Whatever a child says from 8 onwards is so, so heavily influenced by their peers and their culture, possibly more so that any other point in their lives, that I would most definitely keep the ‘in trends’ in mind as they expressed their own growing thoughts.
That is it really, I’d listen and notice, allowing their expression.
But I would not be ‘led by the child’ into any action, any extremes and if they seemed to be getting quite intense then I’d steer them back to ‘well, you’ve plenty of time... just enjoy your childhood, explore... no I don’t think actions of this and this yet... ‘etc.
Most children will go a bit extreme whilst they struggle to find themselves in all of our cultural norms. Going into teenage hood the urge to fit in is totally overwhelming. So I would always, always seek the context for my child’s thoughts.
If my child wanted to eat only protein shakes and body build - well obviously they want to look great and are noticing themselves as attractive objects - then I would acknowledge the wish to be attractive but would rein them in from protein shakes, and too much weight training.
If my child wanted to eat less in order to look great in instagram shots I would be advising healthy eating.
If my child said that they hated their body, I would again be trying to help them not hate any part of themselves, if they have uncomfortable feelings that is OK to express, but not OK to demonise themselves as again, that is extreme thinking no matter what any role model on TV says.
It is OK to express feelings that they might be feeling different, but childhood is a growing, where every child should feel safe and secure enough to have time to explore all their feelings. But extreme action and damaging extreme thoughts are not healthy for a child and are the product of people whipping up hysteria around children.
I believe it is my job as a parent to help them to feel safe enough to journey through this time in the most sensible, secure way possible. As we all know, young kids are not very sensible and are often intense! They’ve got the rest of their adult lives to make proper, adult decisions about themselves. Childhood is their one safe place to grow into that.