Recent science has discovered that fats are not just good for us: Consuming healthy fats can lower our risk of disease and help us lose weight.
Fat is a macronutrient—emphasis on nutrient. All living things need fat. For optimal functioning, our brains must be more than half fat. We need fat to make and nourish cells; cushion and protect organs and nerves; store vitamins and absorb minerals; and transport hormones and other nutrients throughout our blood. We also need fat for energy.
For a list of good fats see our article 12 Healthy Fats List.
In his books, Good Calories, Bad Calories and Why We Get Fat, investigative science journalist Gary Taubes outlines the trajectory that led us to believe fats are bad for us, and saturated fats, even worse. For detailed analysis of the theories that proposed fat to be bad and the research that has thoroughly debunked those theories, you can’t go wrong with Taubes’ books. Here’s the gist:
In the 1950s, a small but influential group of health professionals linked dietary fat to heart disease. Eventually the American Heart Association, Congress, the USDA and the National Institutes of Health followed suit. By the 1980s, an entire industry had grown up around nonfat and low-fat foods. The low-fat diets of the next two decades were supposed to help people lose weight and reduce their risk of heart disease.
Now consider this: In the 1960s, the calories in the average American diet were nearly half from fat. Today, that number has decreased to about one-third of our calories. Back in the 60s, only 13 percent of Americans were obese. Today, more than a full third of American adults are obese. If looking to the past isn’t enough validation that lowering fat intake isn’t the answer, recent research shows that a diet in which half the calories are fat-derived is not linked to weight gain and disease.
Assessing a mountain of science on diet for more than a decade led Taubes to form this conclusion:
“Much of what we’ve been taught since the 1970s is simply wrong. This might explain why those same years have seen unprecedented increases in obesity and diabetes. When I started my research, I had no idea that I would come to such contrarian views. But now I think certain conclusions are virtually inescapable:
• Obesity and being overweight are not caused by eating too much fat.
• Easily digestible (refined) carbohydrates and sugar are the primary cause of excess weight.
• Dietary fat, saturated or not, does not cause heart disease.
• The foods that make us fat—easily digestible carbohydrates and sugars—eventually cause the diseases most likely to kill us: heart disease, diabetes and most cancers.”
Taubes is not alone in his viewpoint. Numerous scientists, physicians and investigative journalists are changing their tune about fat. Last fall, the British Medical Journal printed an article by cardiologist Aseem Malhotra showing a mound of research to indicate that reducing natural fat (and in its stead increasing sugar, empty carbs and trans fats) has led to huge spikes in obesity. Mark Bittman, the acclaimed New York Times food writer, dedicates a chapter in his new diet book Eat Vegan Before 6:00 to helping dieters understand the importance of consuming healthy macronutrients, fat among them. “Fortunately current research has forced a dramatic change to how scientists view the role fats play in health and weight loss,” he writes. Instead of avoiding dietary fats, he wants his readers to understand better which fats to eat—and then to eat them.
Fats are classified according to how saturated with hydrogen atoms their carbon chains are. In The Deluxe Food Lover’s Companion, Sharon Tyler Herbst and Ron Herbst describe the three classifications of saturation. “Picture a fat molecule as a train of passenger cars (carbon atoms). If every seat on the train is filled by a ‘passenger’ (hydrogen atom), then this is a saturated fat molecule. If there’s one seat open in each car where a hydrogen-atom ‘passenger’ can sit, the molecule is monounsaturated; if there are several seats available, it’s polyunsaturated.”
These distinctions are important because these fats behave differently in the body and in the kitchen. Most fats are composed of both saturated and unsaturated fatty acids, but are grouped according to the predominant one. Animal fats, about half saturated and half unsaturated, are usually solid at room temperature and referred to as saturated fats. Fats from vegetables, nuts and seeds are predominantly unsaturated, and are liquid at room temperature.
Monounsaturated fats figure largely in the famously healthy Mediterranean diet. They are associated with healthy insulin sensitivity, lower both bad cholesterol (LDL) and triglycerides, and reduce inflammation—which leads to a host of diseases. The very best source of monounsaturated fat is macadamia nuts, making macadamia nut oil supremely healthy. Olive oil, avocado oil, fish oil and many other kinds of nut and seed oils are also high in monounsaturated fats.
Polyunsaturated fats improve cholesterol and blood pressure, control inflammation, stabilize heart rhythms, and protect against all kinds of disease, including heart disease and cancer. The famous omega-3 and omega-6 fatty acids (more on these later) are polyunsaturated fats. Polyunsaturated fats are found in sunflower seeds, corn, soybeans, some fish, flax seeds, walnuts and animal fats (if the animals are grass-fed).
Typically solid at room temperature, saturated fats occur naturally in animal products such as meat, cream, butter, lard and cheese. Compared with unsaturated fats, saturated fats are likely less healthy—they may have adverse metabolic effects. Yet, despite a long-held belief that saturated fats harm heart health, researchers today are beginning to believe that saturated fats aren’t so bad for us. “When saturated fat got mixed up with the high sugar added to processed food in the second half of the 20th century, it got a bad name,” says pediatric endocrinologist Robert Lustig in an article in the Los Angeles Times. But is saturated fat or added sugar worse? “The American Heart Association has weighed in,” Lustig says. “The sugar, many times over.”
Some fats are decidedly not good for us, namely man-made trans fats. These include margarine, vegetable shortening, and the fats and oils in many processed foods. These fats are created when food manufacturers hydrogenate liquid fats, making them solid rather than liquid at room temperature, done to extend shelf life and create appealing textures. We now know that this is a terrible idea, and can lead directly to heart disease by spiking bad cholesterol (LDL) while reducing good cholesterol (HDL). Check ingredients lists for the words “partially hydrogenated.” Any partially hydrogenated oil is a trans fat. Avoid these like the plague.
In our bodies, fats of all types are broken down into fatty acids. Polyunsaturated fats include omega-3 and omega-6 fatty acids, which are essential—our bodies require them to function but can’t manufacture them. Both of these fatty acids are valuable, but the ratio we consume is important.
High ratios of omega-6s to omega-3s are associated with inflammation, cancer and a number of diseases. Early hunter-gatherers are estimated to have consumed a ratio of omega-6s to omega-3s between 1:1 and 4:1—two to four times as many omega-6s as omega-3s. The average American today consumes an omega-6 to omega-3 ratio at 20:1 or higher, because omega-6s are now easy to come by in highly refined vegetable oils, which are abundant in processed and fried foods.
Omega-3 fatty acids are rarer. The best sources are oily fish, shellfish, walnuts, flax seeds, chlorella (a type of microalgae) and fats from healthy animals that are grass-fed, including the fats in dairy, eggs and meat. According to the Harvard School of Public Health, omega-3s from fish and shellfish have more powerful benefits than those from plant sources. Omega-3s promote immune function; heart and brain health; good circulation; healthy blood pressure and glucose metabolism; and may even alleviate some mood disorders and behavioral problems. Andrew Stoll, a physician at Harvard Medical School and author of The Omega-3 Connection, estimates that improved omega-3 intake could save 70,000 lives a year in the U.S. For the average person, the easiest way to consume omega-3s is to eat fish twice a week. If you aren’t doing that, supplements may be the way to go. Omega-3 supplements are recommended for those with coronary heart disease; discuss it with your health-care practitioner.
Culinarily, fats are essential, too. They add moisture and richness to foods. They tenderize baked goods by lubricating starches and proteins. They also make everything taste better. A 2010 study published in the British Journal of Nutrition found that in addition to sweet, sour, salty, bitter and savory, the human tongue can also detect the taste of fat.
The choice of solid and liquid fats is important to the cook. The high boiling point of many liquid fats (oils) means they can be used to create the intense flavors that come from browning reactions. Solid fats are more stable at room temperature. You can create soft pastries with solid fats because butter traps lots of air when creamed with sugar. You can build the coveted flaky pie crust with butter or lard because they remain solid until heated, at which point they melt and leave pockets of air between layers of flavorful dough.
Besides being useful to create textures and browning reactions, all fats add their own flavor. For example, almond, hazelnut and walnut oil are prized for their fine flavors—try them on salads. If you look beyond the big-box grocery store, olive oils come in a wide range of bold flavors, from fruity and grassy to peppery. Sesame seed oil lends an unmistakable savory flavor to Asian food. Dark green pumpkin seed oil makes a memorable salad dressing.
If you love flavor, you might want to stock your pantry with a wide variety of fats and oils—you will be outfitting your diet with a wide variety of nutrients.
Beware that what is labeled “extra-virgin olive oil” may not be. A 2010 study from the University of California, Davis, tested extra-virgin olive oils and found that 70 percent of imported samples and 10 percent of California samples labeled “extra-virgin” failed to meet standards for extra-virginity, either because they were adulterated with refined oils or because they were oxidized from heat or improper handling.
Tom Mueller, author of Extra Virginity: The Sublime and Scandalous World of Olive Oil, offers a checklist for finding the real stuff at truthinoliveoil.com. Because olive oil begins to degrade when exposed to heat, light and oxygen, Mueller’s tips include choosing olive oil from the nearest possible milling source, opting for oils in dark bottles with a harvest date printed on them, and storing those bottles in a cool, dark spot. Most important, don’t forget to use your best oils while they’re still in top form!