New research shows people who cut back on carbohydrates will burn more calories than those who cut back on fat.
The idea behind the National Institutes of Health and the New Balance Obesity Prevention Center study was to see what kind of diet would help people keep weight off once they had lost it.
Researchers found people burned the most calories a day on the low-carb diet.
But experts warn that a diet too low in carbs and too high in fat can lead to heart problems.
Consequently, some recommend a low glycemic diet that includes eating carbs based on whole grains.
"If you eat healthier, more clean carbohydrates, complex carbohydrates low on the glycemic index like brown rice, bran, whole grains and high fiber beans, those things that really help stabilize your blood sugar and take a little bit more go burn and that's more calories that you're burning," dietitian Karin Hosenfeld said.
"The low-glycemic diet reminded me of the way my mom and grandmom cooked while I was growing up," study participant Mike Roger said. "I felt far better on the low-glycemic diet than on either of the other two."
The study was published in the Journal of the American Medical Association.