The word fat has such negative connotations in our culture that many of us shy away from foods that contain it. But dietary fat is a very different thing than the fat cells we carry in our bodies—and we need to eat it for good health. Here are some of the most common misconceptions about the macronutrient called fat, and the truth that can really ease your mind (and improve your meals!).
Myth #1: Fat is terrible for your heart.
The truth: Many fats (such as omega-3 fats, some polyunsaturated fats, and virtually all monounsaturated fats) are very useful in preventing heart disease and improving memory, says Karol Watson, M.D., Ph.D., a professor of cardiology at the David Geffen School of Medicine at UCLA. These healthy fats—found in foods such as avocados, seeds, nuts, and fatty fish like salmon and tuna—may help lower total cholesterol and reduce inflammation, both risk factors for heart disease. The low-fat-everything diet craze of the ’80s was fueled by the wrongheaded belief that because some fats are bad for you, all fat must be bad. The ones to watch out for are trans fats (typically labeled as hydrogenated or partially hydrogenated oils) as well as most seed oils like corn, soybean, cottonseed, and grape-seed oils, which have high levels of the omega-6 linoleic acid. These raise bad cholesterol, which causes plaque to form in the arteries, and lower the potentially good kind. As for saturated fats—found in meat, butter, milk, cheese, and baked goods—the verdict is more complicated. Saturated fats raise levels of both good and bad cholesterol, so their impact on health is less clear. While the thinking about saturated fats is changing, current guidelines recommend keeping these to 10% or less of your daily calories.
Myth #2: High-fat foods are bad for your cholesterol.
The truth: It depends on the type of fat. Eating unsaturated fats, especially if they replace saturated and trans fats in your diet, can improve your cholesterol and protect against heart disease, according to the American Heart Association. These fats, usually found in plant-based foods and fatty fish, lower potentially artery-clogging bad cholesterol and raise good cholesterol, which functions to sweep away excess cholesterol. Research shows that fatty avocados, pulses (beans and lentils), almonds, and walnuts are especially good at lowering bad cholesterol.
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Myth #3: Eating fat makes you gain weight.
The truth: If you eat too many carbs or too much protein, you’ll gain weight, and the same is true of fat. But fat in and of itself (especially healthy fat) doesn’t make you gain weight. In fact, a JAMA study found no significant difference in weight lost or gained between people who followed a healthy low-carb diet and those who followed a healthy low-fat diet. Here’s why: While fat has more than twice as many calories per gram as either protein or carbs, it also provides increased satiety, says Sandy Procter, Ph.D., a registered dietitian and an assistant professor emerita in Kansas State University’s Department of Food, Nutrition, Dietetics, and Health. “Fats digest more slowly than foods that are fat-free and allow us to feel fuller longer after we eat,” Procter says. In short, while fat has more calories pound for pound, you need to eat less of it to feel satisfied.
Myth #4: Low-fat or nonfat products are healthier.
The truth: Not if a product’s fat was replaced with sky-high amounts of sugar, which is often how fat-reduced processed foods are made palatable. Refined carbs and added sugars (sugars that don’t occur naturally in a food) can decrease insulin sensitivity and raise both your blood pressure and your blood triglycerides, a type of fat that circulates in the blood, says Taylor Wallace, Ph.D., principal and CEO at the Think Healthy Group and an adjunct professor in the Department of Nutrition and Food Studies at George Mason University. Those are all risks for heart disease. When considering a lower-fat option, read the nutrition label and check for added sugar. The Dietary Guidelines for Americans recommends limiting added sugar to 10% or less of your calories a day.
Myth #5: All plant-based fats are healthy.
The truth: Alas, not so. Many are, but the idea that if a fat comes from a plant it’s automatically good for you is incorrect. Tropical oils like palm oil, palm kernel oil, and coconut oil, for example, are very high in saturated fat. Coconut oil is 83% sat fat, which is higher than butter (63%) or bacon grease (39%). “Coconut oil is one of the worst fats you can use,” Wallace says. Tropical oils, which frequently pop up in vegetarian and vegan products, significantly raise bad cholesterol. Stick with olive oil or perilla oil, which contains alpha-linolenic acid, an omega-3 fatty acid that, in clinical trials, was found to decrease heart disease risk, says Steven Gundry, M.D., director of the International Heart and Lung Institute and Center for Restorative Medicine. Olive oil, he adds, “is loaded with polyphenols, plant compounds that are absolutely, positively heart- and brain-healthy.”
Kate Rockwood is a freelance writer based in New York.
