I recently finished the 10 week intense exercise program called Insanity. I loved it! I felt great and def got a lot stronger. After 10 weeks I had GAINED 5 lbs!!! What??? And no it wasn’t muscle weight. I was totally discouraged. Since, I have learned of some likely causes of this phenomenon. This article explains 3 of them. It was written about runners but applies to all exercise. I fall under #3!