A new study looks at whether adhering to a low-carb diet or a low-fat diet has a better chance of extending your lifespan. The study, published in the Journal of Internal Medicine, analyzed dietary data from more than 370,000 middle-aged and older adults. It concluded that consuming a low-fat diet full of healthy foods during middle age may lengthen your life. In contrast, a healthy low-carbohydrate eating pattern did not lead to much of an improvement in longevity. The new study comes on the heels of a new evaluation of popular diets by the American Heart Association, which rated DASH, Mediterranean, vegetarian and pescatarian diets as the most heart healthy, while giving mid-range scores to low-fat and low-carb diets.