Healthy Fats Explained: Which Fats to Eat and Which to Limit

Healthy fats are mostly unsaturated fats, the kind found in olive and canola oil, avocados, nuts, seeds and fatty fish like salmon and sardines. Your body needs fat to absorb certain vitamins, build cells and make hormones, and choosing these unsaturated sources in place of saturated fat is linked with better heart health. The main fats to limit are saturated fat and artificial trans fat.

Why your body needs fat

Fat isn’t the enemy. It:

• Helps you absorb vitamins A, D, E and K, which are fat-soluble.
• Forms part of every cell membrane.
• Supplies essential fatty acids your body can’t make on its own.
• Provides concentrated energy, at about 9 calories per gram.
• Adds flavor and helps meals feel satisfying.

The National Academies suggest adults get about 20% to 35% of their calories from fat. On a 2,000-calorie day, that’s roughly 44 to 78 grams.

The main types of fat

Most foods contain a mix. Olive oil is mostly monounsaturated with some saturated fat, while butter is mostly saturated with some unsaturated.

A closer look at omega-3s

There are three main omega-3s. ALA comes from plant foods like flaxseed, chia seeds, walnuts and canola oil. EPA and DHA come mainly from fatty fish and seafood, and from algae. Your body can convert a little ALA into EPA and DHA, but only a small amount, which is why seafood is such a valuable source.

The Dietary Guidelines suggest about 8 ounces of seafood a week for adults eating around 2,000 calories, and the American Heart Association recommends fish, especially fatty fish, about twice a week. If you’re pregnant, breastfeeding or feeding young children, the FDA publishes advice on choosing fish lower in mercury, and your doctor can help you apply it. If you don’t eat fish, ask your doctor or a dietitian whether an algae-based omega-3 makes sense for you.

Saturated fat in context

The Dietary Guidelines for Americans, 2020-2025, recommend keeping saturated fat below 10% of daily calories, about 22 grams on a 2,000-calorie diet. The American Heart Association suggests aiming lower for people who need to bring down their LDL cholesterol.

What replaces saturated fat matters. Swapping it for unsaturated fats from plant oils, nuts and fish is linked with lower heart disease risk. Swapping it for refined starches and sugars, as many old-style low-fat products did, doesn’t offer the same benefit.

The story on trans fat

Artificial trans fats come from partially hydrogenated oils, once common in stick margarine, shortening, fried foods and packaged baked goods. Because they raise LDL and lower HDL cholesterol, the FDA took action to remove partially hydrogenated oils from the US food supply. They’re now rare in US products, though it’s still worth scanning ingredient lists on imported or older items. Small amounts of trans fat also occur naturally in dairy and meat.

Easy swaps

• Cook with olive, canola or another plant oil instead of butter or lard most of the time.
• Top toast with mashed avocado or nut butter instead of butter.
• Snack on a handful of nuts or seeds rather than chips or pastries.
• Choose fish or beans in place of processed meats a few times a week.
• Whisk your own salad dressing from olive oil, vinegar or lemon, and herbs.
• Keep portions in mind: a tablespoon of any oil has about 120 calories, so a measured drizzle goes a long way.

Unsaturated fats are central to the Mediterranean diet, and keeping saturated fat in check is part of the heart-friendly DASH diet. To see how fat fits with protein and carbohydrates, read our guide to macros.

The bottom line

Healthy fats are mostly unsaturated fats from plant oils, nuts, seeds, avocados and fish. Aim for about 20% to 35% of your calories from fat, keep saturated fat under 10%, and avoid artificial trans fats. Small swaps, like cooking with olive or canola oil and eating fish twice a week, add up to a heart-friendly pattern.