Fat is a dietary evil—or so you may have heard. Not only are fats a more concentrated source of calories than carbs or protein, but studies indicate that the body more readily stores fats. So a diet rich in high-fat foods makes you gain more weight. Plus, some types of fat 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 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.
• 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.
• 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.