About having a healthy diet: That's actually a verry good question! I have seen overweight people work-out day after day and never make any progress to reduce their waistlines because they refuse to improve their diets. It's good that they do work out but they just never achieve their goal to look better and have the best health possible.
The author of the Zone diet, Dr. Barry Sears, has stated that about 3/4 of the work is to adopt healthy eating habits and 1/4 is exercise. I have tried it and I believe he is correct. If you eat a healthy diet, you don't have to "kill yourself" working out to be healthy.
I recently saw a photo of about 8 retired high school athletic-coaches and they all looked like they were pregnant. I assume they didn't look like that when they were young and active. The problem is: They obviously never paid any attention to developing healthy eating habits.
As far as exercise: I"m a big believer in walking. Walking (slowly or briskly) is actually very good exercise and you won't likely have to wory about getting knee-replacement surgery when you get older. Stretching exercise is also very important as is working out with hand weights. Sit-ups and deep knee bends can be helpful too. (The only time I run is when I'm out walking and it starts to rain
About pills: If you're young and healthy and you eat a healthy diet you probably don't need to worry about taking any pills. Pills, in my opinion, should only be taken if you have a proven need or deficiency.