Fast Food Study Pays to Gain Weight

And you wonder why America is obese...

ABC News' Nightline delved into a big experiment where researchers at Washington University in St. Louis asked participants to go on an 18-week high-calorie diet followed by a workout program. Dave Giocolo, who considered the challenge a dream come true, became one of the subjects to consume 1,000 calories a day of greasy, fast food and get paid for it.

The goal of the doctors conducting the experiment was to figure out why some who gain weight also suffered from diabetes and hypertension while others did not, a study they could not conduct by feeding lab animals food pellets. The cash incentive was up to $3,500 depending on how much weight the participant could gain. Medical authorities then guided them to lose the pounds.

Can't believe it? Watch the full segment below.