who exercise regularly benefit with a positive boost in mood and lower rates of depression.What Are the Psychological Benefits of Exercise With Depression?Improved self-esteem is a key psychological benefit of regular physical activity. When you exercise, your body releases endorphins. These endorphins interact with the receptors in your brain that reduce your perception of pain.Endorphins also trigger a positive feeling in the body“runner's high,” and can be accompanied by a positive and energizing outlook on life.Endorphins act as analgesics, which means they diminish the perception of pain. They also act as sedatives. Regular exercise has been proven to:

• Reduce stress
  
• Ward off anxiety and feelings of depression
  
• Boost self-esteem
  
• Improve sleep
  

• It strengthens your heart.
  
• It increases energy levels.
  
• It lowers blood pressure.
  
• It improves muscle tone and strength.
  
• It strengthens and builds bones.
  
• It helps reduce body fat.
  
• It makes you look fit and healthy.
  

Is Exercise a Treatment for Clinical Depression?Research has shown that exercise is an effective but often underused treatment for mild to moderate depression.Are there Types of Exercises That Are Better for Depression?It appears that any form of exercise can help depression. Some examples of moderate exercise include:

• Cycling
  
• Dancing
  
• Gardening
  
• Golf (walking instead of using the cart)
  
• Housework, especially sweeping, mopping, or vacuuming
  
• Jogging at a moderate pace
  
• Low-impact aerobics
  
• Playing tennis
  
• Swimming
  
• Walking
  
• Gardening
  
• Yoga
  

Because strong social support is important for those with depression, joining a group exercise class may be beneficial.

Fitness is synonomous with health. So when you think fit think healthy. 
Building your fitness to a healthy level will have a number of benefits which include: 

- better sleep
- improved moods
- more energy
- decreased pain
- prevention of disease such as obesity and diabetes. 

There are a number of types of fitness such as cardiovascular, muscular strength and flexibility. Overall fitness and improved health will come from working on all areas and combining your training with a healthy eating plan. There are very few health benefits to training whilst eating a diet high in saturated fats and sugars (including high sugar sports drinks).