You’d be surprised. A friend’s 11-year-old daughter who is athletic and slim just got diagnosed the other day, and she is getting a CPAP. Frankly, I think there’s a lot of confirmation bias because fat people who snore are much more likely to go in for a sleep study.
Yeah obesity is definitely associated with obstructive sleep apnea, no doubt. But what if they just have a thick neck and are otherwise healthy? I'm willing to give the benefit of the doubt