This article (out of Northwestern University in Chicago) reviews the most effective lifestyle changes and their effect on the Metabolic Syndrome.

Recent article that will probably convince you to make up your own mind (and not depend on official government recommendations) about what is best for your health.

Good research showing that 30 to 60 minutes of walking per day is enough to maintain normal weight in most overweight people.  But, notice that this means every day (or making up for lost by walking or jogging more the next day).   In the costal area where I live, if hot weather or rain keeps you from exercising then you're probably not going to lose weight and keep it off because it's either hot or raining most of the time.