If you’d like an anecdote…
When I was young, probably around 4 or 5 years old, I collected pictures of models so I could copy certain things about them - their smile, hair, posture, etc. I wasn’t trying to lose weight at that age, but I certainly was aware of social concepts of beauty, and I didn’t even watch that much television compared to most kids.
If you’d like an idea to maybe explore further…
I think children’s programming has a lot to do with the attitudes we develop about body image. The protagonists of cartoons, Disney movies, etc., are generally beautiful and thin or handsome and muscular, while the antagonists are ugly and/or fat. I personally believe that what I watched as a child strongly influenced my perception of beauty.