Oh it really is difficult. Mine is 9, tall, and thin, but she started on about being fat when she was about 6, it was heartbreaking. Someone at school had said her stomach stuck out, which it just didn't! She's as thin as a reed! AND so what if it did! It was just awful.
Now she is pretty able to see that I am eating fundamentally different stuff to her, but we talk about balance, and how it's important to get a range of things, and healthy strong bodies. They're doing something about sugar and healthy eating at school at the moment so she was refusing orange juice this morning. So then we had a conversation about a small glass being ok, though a whole orange would be better, and why if she'd had sweets or a biscuit/bun for snack then it's fruit for pudding.
And THEN we had a really interesting conversation about what they had to eat in Little House on the Prairie - lots of protein, very little refined carbs, no potatoes, no pasta, no rice etc. And very little in the way of fruit and veg - and how different it is from what we have now.
My mum hasn't been overweight very much really - though she always thought she was. Mostly she 's always been slim to thin. So it's doubly hard that she doesn't really get it because she hasn't been where I am.