Fat has quite the reputation as a dietary supervillain, but there's more to fat than that.

A little dietary fat is essential for good health. In addition, some types of fat (in modest amounts) may even help protect your health. Other fats, however, may harm your health if you eat them too much.

Here's a closer look at these bad and good fats.

The bad guys: Saturated and trans fats

These two fats raise LDL blood cholesterol—and with it your risk of heart disease and stroke:

Saturated fat. This is found mostly in animal products including red meat, lamb, chicken with the skin left on, butter, cheese, and full-fat or 2 percent milk. It's also in some plant foods, such as coconut oil, palm oil and cocoa butter.

Trans fat. This is found in foods with hydrogenated or partially hydrogenated vegetable oil, including baked goods such as cookies, pies, doughnuts and snacks. It helps them have a long shelf life. Trans fat is also in some fried restaurant foods.

The good guys: Unsaturated fats

Eating healthy, unsaturated fat instead of saturated fat may help improve cholesterol levels. The two main unsaturated fats are:

Monounsaturated. Examples of foods that contain monounsaturated fats include olive and canola oil, nuts, peanut butter and avocados.

Polyunsaturated. Examples of foods that contain polyunsaturated fats include salmon; tofu; and safflower, sunflower and corn oils.

To help keep your diet focused on the good fats:

• Plate up more fruits, veggies and whole grains, and less red meat.

• Switch to low-fat or non-fat milk.

• When sautéing or stir-frying, use olive, canola or other oils.

• Eat fish at least twice a week.

• Choose soft margarine instead of butter. Look for "0 grams trans fat" listed on the label.

• Save sweets like doughnuts, cookies, pies and cakes for the occasional treat.

Sources: American Heart Association; American Academy of Nutrition and Dietetics