Does “fat make you fat”? Historically, physicians and dietitians have encouraged patients to limit fat intake for the sake of their heart health and waistlines. The low-fat trend took root in the late 1980s. Since then, “low-fat” or “fat free” have been two front-of-package marketing terms used by food companies.
Sometimes these foods are naturally low in fat. But too often, making a product low-fat involves a lot of processing. Compare the ingredients in regular cream cheese vs fat-free cream cheese to see this played out. Recently, fat is back in fashion, and the health food industry is embracing fat as an essential part of a healthful diet.
Functions of healthy fats in your diet
- Fat helps your body absorb fat-soluble vitamins (A, D, E, and K)
- Fat carries fat-soluble vitamins through the body
- Essential fatty acids omega-3 and omega-6 can only come from the diet, and are necessary for many normal body functions
- Inflammation, blood clotting, and brain development are all controlled by fat
- Fat improves the health of hair, skin, nails, and strengthens the cell membranes of all tissues
- Fat makes up our long-term energy stores
So should I try to eat MORE fat?
Not exactly. As we know, too much of anything can have negative effects. Fats provide 9 calories per gram, while carbohydrates and protein have only 4. That means that foods high in fat are usually more calorically dense than others.
In my opinion, the biggest concern with too much fat is that you’re not eating enough variety. To ensure you don’t crowd out other nutrients, aim for 20-35% of your calories coming from fat.
However, not all fats are equal. You’ve probably heard of three types of fats: Saturated, Unsaturated, and Trans. Understanding the difference between the three can help you make the best choices for your health.
The story of trans fats looks a little like Taylor Swift’s song “Bad Blood.” Trans fats were wildly popular at first, but are now being put to shame by the US Food and Drug Administration. Food scientists were “thinking that [they] could be trusted” but it turns out that trans fats actually cause “bad blood”.
In other words, we should avoid trans fats all together. Read those labels carefully. Trans fats are made in a laboratory by adding hydrogen to the fat to make it more stable. Thus, foods that contain “hydrogenated” oils contain trans fats, even if the label says 0g.
Saturated fats are found mostly in animal sources, and should be limited to less than 7% of our total calories. What does that really mean? For a 2,000-calorie diet, less than 140 calories should come from saturated fat. That means about 15 grams of saturated fat.
But less isn’t always the goal. Saturated fat in the recommended amount is beneficial.
Saturated fat improves bone health by aiding in calcium absorption. It aids in the repair and functioning of the brain. Your brain is made up primarily of fat and cholesterol to begin with. Saturated fat promotes proper immune function by improving the ability of white blood cells to identify and fight off infection.
Additionally, saturated fats contain powerful compounds like lauric and myristic acid that are only otherwise found in a mother’s breast milk. For these and many other reasons, saturated fat is gaining a comeback from its bad name.
However, it is still important that we understand quality over quantity. Choose high-quality whole foods, not overly processed sources of saturated fat.
Unsaturated fats are found mostly in plant sources like nuts, seeds, olives and avocados; fatty fish being the exception. The plant-based sources do not contain cholesterol.
Unsaturated fats are a big category and include both monounsaturated and polyunsaturated fats. Within the polyunsaturated fats are the Omega-3 and Omega-6 essential fatty acids.
Monounsaturated fats have been proven to reduce LDL (bad cholesterol) and have a neutral effect on HDL (good cholesterol). They are found in nuts, seeds, avocados, and olive oil.
Polyunsaturated fats have been proven to reduce LDL and simultaneously increase HDL. They are found in salmon and other fatty fish, flax seeds, and certain vegetable oils.
Omega-3 and omega-6 are essential fatty acids. That means our bodies cannot make them, and we must get them through our diet.
Omega-3 fats are found in fatty fish (in the animal forms, EPA and DHA), and flaxseed, walnuts, and soybean oil (in the plant form ALA). We can convert ALA to EPA or DHA, but it’s not a very efficient process. While all omega-3 fats are good, aim for some from animal sources.
Omega-6 fatty acids are found in vegetable oils, nuts, whole wheat breads, and chicken. Most Americans have no problem consuming enough omega-6. However, most would benefit from focusing on incorporating more omega-3 sources into their diet.
The ratio of the two is important to provide the health benefits of anti-inflammation, brain development, and cardiovascular disease protection. Recommendations suggest 3:1 (omega-6 to omega-3) is a good ratio. Currently, the average American diet has a ratio of closer to 15:1.
Since the 1990s, the Mediterranean diet has become increasingly popular. This pattern of eating includes moderate fat intake by including high intake of fish, nuts, seeds, and olive oil. Additionally, the Mediterranean diet limits meats and saturated fat intake, and is the leading heart-healthy diet. Beyond dietary implications, those who historically practiced the Mediterranean diet were also very physically active and had lower levels of stress.
For more information about fats, and how to get the most out of incorporating them into your diet, I recommend the following resources:
Position Paper of the Academy of Nutrition and Dietetics: Dietary Fatty Acids for Healthy Adults
The Other Side of Saturated Fats: Health Benefits of a Fat Rich Diet