Since the last year or so, my daughter has gained an unhealthy amount of weight. As parents, my wife and I know that weight is a sensitive issue for pubescent girls, so we haven't openly discussed it with her yet. We do however (and always did) try to lead by example. My wife and I are both active rockclimbers and try to eat as healthy as we can. We count the calories of our and our daughters meals, and this is why we're surprised about her massive weight gain.
How could we as parents approach this problem in a sensible manner?