Today, after a lot more scientific research, we know that not all fat is bad and, in fact, some fats are crucial to a healthy body.

Now we need to pay more attention to the quality of fats in our daily diets and not just the quantity.

There are four basic types of dietary fat: saturated fat, trans fat, monounsaturated fat and polyunsaturated fat.

Saturated fat comes from red meat, full-fat dairy products and some tropical oils. This fat has documented negative health impacts. It can increase a person's risk of heart disease, stroke, and some cancers, as well as increasing the danger of becoming obese and diabetic.

Trans fats are probably worse than saturated fat and we do not need to eat any of these. Among other problems, trans fats are associated with a decrease in the ability of insulin to do its job. Trans fats come from partially hydrogenated vegetable oil and were originally developed to help give packaged processed food products a longer shelf life.

Monounsaturated fats are good fats. These are the fats in olive oil and canola oil, as well as avocados. Monounsaturated fats can protect your cardiovascular system and lower your risk of insulin resistance, which can lead to diabetes.

Polyunsaturated fats include omega-6 and omega-3 fatty acids. Our diet must include these fatty acids because our bodies can't manufacture them. Most people do not need to worry about getting enough omega-6 because our Western diet is overloaded with them. We get omega-6 from corn oil, safflower oil, cottonseed oil and sunflower oil. These fats are in most packaged foods.

Omega-3 fats come from two sources: plant sources like walnuts, flaxseeds and dark leafy greens, and marine sources, such as wild salmon, Alaskan halibut, tuna and sardines.

Omega-3 fatty acids help build ideal cell membranes and promote the production of prostaglandins. Without these, we increase our risk for many health problems, including stroke, heart attack, cardiac arrhythmias, some cancers, insulin resistance, asthma, hypertension, age-related macular degeneration, autoimmune disorders, and ADHD. Other problems include dry skin, brittle nails and hair, constipation, frequent colds, inability to concentrate, depression and joint pain. One report found that almost 99 percent of Americans do not consume enough omega-3 fatty acids.

Today, we no longer need to look for 'fat free' food. Instead we need to pay attention to the type of fats in our diet. We should be increasing amounts of omega-3 fatty acids and monounsaturated fats in our diet and decreasing our intake of omega-6s. Saturated fats should be a very minor part of our daily diet and we should avoid all trans fats. For recipes that incorporate omega-3s and monounsaturated fats see pages 122, 217, 219, 222 and 252 of our bestselling book, SuperFoodsRx, Fourteen Foods That Will Change Your Life.