Is it such a bad thing that they compare themselves to their peers?
In 2018 "obesity prevalence was [...] 21.2% among 12- to 19-year-olds." [1] according to the CDC. That's one out of 5 being obese, not just overweight. And it has more than tripled since the 70's [2]. I have to wonder if it's related. A lot of teenagers are bombarded with images of their peers' perfectly healthy bodies that, quite simply, won't match what they see in the mirror. The solution? Ban mirrors.
[0] https://www.cdc.gov/obesity/data/childhood.html
[1] https://www.cdc.gov/nchs/data/hestat/obesity_child_15_16/obe...