There's more to dieting than losing weight, because how you eat can affect your cholesterol levels. Researcher Gary Foster, director of Temple's Center for Obesity Research and Education, looked at two years of data that compared low carb and low fat diets. Foster says people lost about as much weight on either. But he found a difference in HDL cholesterol — what's called "good" cholesterol, because it seems to protect against heart attack: "Patients on the low-carbohydrate diet experienced a 23 percent increase in their HDL cholesterol, compared to about a 10 to 12 percent increase for those on the low-fat diet." Foster says it's something for people who need to raise their HDL to keep in mind.