As an extremely overweight child, Nick Feltus was mercilessly harassed by the other kids. Now, Nick is the well-toned owner of the gym “Physique”, along with his buddy Denis. Surprisingly, Nick feels nothing but disdain for fat people – people like Eva. But fate is about to teach him a lesson.
The day after taking a terrible fall from a rooftop, Eva wakes up – suddenly slender – while Nick is now a blubbery 400 pounds! His new condition leaves him stuck in doorways, a destroyer of chairs and toilets, and once again a target of disgust.
When Nick runs into the thin Eva, realizing what must have happened, he grabs her and leaps from a window with the hope of reversing the effect – but to no avail.
Nick must prove to Denis he is in good enough shape to run a gym. He undertakes fitness training – with Eva as a partner. Eventually, Nick does pass his physical, but then Denis blackmails him with a secret agreement stating only slim people may become “Physique” members.
Nick and Eva organize a “Fat in” at the gym to draw attention to the plight of the obese, but when its members quit rather than having to train alongside fat people, Nick loses the gym…