They take someone who is anorexic, or has a hate relationship with food, etc...and only eats 1000 calories a day, and then they take someone who is morbidly obese, and eat's roughly 9000 calories a day, and they make them switch diets for one week, HA! It's brilliant...
Obviously that is just for dramatic effect, so they have a nutritionist/phsyc working with them beyond that to help them get back to normal...really great show













