The Surgeon General reports that if Americans would become active for 30 minutes a day it would improve their health. The report further states that physical activity reduces the risk of coronary heart disease, hypertension, colon cancer, diabetes mellitus, and also improves mental health.
You do not have to greatly change your lifestyle to become more active. Try and think of ways you could become more active in everyday life. Can you walk instead of driving the car? Start a garden this year? Walk the dog of an evening? Vary your activites so you do not become bored. Just be sure that all the activites total up to 30 minutes or more.
The links on this page will deal with specific ways to exercise. Walking, biking, and strength training are my favorite activities. Try and think of exercise that gives you pleasure. Then do it. It may be an uphill road, but you can do it.
Ballroom Dancing
Canoeing (slowly) 180-200 calories
Cooking 185-200 calories
Walking Slowly (2 1/2mph) 210-230 calories
Cleaning 235-355 calories
Brisk Walking (4 mph) 250-345 calories
Golf 300-350 calories
Cycling (9 mph) 315-480 calories
Aerobic Dancing 480-625 calories
Swimming 480-625 calories 
125-310 calories
