I started yo-yo dieting when I was 14 years old, and by age 18 I thought I knew everything there was to know about diet and exercise. I followed rules like Avoid junk food and exercise as much as you can. Despite sticking to these "rules," I couldn't seem to lose the extra 40 pounds on my body. Not only could I not lose it, I simply wasn't making any weight-loss progress at all.
I thought the answer was a lot of exercise. So I religiously participated in intense classes, from spin to kickboxing to ice hockey — in the hopes that I would burn more fat. Instead, what happened was that I got stronger and had more stamina, but my body size was getting bigger.