Sherman Klump is an incredibly fat and good-hearted man. He is a college professor on the verge of a breakthrough in DNA restructuring when he meets an admirer of his, named Carla, who is a teacher new to Klump's college. He is enamored of her, but is frustrated by his tremendous bulk. He then decides to test a formula on which he's been working on himself. He is then transformed into the lecherous swinger, Buddy Love, and romantic complications ensue.