Wifestuffer:
My wife gets this a lot. She's literally the most massive person in our entire extended family, and her mom and aunties are always concerned about her constantly growing weight.
She forgives them because they're kind people, care about her, and she's aware most women aren't the size of several women put together. She knows they're trying to be helpful, and they just assume a woman her size is unhappy with it.
So she laughs and waves them off-
"I'm getting so fat, right?"
"I'm going on a diet, I swear!"
"My husband is trying to get me in shape!"
Afterwards-
"I'm soooo hungry, can we stop and get some snacks?"
Some of those ways she brushes off comments seem like they're pretty solid ways to do it (albeit not all of them are exactly truthful lol).
I mean, one of my friends always comments on how he's surprised with how I'm not really fat with all the candy and snacks that I have lying around (I don't eat it all myself and I tend to share it). I figure if he or any of the people in our immediate circle brings it up or comments about me gaining, I could be like, "guess all that junk food is finally catching up to me" lol. I could probably also attribute some of it to picking up my wife's eating habits (she's 380lbs, so it wouldn't necessarily be surprising for me to get fat if I start eating more like she does. Plus, I could make some comments like, "yeah, I gained some weight, guess I'm slacking off a bit now that I'm a married man," and "I'm not too worried, I haven't gotten that big, I'm still smaller than my wife."