Explain why extended exercise is considered to be "healthy"

Many physical disorders that occur in humans are attributed to the styles of living and general eating habits. Conditions such as diabetes, depression, dymentia and even some cancers are led by bad eating habits. A friend once asked me: Now that I do not want to become obesse but want to be muscular, what will I do since I have to gain mass but I don't want to overfeed? My answer was so simple. EXERCISE
Exercise can be in many forms. The most common modes of exercise are gym and athletics. If you don't do regular exercise, your body does not find a chance to get rid of the many wastes produced by different metabolic processes. Some of these products are toxic and they lead to bad effects in the body. The effect is getting lifestyle diseases.
Exercise plays a key role in boosting your memory. During and after exercise, blood becomes more oxygenated and the supply of oxygenated blood to the brain is increased. This ensures there is renewed strength in the brain parts e.g. hypothalamous and hence boosting thinking ability.
We can not overlook the fact that exercise is fun. When exercising, you are happy and happiness makes you stay healthy.

They must use the scientific method