Everyone Getting Fat on Normal Diet + BMI Setting Suggestion

For some reason or another everyone seems to be getting obese the longer the game runs, not just those in the household, and dieting just makes them get too thin because I can't just leave it on normal to maintain. I feel it'd be better instead of just having the cook manage BMI that it might be best to have it an option in Talk for each character to maintain -- maybe with bonuses once you build the gym. That way they stay within the range and you've set it for that character alone, maybe even adding muscle settings at some point.

Creating exceptions through the cook doesn't solve the problem because they will just get fat again once I put them on a normal diet and those outside of the house shouldn't be controlled by it anyways, I would think.