My fiancé doesn’t support me wanting to lose weight

So my fiancé has a weird feeding/weight gain fetish. I didn’t know about it until 5 years into our relationship, some weight gain from me. and after accidentally stumbling across some porn he was watching… which was morbidly obese women stuffing their faces with food.. it’s gross to me, but whatever tickles his fancy I guess.

Lately I’ve been wanting to get healthier and lose weight, I’ve been feeling horrible with myself and not being able to keep up with my 4 yr old. I wish I was able to run around with him more without running out of breath so fast.

I told my fiancé this. I Started drinking more water. Eating Less junk food. Drinking Less soft drink. And the next day he came home from work with a huge bag of chocolates and junk food for me. I want to LOSE weight. How the hell do I stay committed to that when he won’t support me or help me.