Fats eaten in moderation keeps those extra pounds away. No, we're not kidding: Harvard researchers found that moderate-fat diets actually produced better long-term weight loss results than low-fat diets. The key is knowing which fats are figure-friendly, and which hurt your waistline, say experts.

The truth about fat

Fat -- in the right amount -- is an essential part of a healthy diet and one of its main purposes is to store energy for your body's vital functions. But because of the readily available high-fat junk food and fast food nowadays, we're living in a generation of excess, so to speak. As a rule of thumb, because all fats are high in calories, dieticians advise limiting all fat intake to less than 25 to 30 percent of your total daily calories. Especially steering clear of the 'bad' fats.

But what makes a fat 'good' or 'bad'? The simple answer: Its effect on our cholesterol. You see, our body has 'good' HDL cholesterol (that lowers risk of heart diease) and 'bad' LDL cholesterol (which increases your risk). "Eating the right kind of fat, the good fat, actually improves your heart health," explains Dr. Matthew S. DeVane, cardiologist and author of Heart Smart. "Eating bad fats, on the other hand, is basically like spoon-feeding LDL cholesterol right into your heart arteries."

Avoid the 'bad' fats

"Saturated and trans fats raise LDL cholesterol and increase your risk for coronary heart disease -- they're the bad fats," adds DeVane.

Saturated fat

Saturated fats occur naturally in animal products, including fatty meats, whole milk, ice cream, cheese and butter as well as some vegetable oils such as coconut and palm. Limit these to less than 7 percent of your total daily calories.

Trans fat

Trans fat is added to many convenient foods to extend their shelf life and lurks in French fries, margarine as well as commercially baked foods -- think doughnuts, crackers, cookies and muffins. Trans fat is considered especially bad, because it not only increases the bad cholesterol but also lowers the good cholesterol in your body -- a double whammy. "They are largely accountable for the current epidemic of obesity and elevated cholesterol in children, adolescents, and adults," says DeVane.

You should eat as little of trans fat as possible. When shopping for groceries, look at the food labels and avoid those that contain "hydrogenated", "partially hydrogenated", "trans fatty acids", or "trans fat" -- these are essentially codewords that trans fat is present.