here's abc's juju >> reporter: katherine schreiber says she's addicted to something post people would praise her for. she's been known to hit the gym obsessi obsessively. >> this is my first love. >> two hours before work, an hour at lunch, another session after work. >> i don't stop because you're not worth [ bleep ] if you stop. you're worthless. >> katherine is a self-proclaimed exercise addict, but rather than make her happy, she thinks it's a curse. you know, when people don't know your back story, they look at your physique and say oh, i'm so jealous of her physique? >> absolutely. >> reporter: what would you say? >> it looks better than it feels. i'm so envious. it's not something to be envied. the psychological turmoil that drives me to do this, it's not fun and i don't wish it upon anybody. >> reporter: our country is in the grips of an obesity epidemic, which may explain the exponential growth of hyper intensive workouts that promise to help you slim down and bulk up quickly. p90x, selling more than 4 million dvds. insanity? more than 2 million. crossfit, signing up 10 milli