I'm 62 heavy. Do my intervals on treadmill, walk. Warm up, then do from 1 to 2 min at fast pace and raise the platform, then I slow down until heart slows to a certa Built in heart monitor. I noticed improvement immediately, not in weight but in how I feel. Could push it more on the next session. When I go to the weight room, everything feels better. Rest intervals between sets are less. I am a firm believer. Even at my age my muscles and heart respond to being pushed, feels great. Exercise and southbeach diet are seeing results in pounds and inches. SB diet specially good for belly fat and is heart healthy.