3. False. For a diet to be low in fat, no more than one-third of the calories should come from fat, but one recent study showed that people who ate slightly more than that—33 percent of their calories came from fat—lowered heart disease risk by 14 percent. Those who ate an extremely low-fat diet, with less than 25 percent of the calories from fat, only lowered their heart disease risk by 9 percent. It turns out it’s not the total fat that matters the most, but what kind of fat—which means it’s better to consume more oil than butter.