A few years ago, I went to the doctor because I was having frequent diarrhea. The doctor did all kinds of different tests. I finally figured out that it was the whey protein that was keeping me close to the bathroom.
After 20 years of working out, and trying LOTS of different supplements, I can say that the ONLY thing that works is Creatine. ALL the rest is a waste of money.
1) If you have a thin to average build, eat 5 meals a day and lift heavy weights. You'll gain weight, but it will be muscle weight which is heavier than fat weight.
2) If you're over weight, cut out all the bad foods like sodas, pre-packaged frozen dinners, and anything from a vending machine. Don't starve yourself because it puts your body into survival mode so that it stores the excess fat.
Throw out the cookies, chips, and similar crap that has no food value.
Learn to eat some variation of home cooked meat, vegetable, and potato or rice.
Then, decide on something aerobic that you enjoy doing, and do it. It could be a brisk walk for 30 minutes a day, running, tread mill, anything that will burn off some of the calories that you are taking in.
Eat 5 healthy meals a day and lift heavy weights. Don't stuff yourself. Just eat until you're comfortably full.
Throw away the bathroom scales. You will know if you are losing fat weight and gaining muscle weight.