10 Causes of Weight Gain That Doctors Have Changed Their Minds About

Eating Full-fat Makes You Fat
For years, people were told to cut back on fat -- and we did but we got fatter anyway. Doctors now believe that fat was not cause of our obesity epidemic. Dave and Les Jacobs/Lloyd Dobbie/Blend Images/Getty Images

If you're a fan of indie cinema, you probably remember that scene from the 2004 coming-of-age hit "Napoleon Dynamite," in which the awkward protagonist tries to make conversation with a girl he likes: "I see you're drinking 1 percent. Is that 'cause you think you're fat? 'Cause you're not. You could be drinking whole if you wanted to" [source: IMDB].

That movie scene is funny, in part, because it reminds us of the popular belief that when you eat or drink foods rich in fats, your waistline and butt will expand as a consequence. But as an article on the Harvard School of Public Health's website explains, studies show that the proportion of fat in a person's diet doesn't really have much effect upon weight. In fact, over the past 30 years, while the percentage of calories from fat in the typical American diet has gone down, obesity rates have skyrocketed.

Again, it mostly comes down to calories. Many low-fat diets are full of carbohydrates (like white rice and bread) which can cause weight gain. That said, the type of fat does matter − try to consume more monounsaturated and polyunsaturated fats and less saturated fats. Saturated fats are found in products like butter, cheese and red meat [source: Harvard School of Public Health].