Too many people believe that “a calorie is a calorie is a calorie.” They think that a diet will be successful as long as they achieve the perfect calorie count — and that it doesn’t matter whether that number comes from potato chips or carrot strips.

Not so, it turns out. After 12 years of following the food choices of 120,877 American men and women, Harvard University researchers learned that people who consumed the same number of calories in products such as potato chips and sugary soft drinks gained weight, while those who ate yogurt, fruits, and berries got slimmer.

Overall, the participants who ate junk food gained an average of about 13 pounds over the 12 years. Not surprisingly, the people who exercised more gained less weight, and the most fattening habit identified was TV watching — because people tend to snack while they watch.

So get up off the couch and grab a cup of yogurt instead of the chips. You’ll feel healthier today, and you’ll be slimmer in the long run.