This is how to do a childhood obesity campaign.
Almost always, when health agencies execute these campaigns, they show — big surprise — obese kids, like a 2012 campaign via Children's Healthcare of Atlanta (one ad from the effort, below).
The only thing those type of ads accomplish is they make both children and parents feel worse. Everybody already knows what an obese kid looks like.
This Welsh (update: UK) campaign may very well not work, either. But that's a bigger problem: whether social PSAs ever work. "Just Say No" was a multi-billion dollar bust of an anti-drug effort.
On the opposite end of the mood spectrum, there was the below (bottom ad) obesity advert via Belgium. While it is a hilarious visual, I'm not convinced humor is the way to go, but it's definitely better than just showing overweight kids again and again.