Over the past two years, I went from being 1 lbs overweight according to my doctor to 6'1" 175 by gradually starting to run and then then do yoga. I was getting up to six times a week either running 30 mins or 1 - 1.25 hours of yoga, but I hit a limit because of my diet. I just don't eat enough of the right stuff to keep that up and those are moderate (not light) exercises. If I eat sugar and breads it might be technically enough calories, but without the energy to really work out well. I wonder how many people can't get into regular exercise because they don't eat right stuff either.