Bobo you are underweight and have an unhealthy attitude to weight and food.
I am overweight and also have an unhealthy attitude to food but I am capable of understanding what is healthy.
Op looks and is healthy and not overweight to my eye she may perhaps be a little overweight according to bmi which is now being deeply criticised in many medical areas. As much for the fact there are people a supposedly healthy weight but who carry their weight in unhealthy areas of the body and have more body fat, higher unhealthy cholesterol levels etc than someone else who is bmi overweight.
Food is my vice, I'm heavy at the moment but as every year will likely lose about a stone in the summer. I am veggie, barely drink, don't smoke or take Street drugs. I'm on medication which increases appetite and have a mobility issue which restricts exercise I can do I can't even swim at the moment (which I'm really missing). BUT my cholesterol, blood pressure, blood sugars etc are all healthy. My gp even says the only reason health wise for me to lose weight is to help the mobility (but even there it wouldn't make much difference)
My ex was/is like this. I was a size 6 when we met, the criticism began when I hit a size 8! By the time we split (he was cheating) it was constant and nasty including a nickname he called me in public! I was a size 10 by this point. We split, I lost a load of weight due to the stress, then I gained A LOT! By the time he got engaged to ow I was a size 16, guess who came crawling around? She was a size 8 when the got together, after 2 babies she was a size 10 and going to WW as he'd convinced her she was FAT! she only just qualified to go!
In my ex's case it's a sort of vanity, he is all about appearances, he was slim and fit himself usually (though developing a paunch and balding now!), but he valued himself on what others saw of his outward appearance stuff, what brand clothes he was wearing, his car, watch, phone...this extended to his wives being attractive (he was weirdly pleased when I went for a job interview at his place and his boss commented on my attractiveness). One of his most used and hurtful comments was 'I'm ashamed to be seen with you'.
My advice would be to leave or at least give a genuine ultimatum 'stop or I'll leave!'. But I don't think you will. So...every time he criticises you bring his attention to it but in an organised way, keep a tally, return the favour, at the very least say 'that hurt my feelings'.
There's a quote in pretty woman that psychologists know to be true 'the bad stuff is easier to believe'
Oprah did an experiment on her audience years ago (the subject I think was emotional/verbal abuse of children) where she had plants in the audience saying lots of comments they could smell something really stinky. Then Oprah did something like apologise (the audience thinking they weren't filming yet) for a drain problem or something, hands up who smelt it - and loads of the audience said they smelt it, also footage of them saying they could smell it as they queued. Then Oprah made the point if you're told every day, several times a day, by someone supposed to love you, that you're ugly/fat/stupid/cruel/evil etc eventually you believe it, cos why would they say it all the time?