DD is 9 yo and weighs around 5 stone and is 118cm tall. She is overweight. Her dad has her EOW, once a week midweek and half of holidays. DD is very greedy; if there's food around, she'll eat it. I've discussed it with my exH before after she's come home talking of having eaten an entire family bag of doritos/malteasers. He thinks she's fine and tells her repeatedly how skinny she is 
He took her to school this morning and so prepared her lunch, too. In her breakfast and lunch I'd say there was at least 35 spoons of sugar altogether. She already has two fillings and he has been asked to reduce sugar but still remains convinced that what he feeds her is fine. If I bring up her weight/diet with him, he says it must be my fault because she's here more but I have to restrict her a lot because of how much she's eating there. Aibu to feel utterly helpless here? She was absolutely down in the dumps after school and craving sugar to fix it.