Deuterated water studies show that until you reach Olympic levels of training, you burn roughly the same amount of calories per day whether you exercise intense

Deuterated water studies show that until you reach Olympic levels of training, you burn roughly the same amount of calories per day whether you exercise intensely or not. Your body simply shunts the available calories to the systems that need them with the highest priority. This means things like your immune system get shortchanged if you exercise a lot. If you want to lose weight, the only real way is to reduce caloric intake. The saying is "You can't outrun the fork." If you want caloric consumption driven by external means--go swimming. Your body must maintain thermal equilibrium and doing so while immersed in cooler water is probably more calorically expensive than the exercise itself. However, the above caveat applies, your body will simply shunt calories around.