@SaltedPretzel
I echo what the other posters are saying 'ask him flat out why he keeps commenting on your food!'
Don't expect him to stop though. Some people are so thick and arrogant and obtuse, that even when confronted with their (shitty) behaviour, they don't change it.
YANBU at ALL. I hate it with a PASSION when people mention what I am eating. I get co-workers doing it occasionally, and even random strangers when I am eating a banana on a park bench! DH does it too sometimes. Not maliciously at all, and maybe just making conversation, but it irksome. Especially as I have suffered from an eating disorder my whole life, so I am conscious of people watching me eat. (and I am expecting a comment!)
DH doesn't say things TOO often, but when he does, he will (for example) say (when I come into the lounge with a bag of wotsits,) 'you like your wotsits dontcha?' with a sly squinty-eyed look. Or 'another custard cream!' when I have had 2 and gone back for one more. I just sigh and try and enjoy eating them.
He got annoying a while back, commenting on everything I ate, because he was on a very strict diet. Liquid and fruit only. It got to the point where I was taking a kitkat or pack of quavers or wotsits and going into the garage to eat it, or going for a walk and eating it, because I got sick of the comments.
Also comments from people like 'you'll get fat eating that,' and 'how many maltesers can one girl eat?' pisses me off. Fuck off commenting about my food and my eating. 
I went for a meal out with 3 colleagues a few years ago, and one of them (who seemed to be on a diet 90% of her life, and had a salad for her main meal,) commented on my meal ELEVEN times when I was eating. 'Bloody hell, look at the size of that pie!' 'Where you gonna put all THAT food?' 'I can't believe you're gonna eat all that' and 'apple crumble and custard? Must be a thousand calories in that.'
Literally, a constant barrage of comments. By the 7th or 8th one, one of the other women said 'jeez Carol, you're a bit obsessed with what Poppy's eating aren't ya?' Carol said nothing, and then made 3 or 4 more comments. I rolled my eyes and said 'Carol, just get some food instead of a bowl of lettuce if you want, take your mind off what I am eating.'
She said 'I could never eat as much as you.' 
I never ever ever went out with my colleagues for a meal again, when SHE was going. I paid £35 for my meal out that night, and it was ruined by her commenting.
Weirdly, she didn't make any comments about anyone else's meal, and I didn't have anymore than anyone else.