Several web sites have sound samples of Edmundo Ros performing IT'S ILLEGAL, IT'S IMMORAL, OR IT MAKES YOU FAT on the album of the same name. I was able to transcribe this much:

...who first said
That it's illegal, it's immoral, or it makes you fat.
It really doesn't matter what you're aiming at.
If there's something you enjoy, you can be certain that
It's illegal, it's immoral, or it makes you fat.

When you go on a diet, though you cut out all your beef,
Eat lots of spinach or a lettuce leaf,
You'll notice that all your favorite recipes
Are the ones that have too many calories.
It's illegal, and it's immoral.
It's illegal, it's immoral, or it makes you fat.

There are plenty of things that you are free to do
Without anyone trying to...