trans fats

You’ve probably heard about the infamous trans fats (trans-fatty acids), and how you should try to avoid them. Trans fats still pose a public health problem, even though awareness of trans fats has increased, regulators have restricted use, and overall intake of trans fats has declined.

So, what are these fats and what are the health implications? What are the best healthy fats to consume on the ketogenic diet?

What are Trans Fats?

Trans fats are a type of unsaturated fat. Unsaturated fatty acids contain one or more double bonds (i.e. not fully saturated with hydrogens), whereas saturated fats only contain single bonds (i.e. the carbons are fully saturated with hydrogens). Double bonds can be figured as either a cis isomer (longest chains or heaviest elements are across from one another) or as a trans isomer (longest chains or heaviest elements are diagonal or opposite to one another). Trans fatty acids have a kink in their structure due to the arrangement of their bonds.

Trans fats can occur in nature, but are the ones most associated with health risks are artificial, industrial, or partially hydrogenated fats. Most trans fats are made through the industrial process where hydrogen is added to vegetable oil. 

fatty acids trans fats

Trans fats are often created from vegetable oils that chemically altered in the manufacturing process to ensure they stay solid at room temperature and to give them a longer shelf life. For that reason, these oils are more appealing to many food manufacturers, but they’re not a good choice for human health. Some restaurants use partially hydrogenated vegetable oil in their deep fryers, so they don’t have to change the oil as often as they do with other oils [1,2].

This manufactured form of trans fat is typically found in various food products that are commercial, fried, fast, processed, refined, and packaged. Foods that usually contain these fatty acids include:

  • Shortening
  • Microwave popcorn
  • Baked goods like cookies, cakes, and pies
  • Fried foods, such as fried chicken
  • Non-dairy coffee creamers
  • Margarine


What are the Possible Health Implications?

While food manufacturers now face some restrictions on trans fatty acids, unfortunately, they’re still widely available, used, and consumed.

As previously mentioned, trans-fatty acids are arranged in such a way that there is a kink or bend in the chain (since the two longest chains are on opposite sides from one other). This structure makes these fatty acids more susceptible to build up and cause atherosclerosis (build-up of plaques in the arteries, aka clogged arteries).

Research shows that these fats might negatively affect cholesterol levels and increase the risk of heart disease, heart attack, stroke, blood vessel disease, and type 2 diabetes [3,4,5,6,7,8].

Large amounts of trans fats can harm glucose and insulin function. A diet high in trans fats is also associated with insulin resistance and elevated belly fat. Studies also indicate trans fats can increase inflammatory markers in the body, particularly in people who are obese or overweight [9].


How Can You Avoid Trans Fats on Keto?

Most foods that contain trans fats or high amounts of trans fatty acids aren’t suitable for a ketogenic diet anyway. On keto, it’s best to choose more natural whole foods and limit your intake of packaged and processed foods, even if they’re organic and you know they don’t contain any trans fats.

If you’re choosing packaged products, find ones that don’t have trans fats on the label. It’s important to remember that in the United States today if a food has less than 0.5 grams of trans fats in a serving, the label for that food can read 0 grams of trans fat. You can also look for the words ‘partially hydrogenated’ on the ingredients list.

If you’re eating at a restaurant and you’re unsure if they use partially hydrogenated vegetable oils for frying and cooking, just ask your server or call the restaurant before you go. At home, don’t use vegetable oils and fill your pantry with healthier cooking oils, such as coconut oil, ghee, and duck fat. For sautéing or cooking at lower temperatures you can use olive oil.

Read our informative guide on sourcing healthy fats on keto.


How Do You Avoid Trans Fatty Acids and What are Your Favorite Healthy Fats?

How do you choose the healthiest fats on the ketogenic diet?



1) Mayo Clinic. Transfat is Double Trouble for Your Heart Health.

2) U.S. National Library of Medicine. Facts About TransFats.

3) Clarke, R., & Lewington, S. (2006). Trans fatty acids and coronary heart disease. British Medical Journal, 333(7561). doi: 10.1136/bmj.333.7561.214

4) Sun, Q., Ma. J., Campos, H., Hankinson, S. E., Manson, J. E., Stampfer, M. J., Rexrode, K. M., Willett, W. C., & Hu, F. B. (2007). A prospective study of trans fatty acids in erythrocytes and risk of coronary heart disease. Circulation, 115(14). 1858-1865. doi: 10.1161/CIRCULATIONAHA.106.679985.

5) Oomen, C. M., Ocke, M. C., Feskens, E. J., Erp-Baart, M. A., Kok, F. J., & Kromhout, D. (2001). Association between trans fatty acid intake and 10-year risk of coronary heart disease in the Zutphen elderly study: A prospective population-based study. Lancet, 357(9258), 746-751. doi: 10.1016/s0140-6736(00)04166-0.

6) Ibrahim, A., Natrajan, S., & Ghafoorunissa, R. (2005). Dietary trans-fatty acids alter adipocyte plasma membrane fatty acid composition and insulin sensitivity in rats. Metabolism, 54(2), 240-246. doi: 10.1016/j.metabol.2004.08.019.

7) Natarajan, S., Ibrahim, A., & Ghafoorunissa. (2005). Dietary trans fatty acids alter diaphragm phospholipid fatty acid composition, triacylglycerol content and glucose transport in rats. British Journal of Nutrition, 93(6), 829-833. doi: 10.1079/BJN20051442.

8) Kavanagh, K., Jones, K. L., Sawyer, J., Kelley, K., Carr, J. J., Wagner, J. D., & Rudel, L. L. (2007). Trans fat diet induces abdominal obesity and changes in insulin sensitivity in monkeys. Obesity, 15(7). 1675-1684. doi: 10.1038/oby.2007.200.

9) Baer, D. J., Judd, J. T., Clevidence, B. A., & Tracy, R. P. (2004). Dietary fatty acids affect plasma markers of inflammation in healthy men fed controlled diets: A randomized crossover study. American Journal of Clinical Nutrition, 79(6), 969-973. doi: 10.1093/ajcn/79.6.969.


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