That is not bad advice
You want to listen to your body because it tells you way more things than just feeling hungry. That is a gross simplification of that suggestion, almost assuming human bodies are machines.
Bad advice in this context is saying “you are gonna be happier if you lost weight” or “you are gonna look better if you lost weight”. That is extremely personal and changes person to person, some might even feel worse.
Listening to a doctor’s concerns is for everyone with no exclusions, but feeling good in oneself’s body is another different topic that needs to be tackled appropriately.
I really like this answer! Absolutely gorgeous response. Confidence is massively important for being happy with oneself, and that starts by understanding you are a singular original human.