How do you promote fitness in younger people?

You show teenagers PowerPoint presentations consisting of pictures of morbidly obese people. Whilst your slideshow's running , don't hesitate to supplement each picture with your very own preachy and anger driven comment about it " Look at this fat f*ck , over here. Is that how you want to end up ? Well ? Is it ? When's the last time do you think he's seen his penis ? "

Be consistent. Each comment must have the same level of cruelty as the previous one. It would be desirable if you can find a way to spew even more ferocious thoughts , but if you can't.. at least be consistent and have a very firm voice - with terrifying pictures and a proper speech , no one will dare to contest anything you say.