Well, if you eat too much, you’ll get fat. But it turns out that it does matter what you eat, as well:

Despite conventional advice to eat less fat, weight loss was greatest among people who ate more yogurt and nuts, including peanut butter, over each four-year period. . . . But, consistent with the new study’s findings, metabolism takes a hit from refined carbohydrates — sugars and starches stripped of their fiber, like white flour. When Dr. David Ludwig of Children’s Hospital Boston compared the effects of refined carbohydrates with the effects of whole grains in both animals and people, he found that metabolism, which determines how many calories are used at rest, slowed with the consumption of refined grains but stayed the same after consumption of whole grains.

Overall, this sounds pretty consistent with Gary Taubes’ thesis, which has become pretty popular in the blogosphere. Personally, I lost about 10 pounds last semester through a combination of the Livestrong app for my iPhone — which does count calories — and an increased avoidance of refined carbs, per Taubes advice. It was pretty painless.