A sizzling steak with a pat of butter on top. Tuna, trout, or herring. A pile of crispy french fries. A flaky biscuit or delicate pie crust. Sure, all have some fat in them - but which fats are good, which are bad, and which are somewhere in between? Join Joe Palca and his guests in this hour of Science Friday as they try to sort out one fat from another and get the skinny on the latest nutrition research.

Plus, New York City is weighing a proposal to ban trans fats from the city's restaurants. Would such a ban save lives -- or is it, as some critics claim, just another case of the 'food police' getting unnecessarily involved in people's private lives?