It’s no secret that low-carbohydrate diets have enjoyed the spotlight for the last several years, but another nutrient-specific diet has been on the scene for even longer: low-fat. For decades, “eating fat makes you fat” was widely viewed as a dieting mantra, tied largely to the fact that fat provides more calories per gram (nine) compared to the other macronutrients, protein and carbohydrates (which each provide four calories per gram). Though the tides have shifted in recent years and fat isn’t feared like it once was, low-fat diets are still heavily associated with weight loss and dieting culture.

We’ve written about dietary fats on several occasions (and made this helpful video), but in this article, we’re taking a different approach: laying out exactly what your diet may be missing if you drastically cut back on fat.

What is Fat and Why Do We Need It?

Fats are an essential part of a healthy diet. They provide us with a major source of energy, help us absorb vitamins and facilitate communication between the cells in our body. Fats also contribute to our enjoyment of food by adding taste and texture, like the creaminess of ice cream or the flakiness of a pie crust.

The fats we eat can be either saturated or unsaturated. Polyunsaturated (PUFA), monounsaturated (MUFA) and trans fatty acids are all considered to be unsaturated fats, which means that they have a double bond in their structure that causes a “kink” in the chain. As a result, unsaturated fats tend to be liquid at room temperature (think olive or vegetable oils) because the fatty acids can’t pack as tightly together. Saturated fats are usually solid at room temperature because their fatty acids are able to pack tightly together. They’re found in foods like butter and other dairy products, fatty meats, coconut oils and palm oils. Trans fats are technically unsaturated, but they behave much like a saturated fat.

The National Academies of Science, Engineering and Medicine recommend consuming 20-35 percent of our daily calories from fat. The World Health Organization and the Dietary Guidelines for Americans recommend that less than 10 percent of daily calories come from saturated fats and that trans fat consumption should be kept as low as possible. Both are associated with increasing risk factors for heart disease, though trans fats may be the worst culprit because even small amounts are known to negatively impact cholesterol levels, increase inflammation and contribute to insulin resistance.

What Might I Miss Out on While Following a Low-Fat Diet?

• Fat-soluble vitamins. Dietary fat helps us absorb vitamins A, D, E and K from the foods we eat. These are the four fat-soluble vitamins, and each have their own essential functions in the body. Vitamin A is important for vision, immune health and reproduction. It’s found in foods like meat, fish and dairy products, as well as in fruits and vegetables in the form of “provitamin A” (of which beta-carotene is an example). Vitamin D is needed to enhance calcium absorption to maintain bone health, improve immunity, and transmit messages between our brain and our organ systems. Even though our bodies can make vitamin D through exposure to sunlight, many people might not make enough. Therefore, it’s important to consume it through foods like fatty fish and fortified dairy. Vitamin E is a powerful antioxidant found in seeds and nuts. Vitamin K is crucial for blood clotting. We can make some of the vitamin K that we need, and it’s also found in vegetable oils and dark leafy greens.
• Essential fatty acids. There are a few types of fats that are vital for maintaining optimal health that we can’t make ourselves – or we do so very inefficiently – so we need to get them through foods or dietary supplements. These include omega-3 fatty acids like alpha-linolenic acid (ALA), docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and omega-6 fatty acids like linoleic acid. ALA is found in foods like flaxseed, walnuts, canola oils and soybean oils. DHA and EPA are found in fatty fish and fish oil. These omega-3s lower plasma triglyceride levels, blood pressure and inflammation. DHA and EPA also increase HDL cholesterol (the “good” kind of cholesterol). All of these actions contribute to protecting against heart disease. DHA is also involved in development of the eyes and brains of young infants, so it’s important that pregnant women, lactating women and women who hope to become pregnant get at least 200-300 milligrams of DHA every day. Linoleic acid is found in vegetable oils like canola, corn, sunflower and soybean oils. It has been shown to lower LDL cholesterol (the “bad” kind of cholesterol) and blood triglyceride levels when compared with carbohydrates.
• A healthy relationship with food. Like we’ve said about diets that focus on one single nutrient, following a low-fat diet doesn’t automatically lay the groundwork for healthy habits in the long-term. Healthy habits include maintaining a consistent and healthy eating pattern, eating in moderation and consuming a wide variety of food from all food groups. Limiting a particular food group can set us up to feel dissatisfied and unhappy, which can lead to overdoing it at the next meal or snack or just “giving up” on diet and health goals altogether. If you’re interested in eating healthier, try making small changes over time without restricting specific nutrients or whole food groups.

Going low-fat might sound like a great way to cut calories and lose weight, but while doing so may be successful in the short-term, it’s not without dietary consequences. Rather than restricting fat, focus on getting the right types like those found in fish, canola oils and olive oils, nuts, seeds, fruits and vegetables. A well-rounded eating pattern can and should include a mix of all types of foods!