It’s hard to get rid of a bad reputation—something fat knows all too well. Dietary fats have been demonized for years, despite years of scientific research proving they’re really not that bad. In fact, you need fat in your diet. Not only does it make you feel full, but certain fats can also make you smarter, lower your risk for heart disease, improve blood vessel function, and even help control blood sugar levels.

With that in mind, let’s put these oft-repeated fat myths to rest—for good.

1. Myth: Low-fat diets are the healthiest.

Getting to the root of this myth isn’t as easy as pointing the finger at a marketing mogul who was out to vilify butter and steak.As early as the 1940s, scientists knew there was a correlation between high-fat diets and high cholesterol levels. So they began suggesting a low-fat diet for those at risk for heart disease. The idea caught on, and by the 60s, low fat was hip. But it was Senator George McGovern who really drove it home when he called a hearing that led to the first dietary guidelines for Americans.McGovern made some good points: He criticized the increase in soda consumption (which had surpassed milk as “the second most-consumed beverage”) and highlighted the decrease in the amount of fruits, veggies, and grains people were eating. As a solution, McGovern recommended that 55 to 60 percent of Americans’ caloric intake come from carbs. (That’s not far off from what the FDA advises today: 45 to 65 percent.) But somehow the takeaway became: Carbs are good; fat is bad.The problem with that is “when people look for low-fat products, they’re not necessarily the healthiest,” says Debbie Davis, R.D.N. “They may think they’re eating healthy because they’re having low-fat cookies, but they’re just eating refined sugar and carbohydrates.”One of the most damning studies against low-fat diets came out in 2006. The study looked at nearly 50,000 postmenopausal women over eight years and tallied up incidences of coronary heart disease, stroke, and cardiovascular disease. The findings were clear: Low-fat diets had no significant effect.Fast-forward another 10 years and the fat stigma is wearing off. Instead of low-fat, highly processed foods, Davis and other advocates often promote a Mediterranean diet that focuses on healthy fats from foods such as salmon, olive oil, and nuts, and minimizes “bad” fats from butter and red meat. (More on that below.)

2. Myth: All fats are created equal.

Even though all fats provide nine calories per gram, they’re not equal. Here’s a breakdown of the most common ones:Healthier FatsMonounsaturated Fats “Research has supported [that these fats] may decrease the risk of heart disease,” Gans says. Monounsaturated fats get all the love, partially because of a study from the 1960s that found people living in and around Greece weren’t dying of heart disease despite their high-fat diets. Researchers concluded it was because they were eating monounsaturated fats, and thus, the Mediterranean diet was born.Find them in: avocados; nuts; seeds; peanut butter; and lots of plant-based oils such as olive, peanut, canola, and sesamePolyunsaturated Fats These guys boast several of the same benefits as the mono kind. They can help improve cholesterol levels and potentially reduce your risk of heart disease. The kinds you hear about most are omega-6s and omega-3s, which help your body complete vital functions.Find them in: salmon, trout, soybeans, walnuts, tofu, and sunflower seedsNot-So-Healthy FatsSaturated Fats There’s conflicting science, but limiting the amount of saturated fat in your diet is best. “It’s very controversial right now,” Gans says. “But saturated fat is still associated with an increased risk for heart disease.”Diets high in these fats can raise total cholesterol levels. A small number of studies throw this into question, but many researchers aren’t convinced.Saturated fat, carbohydrates and cardiovascular disease. Kuipers RS, de Graaf DJ, Luxwolda MF. The Netherlands journal of medicine, 2012, Feb.;69(9):1872-9061. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Siri-Tarino PW, Sun Q, Hu FB. The American journal of clinical nutrition, 2010, Jan.;91(3):1938-3207. As Gans put it, “Even if something has a neutral effect, shouldn’t we go with something that has a beneficial effect instead?”Find them in: cheese, lamb, pork, coconut oil, butter, whole dairy products, and red meatTrans Fats After 2018, say good-bye to Twinkies, Thin Mints, and other 90s snack faves (at least as you remember them). The FDA has banned artificial trans fats, which are usually found in partially hydrogenated oils used in processed foods like the ones above. This type of fat has been linked to heart disease and high cholesterol, and has no known health benefits. But that doesn’t mean all trans fats will disappear. They also occur naturally in small amounts in certain meat and dairy products (think beef, lamb, and butter fat). But the jury’s still out on whether natural trans fat has the same cholesterol-raising effect as the artificial kind.Find them in: processed cookies, cakes, and crackers

3. Myth: All high-fat foods will raise your cholesterol.

Let’s start with the basics: Cholesterol is a waxy substance found in the fat in your blood that your body needs for certain cell functions. Decades ago docs linked high cholesterol to a number of health issues, including an increased risk for heart attack or stroke. That led to a lot of unnecessary fear about foods that contain cholesterol (eggs, for example).Today we understand it doesn’t really work like that.Dietary cholesterol, atherosclerosis and coronary heart disease. Kratz M. Handbook of experimental pharmacology, 2006, Apr.;(170):0171-2004. Cholesterol has a lot more to do with the kinds of fat (and carbs) you eat, as well as genetics. Saturated and trans fats have been known to raise cholesterol levels, so it’s important to limit your daily caloric intake from saturated fats to less than 10 percent—and avoid trans fats entirely.Unsaturated fats, on the other hand, may actually help lower your blood cholesterol levels. High-fat foods that contain monounsaturated fats (avocados; olive oil; salmon; sardines; and nuts such as peanuts, almonds, and walnuts) can be part of a healthy diet, even for someone watching their cholesterol. A handful of nuts per day—just about any type of tree nut will do—can also help keep your blood vessels healthy and reduce your risk of heart disease.

4. Myth: Eating fat will make you fat.

As we mentioned earlier, fat helps with satiety, so there’s a good chance that if you eat a meal rich in healthy fats—think salmon or an avocado and egg breakfast—you’ll feel fuller faster (and longer) and won’t overeat.Then again, if you know you’re prone to finishing an entire jar of cashews in one sitting, you should probably pace yourself. “In general, fat is higher in calories than carbs or protein,” Davis says. “So if you’re eating a lot of fat, you can go over your calorie needs.”Gans offers the same warning. “If you’re not measuring olive oil and you’re just adding a lot, you’ve suddenly added a lot of extra calories to your day,” she says.Bottom line: Fat—especially the monounsaturated and polyunsaturated kind—is part of a healthy diet. And if you stick to it in moderation (around 20 to 35 percent of your daily caloric intake, or 44 and 78 grams per day depending on your needs), it won’t make you fat.

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