Unless you’ve been living in a nutrition science-shielding bubble, you know this story well: A few decades ago, a low-fat craze exploded in the food industry. Margarine became the go-to spread, low-fat cookies and muffins lined every shelf, skim milk became the drink of choice, and nuts and avocados were shunned as being sky-high in fat.
However, what this low-fat craze got wrong is that not all fats are created equal. For starters, the body does need dietary fats—which is why it’s one of the three necessary macronutrients (along with carbs and proteins). Dietary fats help provide energy to the body, support cell growth, improve nutrient absorption, and help produce certain hormones, according to the American Heart Association (AHA).
There are actually four main types of dietary fats, and their healthfulness exists on a spectrum. While some fats are associated with an increased risk of heart disease, other types of dietary fat may actually help *decrease* that risk.
Unsaturated Fats: The Healthiest Option
The two types of healthy fats are known as monounsaturated and polyunsaturated fats. There’s also omega-3 fatty acids, which are a subtype of polyunsaturated fat. These healthy fats lower LDL (bad) cholesterol and increase HDL (good) cholesterol, which reduce the risk of heart disease, according to the AHA.
Most heart-healthy fats come from plant foods, such as nuts, seeds, soy and soy products, nut butters, olives, avocado, and oils made from these foods (e.g., olive oil or walnut oil). You can also find omega-3 fatty acids in certain types of fish, such as salmon, mackerel, and sardines. Learn more sources of healthy fats here.
Saturated Fat: Limit This Dietary Fat
Saturated fat—in large quantities—can have the opposite effect on your health: They raise LDL cholesterol levels.
Foods high in saturated fats tend to be animal products, like beef, poultry, and full-fat dairy. The AHA recommends limiting saturated fat intake to just 5 to 6 percent of daily calories. For a typical 2,000-calorie diet, that amounts to just 13 grams of saturated fat (or 120 calories from saturated fat) a day.
Trans Fats: Avoid This Dietary Fat
The most harmful fat in your diet is trans fat. Food companies may add trans fat to products in order to increase shelf life and create and maintain a consistent texture (for example, in some “no-stir” peanut butter or canned frosting). Unfortunately, these fats both raise LDL cholesterol *and* lower HDL cholesterol; this increases your risk of heart disease, stroke, and type 2 diabetes.
Since 2006, all nutrition labels in the United States must now include a line for trans fat, but here’s the catch: If the product contains less than 0.5 grams per serving, the nutritional label can say it contains “0 g of trans fat.”
A smarter way to scan your food for unhealthy trans fat amounts: Check the ingredients label. Avoid ingredients such as “shortening” or “partially hydrogenated vegetable oil.” (As of November 2013, the U.S. Food and Drug Administration removed partially hydrogenated oils from the list of “Generally Recognized as Safe” [GRAS] ingredients.) Along with partially hydrogenated oil, here are more foods that nutritionists almost never eat.
Most sources of trans fats are in heavily processed foods, so a great way to avoid them is by buying fresh, minimally processed ingredients whenever possible.