Understanding Saturated, Unsaturated, and Trans Fats

Which Is the Good One?

types of fats

Illustration: Alison Czinkota. © The Spruce, 2019

Eating low-fat food doesn’t mean we should give up fat entirely, but we do need to educate ourselves about which fats should ideally be avoided and which ones are more heart-healthy. Let’s be clear: we need fat in our diet. As the most concentrated source of calories (nine calories per gram of fat compared with four calories per gram for protein and carbohydrates), it helps supply energy. Fat provides linoleic acid, an essential fatty acid for growth, healthy skin and metabolism. It also helps absorb fat-soluble vitamins ( A, D, E and K). And, face it, fat adds flavor and is satisfying, making us feel fuller, keeping hunger at bay.

Although all fats have the same amount of calories, some are more harmful than others: saturated fats and trans fats in particular.

Saturated Fats

These fats are derived from animal products such as meat, dairy, and eggs. But they are also found in some plant-based sources such as coconut, palm and palm kernel oils. These fats are solid at room temperature. Saturated fats directly raise total and LDL (bad) cholesterol levels. Conventional advice says to avoid them as much as possible. More recently, the scientific community has become more divided, noting that there are different kinds of saturated fats, some of which have at least a neutral effect on cholesterol.

Trans Fats or Hydrogenated Fats

Trans fats are actually unsaturated fats, but they can raise total and LDL (bad) cholesterol levels while also lowering HDL (good) cholesterol levels. Trans fats are used to extend the shelf life of processed foods, typically cookies, cakes, fries, and donuts. Any item that contains “hydrogenated oil” or “partially hydrogenated oil” likely contains trans fats. Hydrogenation is the chemical process that changes liquid oils into solid fats.

The good news is that the U.S. Food and Drug Administration no longer recognizes artificial trans fats, or partially hydrogenated oils, as generally safe. It required food companies to phase out trans fats in their products by 2018 or prove why they are safe to use in their foods.

Unsaturated Fats

Monounsaturated fats and polyunsaturated fats are two types of unsaturated fatty acids. They are derived from vegetables and plants.

  • Monounsaturated fats are liquid at room temperature but begin to solidify at cold temperatures. This type of fat is preferable to other types of fat and can be found in olives, olive oil, nuts, peanut oil, canola oil, and avocados. Some studies have shown that these kinds of fats can actually lower LDL (bad) cholesterol and maintain HDL (good) cholesterol.
  • Polyunsaturated fats are also liquid at room temperature. These are found in safflower, sesame, corn, cottonseed and soybean oils. This type of fat has also been shown to reduce levels of LDL cholesterol, but too much can also lower your HDL cholesterol.

Omega-3 Fatty Acids

These include an “essential” fatty acid, which means it's critical for our health but cannot be manufactured by our bodies. Good sources of omega-3 fatty acids include cold-water fish, flaxseed, chia seeds, soy, and walnuts. These fatty acids may reduce the risk of coronary heart disease and also boost our immune systems.

So read those food labels carefully and choose your fats wisely. And as a rule of thumb, liquid fats are better for you than solid fats.

Article Sources
The Spruce Eats uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. US National Library of Medicine. Facts about saturated fats. Updated April 23, 2018.

  2. US Food & Drug Administration. Final Determination Regarding Partially Hydrogenated Oils (Removing Trans Fat). May 18, 2018.

  3. Mayo Foundation for Medical Education and Research. MUFAs: Why should my diet include these fats?. Updated April 28, 2020.

  4. Siri-Tarino PW, Chiu S, Bergeron N, Krauss RM. Saturated Fats Versus Polyunsaturated Fats Versus Carbohydrates for Cardiovascular Disease Prevention and Treatment. Annu Rev Nutr. 2015;35:517-43.  doi:10.1146/annurev-nutr-071714-034449