Fat is a dietary evil - or so you may have heard. Not only are fats a more concentrated source of calories than carbs or proteins, but studies indicate that the body more readily stores fats. So a diet rich in high-fat foods make you gain more weight. Plus, some types of fats have been implicated in a higher risk of heart attack, diabetes, and other diseases.

But the truth is that fat, in small amounts, is essential to health. Some fats, like those found in fish and olive oil, actually lower your risk of heart disease and can even help you stick to a weight loss plan.

Fats add flavor and a smooth, pleasing texture to foods. Because they take longer to digest, fats let us feel full even after the proteins and carbohydrates have left our stomach. Fats also stimulate the intestine to release cholecystokinin, a hormone that suppresses the appetite and signals us to stop eating.

Fats supply the fatty acids that are essential for numerous chemical processes, including growth and development in children, the production of sex hormones, and prostaglandins, the formation, and function of the cell membranes, and the transport of other molecules into and out of cells.

Finally, fats are needed for the transport and absorption of the fat-soluble vitamins A, D, E, and K. A tablespoon of vegetable oil is sufficient to transport all the fat-soluble vitamins we need in a day.

American and Canadian nutritional authorities recommend that adults restrict their total fat intake to 20 to 35% of each day’s calories. If you’re getting 2,000 calories per day, that works out to 44 to 78g of fat daily, most of it ideally the unsaturated kind.

As with carbohydrates, the type of fats we eat is more important than the total amount. Fats fall into two main categories: saturated and unsaturated. Most foods naturally contain both types but are higher in one. In addition, many commercially produced foods are made with trans fats, which are rarely found in nature.

Fat Facts

1. All fats contain the same number of calories by weight; that is, about 250 calories per ounce, or 9 calories per gram. Volume for volume, however, the calorie count can differ substantially. For example, a cup of oil weighs more — and therefore has more calories—than a cup of whipped margarine.
2. In North America, daily fat intake has increased over the years to 35 to 40% of our daily calories. This is the equivalent of approximately 90 g of pure fat a day—almost exactly the amount in a stick of butter — and it’s much more than we need.

Saturated Fats

Saturated fats generally come from animal sources, but there are some plant sources as well. Common sources of saturated fat include meat, poultry, butter, cheese, and coconut and palm oils. Most saturated fats are solid at room temperature. A diet high in saturated fats can raise blood cholesterol levels, one of the leading risk factors for heart disease. Saturated fat has also been linked to other health problems, such as colorectal, prostate, and ovarian cancer. Experts recommend that no more than 10% of your daily calories come from saturated fat, especially animal fats. (Some researchers believe that the type of saturated fat in coconut oil increases good HDL cholesterol as well as bad LDL cholesterol, so it’s been touted as more of good fat in recent years.)

Unsaturated Fats

In general, unsaturated fats are healthier than saturated fats; they either lower blood cholesterol or have no effect on it, and may also help lower blood sugar and blood pressure. Most unsaturated fats are liquid at room temperature and solid or semisolid under refrigeration. Unsaturated fats fall into two main categories: monounsaturated and polyunsaturated. Polyunsaturated fats, in turn, are divided into omega-3 and omega-6 fats. Each type affects your health in different ways.

• Monounsaturated Fats (sometimes called MUFAs) improve blood cholesterol levels and may benefit insulin levels, thus lowering your risk of heart disease and type 2 diabetes. Major food sources include olives, nuts, avocados, and olive, canola, and peanut oil.

• Omega 3 Fats help steady heart rhythm, lower artery-clogging triglycerides, cool chronic inflammation in the arteries, prevent blood clotting and produce a modest drop in blood pressure, all of which cut your risk of a heart attack or stroke. Findings from 30 large studies conducted around the world show that people who consume just 1 or 2 servings of omega-3-rich fish per week lower their risk of a fatal heart attack by an average of 36%. And mounting evidence suggests that omega-3 fatty acids help the brain with its normal day-to-day function. Omega-3 fats are found in fatty fish such as salmon, mackerel, herring, and sardines, as well as flaxseed, walnut, and canola oils and some newer products such as omega-3-rich eggs.

• Omega 6 Fats, on the other hand, increase inflammation if you consume too much. Omega-6 food sources include safflower, sunflower, and corn oil, and some nuts and seeds. While there are a variety of opinions on the optimal ratio of omega-3 to omega-6, experts agree that we tend to eat far more omega-6 fats than we need and too few omega-3s.

Trans Fats Trans fats are created when a vegetable oil undergoes hydrogenation, a process that lengthens foods’ shelf life. Trans fats are found in:

1. Partially hydrogenated vegetable oils
2. Some margarine
3. Crackers
4. Cookies
5. Commercially fried foods

Hydrogenation makes polyunsaturated vegetable oils act like saturated fats: They raise LDL cholesterol levels. Thus, nutritionists recommend that you consume as few trans fats as possible.

Fortunately, many people seem to have gotten this message in recent years. In the past few years, the trend has been for manufacturers and restaurants to cut back on trans fat in their foods. In a study from 2012, researchers compared blood samples from white adults taken in 2000 and 2009. Levels of trans fat in the samples fell by 58% during this time. Along with this change came a drop in LDL (“bad”) cholesterol.