Here's what's healthy and what's not.
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Eating fat makes you fat, right? If this is what you think, you're wrong. But it's not your fault -- it's probably what you were led to believe.

Actually, unsaturated fats, like those found in plant-based oils, nuts and fatty fish, are good for you because they help protect you from heart disease, help you maintain a healthy weight and even have some superficial benefits for your skin and hair.

But there’s a lot of confusion out there about the role dietary fat plays in our lives, and it's no wonder we're mixed up about it.

The History

Starting around 1980, top nutrition experts and the federal government advised all Americans to dramatically cut back on dietary fat to avoid heart disease and weight gain.

Back in the day, notes NPR, these experts wanted us to replace dietary fats -- from olive oil to butter to nuts -- with healthy carbohydrates, like whole grains, vegetables and fruits. This was based on well-meaning but misleading research that showed a correlation between diets high in fat and people with high cholesterol levels in their blood.

But of course, people didn't really replace big, juicy steaks with more vegetables. Instead, food companies co-opted this "low fat" message, creating high-sugar, low-nutrient snacks and foods that technically fit the low-fat bill but were anything but healthy. Anyone who recalls chowing down on Snackwell's fat-free Devil's Food Cookie Cakes will remember this era.

The Message Today

Now, more than three decades later, Americans are heavier and have more heart disease than ever before, and researchers suspect that when we replaced that fat in our diets with sugar and refined starch, it led to increased obesity and metabolic diseases like Type 2 diabetes. Both of these conditions can increase the risk for cardiovascular disease.

"Actually, farmers have known for thousands of years that you can make animals fat by feeding them grains, as long as you don't let them run around too much, and it turns out that applies to humans," said Harvard University food researcher Walter Willett in a past interview with PBS. "We can very easily get fat from eating too many carbohydrates, and the public was really directed to only focus on fat calories, when we really have to keep an eye on calories no matter where they're coming from."

Today, health experts and the federal government are trying to recalibrate the needle on dietary fat. With more complete, rigorously-conducted research about how unsaturated fats (like mono- and polyunsaturated fats) can actually protect people from heart disease, the nation's top nutritionists want to make sure that blanket, low-fat diet advice for the general audience is a thing of the past.

How Fats Work

One thing we do know now: Dietary fat isn’t evil, it’s simply a highly-concentrated source of calories that helps your body absorb essential vitamins like A, D, E and K. Fat helps keep your hair strong and glossy and your skin clear and youthful-looking. And contrary to what we’ve thought in the past, moderate amounts of healthy dietary fat can actually improve cardiovascular health, not harm it. Finally, for people who are trying to lose weight, foods with these fats can also help keep them satisfied for longer, which means they can eat less food to feel full.

Polyunsaturated fats, which are found in fatty fish like salmon and trout, as well as sunflower oil, walnuts and sunflower seeds, help reduce levels of LDL cholesterol in the body, which can help lower the risk of heart disease and stroke. Nutritionists refer to polyunsaturated fats (omega-6 and omega-3 fatty acids) as essential fatty acids, because your body needs them to function and can't produce them on its own. Monounsaturated fat, which is found in olive oil, avocados, peanut butter, nuts and seeds, can also have a similar effect on your body.

In light of all this new research about the role healthy fats play in our bodies, the 2015 Dietary Guidelines, which are the U.S. government's food and nutrition recommendations through 2020, actually dispensed with a traditional upper limit on the amount of fat a person should eat every day. Instead of eating a low-fat diet, Americans should eat a low saturated fat diet, explained Harvard’s Frank Hu, who helped create the guidelines.

A good serving size of healthy oils is around five teaspoons or 27 grams per day for someone eating a 2,000 calorie diet, according to the dietary guidelines.

However, there are two kinds of fat that Americans should keep at bay. Saturated fat, which is mostly found in meat and dairy products, should make up no more than 10 percent of a person’s diet because of its “strong relationship” with cardiovascular disease risk, notes the guidelines. Replacing one percent of calories from saturated fat with polyunsaturated fat reduces the risk of coronary heart disease by two to three percent, said the researchers who helped create the guidelines.

And there is no generally safe level of trans fat, which found mostly in pre-packaged, frozen and canned baked goods, because of its association with cardiovascular disease risk. That's why the Food and Drug Administration is phasing out the ingredient in the U.S. food supply.

Whether you're trying to lose weight or help maintain a healthy weight, don't fear the fat. Use plant-based oils to make your foods more delicious, toss back a handful of nuts if you need a snack, and load up on rich, fatty foods like avocado and fish to give your body the nutrition it needs.

To get some ideas about some healthy sources of dietary fat, check out the list below. Are you missing out on healthy fats in your diet?

Half of an avocado contains nearly 15 grams of fat total, and almost 10 of those are monounsaturated (2 grams are polyunsaturated). Try it in place of mayo on your next sandwich.
Almonds (And Other Nuts)
Just about any nut can make for a healthy fat-filled snack, but almonds happen to be the lowest in calories. One ounce -- about 23 whole almonds -- contains just over 14 grams of fat, including nearly 9 grams monounsaturated and about 3.5 polyunsaturated.
Salmon (And Other Fatty Fish)
Salmon may be one of the most well-known fatty fish, but tuna, mackerel and sardines also offer a heart-healthy dose of fats.

If you're going to stick with the familiar, look for wild-caught salmon. A three-ounce serving of chinook (often the most expensive option, according to Eating Well), contains nearly 9 grams of fat, including nearly 4 grams monounsaturated and about 2.5 polyunsaturated. The milder coho salmon and the oilier sockeye both contain less, at around 5 total grams of fat, with nearly 2 grams each of mono- and polyunsaturated fat.
Olives (And Olive Oil)
Darwin Bell/Flickr
Mixing 10 large olives into your next salad will add about 5 grams of fat, 3.5 of which are monounsaturated and .4 of which are polyunsaturated.

Not an olive fan? The oil is an even more concentrated source of healthy fats -- just don't be too heavy-handed on your pour: A single tablespoon contains over 13 grams of fat, nearly 10 of which are monounsaturated and about 1.5 are polyunsaturated.
Flax (And Other Seeds)
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One tablespoon of whole flaxseed -- which you can toss into salads, soups, smoothies, yogurt and more -- contains just over 4 grams of fat, including nearly 1 gram monounsaturated and almost 3 grams polyunsaturated.

Flax seeds also contain anywhere from 75 to 800 times more lignans, a component of plants that act as antioxidants, than other plant foods, WebMD reported.

A tablespoon of sesame seeds contains about 1.5 grams of monounsaturated fat and 2 grams of polyunsaturated fat. And an ounce of pumpkin seeds pack about 2 grams of monounsaturated fat and 2.5 grams of polyunsaturated fat.
One large, whole egg has almost 5 grams of fat, including roughly 2 grams monounsaturated and about 1 polyunsaturated.

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