Regular poster. NCd.
My DP was staying here this weekend (Friday to Sunday). Been together 6 months. I am a few stone overweight, he is skinny.
On Friday he noticed an old weight loss certificate on my fridge and we had a chat about it and I said that it was old and that I'd fallen off the wagon and was planning on going back to the class when I got more time in a couple of weeks. Last night, after my DCs were in bed, we were having a conversation about running/jogging as both of us have lapsed and want to re-motivate ourselves. He asked me if my medication (ADs for previous anxiety and asthma meds) had made me put weight on, I said I wasn't sure. Then he said "What happened? Did you have one cream cake too many one day and just keep going?"
Ouch. 
He hit a raw nerve. I got upset. I told him that I thought it was a really shitty thing to say to anyone, never mind someone you're in a relationship with and that I was very hurt. He said he was very sorry, acknowledged that he couldn't take it back and said that he was going to pack his stuff and go home.
Before he left, I asked him what he was thinking/feeling and he said "bad".
Last night I was so upset I felt like this was the end of us. His comment suggested that I am not perfect for him the way I am now and that's not good enough. However he has never said anything to suggest this before, never mentioned my weight before etc.
My STBXH has ASD and often said hurtful comments so I am finding it hard to see this situation objectively. How bad was his comment?