daughter 15 heavy

I used to be that daughter who got too heavy. When my mom started bringing it up, I became really insecure and ended up eating a lot of sweets. It wasn’t until I hit 100 kilos as a teenager that I had enough of it myself and wanted to lose weight.

You could suggest going to the gym together? That way you can say you just really want to do something together.
Also, make sure there's lots of healthy food at home, and don't bring sweets and unhealthy stuff into the house. Or at least as little as possible.

Talk to your GP first. You can actually do a lot yourself by adjusting your home meals. By cooking differently and buying different products.

It's normal for teens to gain some weight and temporarily look a bit fuller. But it shouldn't spiral out of control.

Is she doing sports? Is she active enough? Do you know why she's gaining weight? What exactly is she eating too much of? Do you know if she's happy? This is such a vulnerable age. I'd really try to look at yourself and your family dynamics first, rather than putting the blame on your daughter. She probably started overeating for a reason.

It’s never okay to say this to your daughter.
Your daughter is still developing and is currently going through puberty. She’s searching for herself. If she hears that she’s not good enough as she is, it could cause serious emotional problems and even lead to eating disorders.
It’s important that your daughter feels good in her own skin.

Sandy has a point. It might sound harsh, but pushing often backfires. I remember how I looked and didn't want to hear it either. Focus more on having a healthy relationship with food, not on the number on the scale. A chat with the GP might bring some peace of mind, but try to support her for who she is.