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 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 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 .
: 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: .) 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 , 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 against low-fat diets came out in 2006. The 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 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 nine calories per gram, they’re not equal. Here’s a breakdown of the most common ones:
“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 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.
: avocados; nuts; seeds; peanut butter; and lots of plant-based oils such as olive, peanut, canola, and sesame
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 , which help your body complete vital functions.
salmon, trout, soybeans, walnuts, tofu, and sunflower seeds
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."
high in these fats can total cholesterol levels. A small number of studies throw this into question, but many researchers aren't convinced. Kuipers RS, de Graaf DJ, Luxwolda MF. The Netherlands journal of medicine, 2012, Feb.;69(9):1872-9061. 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?”
cheese, lamb, pork, coconut oil, butter, whole dairy products, and red meat
After 2018, say good-bye to Twinkies, Thin Mints, and other 90s snack faves (at least as you remember them). has banned artificial trans fats, which are usually 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 .
But that doesn't mean all trans fats will disappear. They also 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: 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 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. Kratz M. Handbook of experimental pharmacology, 2006, Apr.;(170):0171-2004. has a lot more to do with the kinds of fat (and ) you eat, as well as genetics. Saturated and trans fats have been known to , so it's important to limit your daily caloric intake from saturated fats to less than —and avoid trans fats entirely.
Unsaturated fats, on the other hand, may actually help lower your blood cholesterol levels. 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 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 of your daily caloric intake, or per day depending on your needs), it won't make you fat.
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