I had to lay down the "I don't need a food monitor" law in my house too. My husband would do this too! And he fully admitted I wasn't overweight (I wasn't) and that even if I was, it would be out of line for him to mention it, but for some reason, he would say things like, "Didn't you just eat?" or "What are you eating now?" type things....
I kept it light at first like, "Hey, dude, just fyi, I have been a health and fitness fanatic pretty much my whole life, I absolutely know what to eat, and you really don't need to keep track of it for me" Then, he'd agree, but then he'd do it AGAIN and AGAIN. To be honest, he still does it sometimes and I yell "FOOD MONITOR,NO!!!!" It's like a nervous tick with him or something.
But he's one of those types to NEVER changes little annoying habits no matter how many times you ask...so. I feel your pain. For the record, my husband is no exercise buff and could stand to lose a few pounds and I WOULD NEVER HASSLE him about it. I's a personality thing. Annoying.
Hopefully if you just TELL your husband not to do that, he'll quit.