Fat is the bane of many diets, but it's an essential macronutrient—it's no less mandatory than the protein we need to eat. It plays a variety of functions in the body. It's a source of energy alongside the glucose we get from carbohydrates. Fats help us absorb the vitamins we take and allow our cells to communicate with each other. And, yes, they help food taste good, too.
“If you appreciate the smoothness of guacamole or the flakiness of a croissant, you have dietary fats to thank,” says Ali Webster, a registered dietitian and senior director of research and nutrition communications at the International Food Information Council.
Naturally, like other elements to a complete diet, fats should be enjoyed in moderation. That’s because fats are also high in calories: Every gram of fat contains nine calories, while every gram of protein or carb you eat contains only four. For that reason alone, fats can be detrimental for maintaining a healthy weight and heart. But they’re in lots of the foods we’re all eating: meat, fish, milk, and more. So let’s chew the fat, and break down what’s important to know.
Cut the Fat
There are two types of dietary fats, both of which are composed of long, straight chains of carbon atoms, with a varying number of hydrogen atoms running along the length of the chain. Saturated fats are called that because they have more hydrogen atoms—which also means they’re solid at room temperature. Unsaturated fats have fewer hydrogen atoms, and are usually in liquid at room temperature.
Saturated fats are found in animal foods, like chicken and beef, as well as in the types of foods everyone loves to eat: pizza, foods, desserts, and drive-thru cheeseburgers. These are the fats that can lead to higher levels of LDL, or low-density lipoprotein. As you know from GQ’s primer on cholesterol, LDL is the bad stuff, too much of which can clog up our blood vessels and make it difficult for the body to adequately move oxygen around. The Dietary Guidelines for Americans recommend a saturated fat intake of less than 10% of someone’s daily calories. The American Heart Association goes a little further: No more than 6% of your daily calories should come from saturated fats.
Not That Kind of Poly
The real problem, with fat, is that people don’t eat enough unsaturated fats, at least according to the Harvard School of Public Health. Unsaturated fats are broken into two groups: monounsaturated and polyunsaturated. Avocados, almonds, and olive oil contain monounsaturated fats; salmon, walnuts, and canola oil contain polyunsaturated fats.
As Webster points out, there are observational studies that indicate replacing saturated fats with monounsaturated fats can lead to a better balance of LDL and HDL—high-density lipoprotein, or the good cholesterol—and therefore improve the function of blood vessels in the body. Better function means better cardiovascular health. Meanwhile, polyunsaturated fats help to reduce the total amount of LDL cholesterol, thanks to their concentrations of omega-3 and omega-6 fatty acids.
Omega-6 fatty acids are found in many seed oils, and while these fatty acids (and seed oils) don't seem to be harmful unto themselves, they certainly can be if you’re consuming too much, which is easy to do if you're eating lots of industrial processed foods. The body works best when it’s running on more omega-3 fatty acids. Packed with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), omega-3 fatty acids are associated with several good health outcomes: lower risk of premature death among older adults, according to Harvard research; lower blood pressure; and better overall heart health. For this reason, the American Heart Association recommends eating at least 10% of your daily caloric intake in the form of polyunsaturated fats rich in omega-3s. Salmon is your friend here, as are walnuts, canola oil, and mackerel.
Beware Trans Fats
We’ve covered saturated and unsaturated. Now comes the dreaded trans fat, the one fat you’ve undoubtedly been told numerous times (including by us) to avoid. Technically, trans fats are unsaturated fats, but behave more like saturated fats.
“Evidence is resoundingly clear that trans fats are associated with coronary heart disease,” Webster says. “This is why it’s recommended that we consume as few trans fats as possible.”
Trans fats raise LDL and lower HDL, and they also create bodily inflammation, a singular source of many health problems. So what the hell are they? If you’ve heard the phrase “partially hydrogenated oils,” you’re somewhat familiar with trans fat. Those oils are the stuff that helps fry food. There are small quantities of trans fats found in meat and dairy, but they’re primarily found in processed foods and baked goods.
As usual, understanding the nutritional nitty-gritty is less illuminating than the overall lesson that it's helpful to avoid processed foods. And no one’s saying stop eating cookies. Just don’t eat the whole sleeve of chocolate chips. And maybe eat fish for dinner beforehand. Still confused? Check out this visual guide to good and bad fats.
