Here is my situation.
Dd was always a healthy weight. She started secondary this year and between September and Christmas noticeably put on weight. We noticed. She wasn't happy either, we could see it. She hated going out.
I spoke to her about talking about health and the impact, her weight had on the sport she does.
I took her off the canteen food and put her on sandwiches and it fell off. They sell so much unhealthy food she wasn't able to resist the pancakes and have toast (she had breakfast at school as she could face breakfast to early). Or resist the sandwiches covered in mayo and a cookie.
So she went on sandwiches and the weight came off. I have spoken to several parents of kids in her year and all said their kids have put on a lot of weight since starting.
Some have done something, some have ignored it through fear of upsetting their kids. Some have ignored it and said 'well it's their choice and their problem.
One parent, whose son has stacked on a lot of weight (he now looks severely obese) insists its his natural build and he doesn't eat much. Which isn't true, he has lunch with dd and eats loads. She must know he eats a lot as she give him the money.
I think someone needs to step in and wake her up.
Personally I think they 'it's their choice and their problem' are being neglectful. They aren't trying to educate their kids or help them.
If your kids were doing something else that was so dangerous to their future health you would step in.