So what makes them so off-limits? Trans fats can increase levels of bad cholesterol (low-density lipoprotein, or LDL) in your blood, lower your levels of good cholesterol (high-density lipoprotein, or HDL), are pro-inflammatory, and are bad for your heart, says Moskovitz. She explains that the US government is trying to ban them, though they haven’t reached an agreement yet.
The good news is “they’re in fewer places now than ever,” says Smith, “but it’s still important to be aware of them.” The best way to be sure it’s not in your food is to check the ingredients list: If you see “hydrogenated” or “partially hydrogenated” anywhere, steer clear.
Saturated Fats = Not-So Bad
Like trans fats, saturated fats are generally solid at room temperature (with the exception of palm oil and coconut oil). They’re found mostly in fatty cuts of meat, butter, full-fat dairy, cheese, baked goods, candy, and fried and processed foods. “Saturated fat affects your blood cholesterol levels more than the actual cholesterol in your diet,” says Moskovitz. And high blood cholesterol, in turn, can clog your arteries, potentially even leading to a heart attack or stroke.
That said, the opinion on saturated fat is shifting. “Research has been finding that saturated fat is potentially less dangerous than we once thought,” says Smith. “It’s not so much saturated fat by itself, but saturated fat in concert with high-glycemic carbohydrates” that raises your cholesterol levels, she explains.
While more research needs to be done, for now experts say women should aim for the American Heart Association’s (AHA) current guidelines of no more than 7% of daily calories from saturated fat—in a 2,000-calorie diet, that’s about 16 grams of saturated fat or 140 calories. If you have high cholesterol or a history of heart disease in your family, aim for 5 to 6% (about 120 calories or 13 grams in a 2,000-calorie diet).
Keep in mind, there are better and worse places to get your quota. A cut of lean red sirloin steak has 6 grams of saturated fat but also offers other nutrients including iron, B vitamins, and protein, Moskovitz explains—while processed fatty foods just give you “bad with bad.”
Polyunsaturated Fats = Good
Polyunsaturated fats come in two varieties: omega-6 and omega-3. Both can help lower your bad (LDL) cholesterol levels and our bodies can’t manufacture them, meaning we must get them from the foods we eat. “But we hear a lot more about omega-3 than omega-6 because we naturally get a lot more of it in the American diet,” says Smith. While experts recommend a ratio of up to 5 times as many omega-6 fats as omega-3 fats, most Americans get 20 to 50 times as many omega-6 fats. So to ensure you’re getting the right balance, just aim to include more omega 3s in your diet, says Smith.
You’ll get most of your omega-6s from safflower, corn, sunflower, and soybean oils; margarine and some shortenings; mayo and some salad dressings; sunflower seeds; and even fast foods (which are sometimes cooked with these oils). Women should aim to get no more than 2% of daily calories from them, says Moskovitz—that’s about 6 grams a day in a 2,000-calorie diet, or about 2 tablespoons of margarine.
Omega-3 is found mostly in fatty salmon, walnuts, and flaxseeds, as well as albacore tuna, tofu, herring, and sardines. It’s been shown to help reduce inflammation and heart disease risk, boost memory and brain function, and help grow your baby (and especially your baby’s brain) if you’re expecting. It can also help lower levels of free-flowing fatty acids called triglycerides, which are linked to poor diet and have similar effects as cholesterol, says Moskovitz.
Monounsaturated Fats = Great
Monounsaturated fat, experts say, is an excellent plant-based source of fat in a healthy diet. You can get it in nuts (which also have a good dose of polyunsaturated fats, says Smith), seeds, avocado, and most veggie oils, including olive, peanut, safflower, sesame, flaxseed, grapeseed, and canola oils. Monounsaturated fat can not only help lower bad LDL cholesterol levels, it can also increase your good HDL cholesterol levels, Moskovitz says.
What Else Is Good About Fat?
Both healthy fats—monounsaturated and polyunsaturated—boast added benefits for your body. They can help you:
Absorb vitamins: Healthy fats help your body to absorb “fat soluble” vitamins A, D, E, and K. “If you have a salad with fat-free dressing and no nuts or oils, you’re not getting the full benefits,” says Moskovitz. “Adding a little avocado, olive oil, nuts, or even cheese can help you absorb as much of these nutrients as possible.”
Stay full: Fats take longer to break down in your stomach than carbs, says Moskovitz, so you can expect to feel fuller for a lot longer.
Avoid crashing: Fats help keep your blood sugar stable, preventing major spikes and crashes when you eat high-carb foods. If you have a slice of bread alone, your blood sugar could spike, says Moskovitz. But add a tablespoon of olive oil and it won’t, because the fat slows down the breakdown of carbs and sugars in your digestive tract—good for all of us, but especially if you have diabetes or otherwise need to watch your blood sugar, says Smith.
Control your appetite: In addition to keeping you full and preventing blood sugar spikes, fats add a lot of flavor to your food, which can help you to feel more satisfied.
Promote weight loss: Because healthy fats are filling and satisfying, they can help you eat less overall. “People don’t see that often,” says Smith. “They think if they eat fat, I’m going to get fat. But it’s satisfying and can reduce your calorie intake overall.”
So How Much Fat Should I Get in My Diet?
So is there a maximum—or a minimum—to how much healthy fat you should eat? While experts used to recommend getting no more than 30% of your calories from fat, “we’ve been veering away from that limit,” Moskovitz says. Still, be mindful that high-fat foods are also high-calorie, at 9 calories per gram (versus 4 calories in protein and carbs). So if you’re trying to lose weight, be aware of how your portions stack up. Moskovitz and Smith both suggest aiming to get at least 20% of your calories—about 60 grams per day on a 2,000-calorie diet—from omega-3s and monounsaturated fats.