It makes us happier, more positive, gives us a better mental attitude. Exercise increases our intake of oxygen, which is good for our physical well-being and good for our brain, we think better and clearer. In studies at New York City's Baruch College, exercise psychologist Joan Gondola found that college students who ran regularly or took aerobic dance classes scored significantly higher on a standard psychological test of creativity than students who hadn't exercised. Exercise also triggers the release of several key neurotransmitters, including epinephrine and norepinephrine, that are known to boost alertness. It's necessary to exercise to lose weight, at least, to do so in a healthy way.
Aerobic exercise burns up calories.
Anerobic exercise such as weightlifting increases the amount of muscle we have and muscle burns up more calories than non-muscle. Also, exercise really increases our metabolic rate, which is the rate of burning calories. Exercise simply makes us feel better. It invigorates us. It gives us a health-conscious attitude.