I'm 6'3" and got about 10lbs on him. But am I fat? Hell no. I think she was being a bit shallow in this case. They were both normal weight when they started. She went to basically model status thin. He didn't. But she still has every right to be with who she wants. She wanted to go deep into the fitness lifestyle and he didn't. That seemed to be an irreconcilable difference.  I can understand his negativity too. I would probably have a hard time dealing with my girl losing a bunch of weight, getting hit on by more dudes, and then eventually dumping me. If he meant enough to her, he would have joined her on this journey and became shredded or whatever, but we all decide our priorities in life.  I would fault her a lot more if they were married, since he was never close to overweight (about 200lbs at 6'3"). But when your just dating, you can leave for any reason you want. If you're not happy with your partner, why waste the time? It is better for both to move on.