Health psychologist and eating behavior expert Charlotte Markey is kind and mild-mannered in person, or at least that's how she came across when she visited us in studio for a conversation about dieting. But her opinion of fad diets and get-slim-quick schemes is far less congenial than her personality.

The title of her new book says it all...Smart People Don't Diet: How the latest science can help you lose weight permanently.

In the era of no-carb, high-protein, gluten-free theories on dropping 20 pounds quickly, Markey advocates for foods and diets that take a long-term approach to weight loss.

"Most diet fads...are intended to be painless," she explained in our interview, "but usually they don't workout that way, and people may lose weight, but they usually just gain it back."

We talked to her about strategies for losing weight for good and the role our partners play in how much we weigh.