Plot: Saskia Roberts, a 23-year-old Caribbean cuisine enthusiast, trades diets with 25-year-old food analyst Nick Harvey, who refuses to eat anything without identifying its contents first. Dr Christian Jessen also visits Evansville, Indiana, to tuck into a rack of baby back ribs containing 2,300 calories, and introduces 30st Lisa Bockus, who had to terminate a pregnancy because of her weight (Christian Jessen)