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The Skinny on Fat: Good Fats vs. Bad Fats

How fats fit into your healthy diet.

Good Fats vs. Bad Fats

Basically, there are two groups of fats: saturated and unsaturated. Within each group are several more types of fats.

Let's start with the good guys -- the unsaturated fats. Unsaturated fats include polyunsaturated fatty acids and monounsaturated fats. Both mono- and polyunsaturated fats, when eaten in moderation and used to replace saturated or trans fats, can help lower cholesterol levels and reduce your risk of heart disease.

Polyunsaturated fats, found mostly in vegetable oils, help lower both blood cholesterol levels and triglyceride levels -- especially when you substitute them for saturated fats. One type of polyunsaturated fat is omega-3 fatty acids, whose potential heart-health benefits have gotten a lot of attention.

Omega-3s are found in fatty fish (salmon, trout, catfish, mackerel), as well as flaxseed and walnuts. And it's fish that contains the most effective, "long-chain" type of omega-3s. The American Heart Association recommends eating 2 servings of fatty fish each week.

"Plant sources are a good substitute for saturated or trans fats, but they are not as effective as fatty fish in decreasing cardiovascular disease," notes Lichtenstein. Do keep in mind that your twice-weekly fish should not be deep-fat fried!

It is best to get your omega-3s from food, not supplements, Lichtenstein says: "Except for people with established heart disease, there is no data to suggest omega-3 supplements will decrease heart disease risk."

The other "good guy" unsaturated fats are monounsaturated fats, thought to reduce the risk of heart disease. Mediterranean countries consume lots of these -- primarily in the form of olive oil -- and this dietary component is credited with the low levels of heart disease in those countries.

Monounsaturated fats are typically liquid at room temperature but solidify if refrigerated. These heart-healthy fats are typically a good source of the antioxidant vitamin E, a nutrient often lacking in American diets. They can be found in olives; avocados; hazelnuts; almonds; Brazil nuts; cashews; sesame seeds; pumpkin seeds; and olive, canola, and peanut oils.

The 'Bad' Fats in Your Diet

Now on to the bad guys. There are two types of fat that should be eaten sparingly: saturated and trans fatty acids. Both can raise cholesterol levels, clog arteries, and increase the risk for heart disease.

Saturated fats are found in animal products (meat, poultry skin, high-fat dairy, and eggs) and in vegetable fats that are liquid at room temperature, such as coconut and palm oils. The 2005 Dietary Guidelines recommend limiting saturated fats to 10% or less of your total calories, while the American Heart Association recommends keeping them to just 7% of total calories.

Lichtenstein recommends using liquid vegetable oils in place of animal or partially hydrogenated fats.

"There is evidence that saturated fats have an effect on increasing colon and prostate cancer risk, so we recommend whenever possible to choose healthy unsaturated fats -- and always strive to be at a healthy weight," Doyle explains.

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