Dieting alone can result in loose skin.

Combine reasonable dieting (not extreme weight loss binges) with very good hydration and strengthening/toning/muscle building exercises to help alleviate the problem. You can't get rid of the problem totally, but you can mitigate it somewhat. We need aerobic exercise as well, but that doesn't really help with loose skin. There is also skin reduction surgery for those that lose a ton of weight. But that is so extreme, and dangerous, I'd stay far clear of it.