Interestingly, I can not recall the study, but there was one where they determined that there are several groups of people, who overeat for particular reasons, and who respond more effectively to either diets, or training.
This is the reason why we see so many guys saying - I diet so hard, but nothing changes! Because he is a responder to training, and he would get more benefits by training, rather than by dieting.
Obviously, doing both would improve the fat loss big time for those who respond to both things, but it is very plausible that there are people who respond so much better to training than to dieting.