Diet to GAIN weight

Matt Chaffee has to watch his diet.
Not to loose weight, but to gain it. The 22-year-old man from eastern Idaho now tops 100 pounds for the first time in his life.

He's going to celebrate with a special dinner out with his mom.

Chaffee says he's a medical mystery and had digestive problems as a newborn. The five-foot-nine college student consumes 6500 calories a day, more than 2.5 times average.

He boosts his intake with protein shakes and must wear long underwear even in the summer to keep warm.

Chaffee says his next goal is to get up 120 pounds.