"My daughter denied knowing me to friends at school because I'm overweight"

I have a daughter in 8th grade, her school had an event on Friday that I picked her up from. The event was in the gym and there were a mixture of parents who were just waiting in the parking lot outside but also a lot were going inside so I decided to as well, it was some big start to the holiday season/winter event so I wanted to see how they gym was decorated.

Anyway, me going inside was kind of an impromptu thing. I went into the gym and after a minute or so spotted my daughter who was standing around with a few other girls. They started walking in my direction and I waved to flag her down, she looked at me quickly but walked right passed me even when I tried to talk to her. I just kind of stood there confused and watched her say bye to these girls and then went directly into the locker room without coming over or acknowledging me. I didn't feel comfortable going into the kids' locker room so I just stood and waited for a few minutes and then got a text from her saying she'd meet me in the car. I didn't think much of it, I thought maybe she was busy talking and didn't want me to stand around and wait longer.

I went back to the car and she came out just a few minutes later. This is when I realized something was off. Those same girls she was talking to before in the gym started to walk by my car and my daughter actually ducked/tried to cover her face from them seeing her. I said what are you doing??? She told me to just drive and leave already. Her and I are close and she doesn't normally snap at me so I didn't know how to respond. I started driving and we just sat there in silence for a minute and then I asked her if she wants to tell me what's going on.

She told me she was sorry but she didn't want anyone to see her with me. I asked why and my jaw nearly hit the floor when she said it's because of how I look (there's literally nothing she could be referring to here other than my weight) and she didn't want to get picked on over it. I could stand to lose about 40-50lbs but I'm not to the point of public spectacle so I was shocked and confused. I told her that really hurt my feelings and I didn't understand where it was coming from and then she started crying saying she's fat and she didn't want the kids to see me and think we're the “fat family”. My daughter is NOT fat, she has a naturally wider frame but does several sports and is very active and healthy.

I had no idea she felt this way about herself which broke my heart even more than her apparent embarrassment of me. I assured her she's not fat at all and those girls wouldn't ever have those thoughts if they're her real friends and I sympathized with how she felt but to ignore me in public the way she did wasn't okay. She apologized and it's over now but geez, I've never felt so bad about myself.

I guess I'm just trying to vent and also get some advice as a parent with a young teen who is clearly starting to have body image issues.