By Hadas Kuznits

PHILADELPHIA (CBS) – A new book on Junk Food examines why the bad stuff is so good.

Andy Smith, Food Department professor at New School University in New York was at the Restaurant School in Philadelphia talking about his new book, “Fast food and Junk Food an encyclopedia of the foods we love to eat”.

“I’ve worked on this for 50 years and I’ve been feeling obligated to make sure I sampled every single thing that I wrote in my two-volume encyclopedia,” said Smith.

So why is the bad stuff so good?

“We’re physiologically predisposed towards fat, salt and sugar so those are the things that make junk food, junk food and evolutionary, those are the things that we needed. Today we don’t need them as much as we did 10,000 years ago and so that’s the problem.”

Smith says another reason we’re so drawn to junk food is marketing.

“They’ve got a lot of money and they know exactly who their audience is, which usually is kids and families with children.”

And he says junk food tastes vary by region.

“Each culture has their own levels of salt and levels of sugar and levels of fat and it certainly varies from group to group.”

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