[Fathom Zero]

Dude, I ain't fat. I've got a high metabolism which keeps me fit.

It's kind of like that episode of X-Files where the genetically engineered tobacco plants have eggs on them and this dude is the beta test for it. The eggs are deposited in the guy's lungs, because the smoke carries them. Everyone around him dies while he doesn't.
Why? Because the addiction keeps them at bay. What's killing him is keeping him alive, long story short.

I give my metabolism a workout that keeps it fit.