Is it bad for a 12-year-old to lose weight?

Well, it really depends on your frame. I mean, I'm twelve and I weigh 8 stone and I keep on asking people, am i overweight? They all say no because your body is mostly muscle. So if you are 8 stone or under you are absolutely fine but if your over, maybe you could do some fat burning. Although, if you are concerned about your weight, ask your mum or dad if you are overweight. They will tell you the truth.