Been there, done that. I worked harder at the physical fitness thing than anyone else I know. Intense running (distance and intervals), brutal weight workouts heavy on the power stuff (squats, deadlift, full-body stuff), etc. My doctor told me, I had the cardiovascular system and lung capacity of an Olympic athlete - and he had actually treated them in his practice. Guess what? I still got fat.
Worse yet -- even if all that exercise had worked, back then, I can't do it any more due to a lifetime accumulation of injuries. Running twice a week is all I can handle now, without injury flareups. Thank God, lowcarb DOES work, even with my forcibly reduced exercise schedule.