Let’s Talk About Fats

Hannah O’Shei


February 22, 2021
Share on email
Share on facebook
Share on linkedin
Share on google
Share on pinterest
Share on whatsapp
Share on twitter

Low fat diets seem to be all the rage these days but the recommendation to eat a low-fat diet has been around for about 40 years. According to Harvard T.H. Chan School of Public Health nutrition expert David Ludwig, low-fat diets are “deeply embedded in public consciousness and food policy.” However, the majority of evidence tells us that eating a low-fat diet doesn’t equate to being healthier or having less body fat. The truth is fat is an essential part of our diet. Fat is needed for energy, cell growth, the nervous system, hormone production, and the absorption of fat-soluble vitamins (3).

At this point many of us know that we should focus on eating more “healthy fats” like monounsaturated and polyunsaturated fats and less “bad fats” like saturated and trans fats. But what’s the difference?

Let’s explore types of fats and talk about their role in the human diet.

Polyunsaturated & Monounsaturated Fats

Polyunsaturated and monounsaturated fats are beneficial for health in many ways. These fats remain liquid at room temperature (think olive oil)(3). Eating more of these fats can help reduce “bad” LDL cholesterol; high LDL cholesterol puts you at risk of heart disease and stroke. They also help to increase “good” HDL cholesterol which lowers your risk for heart disease and stroke (3). 

Monounsaturated fat is found in nuts, avocado, canola oil, olive oil, safflower oil, peanut oil, peanut butter, and sesame oil (5). Polyunsaturated fat is found in walnuts, sunflower seeds, flax seeds, flax oil, fatty fish, corn oil, soybean oil, safflower oil, and microalgae (generally consumed as a supplement) (4). Many foods such as nuts and plant oils contain a mix of monounsaturated and polyunsaturated fats.

More About Polyunsaturated Fats

When it comes to polyunsaturated fats there are two main types, both of which are essential meaning we need to get them from our diet: Omega-3 fatty acids and Omega-6 fatty acids (3). Omega-3 fatty acids can help reduce triglycerides (fat in the blood), reduce risk of heart problems, slow the buildup of plaque in our arteries, and lower blood pressure. Omega-6 fatty acids can help control blood sugar, reduce risk for diabetes, and also lower blood pressure. We also need these fats for proper brain function and cell development (4).

Saturated Fats

Saturated fats may be harmful if they are replacing polyunsaturated and monounsaturated fats in the diet. Saturated fats are solid at room temperature (think butter and lard). Foods that are higher in saturated fats are meats, whole dairy products, cheese, coconut oil, and processed foods (4). The most current evidence suggests that replacing saturated fats with healthy fats in the diet can help lower “bad” LDL cholesterol and can raise “good” HDL cholesterol which is beneficial for the heart. Saturated fats do not need to be avoided entirely though, and can still be a part of a healthy and balanced diet (3).

Trans Fats

Trans fats are made through a process called hydrogenation. Trans fats raise “bad” LDL cholesterol and lower “good” HDL cholesterol; they also cause inflammation, increase insulin resistance, and increase risk of heart disease. Trans fats have actually been banned in the U.S as a result of their detrimental health effects (3).

The Takeaway

Dietary fat is an essential macronutrient and while it’s important to eat more unsaturated fats than saturated fats both can be part of a healthy and balanced diet. The 2015-2020 Dietary Guidelines for Americans recommend that no more than 10% of total daily calories come from saturated fat and total fat consumption should not exceed 25-30% of daily calories (4,5). Below I have listed some fun swaps to help replace unhealthy fats in the diet with healthier ones.

  • Instead of red meat for dinner try fatty fish like salmon
  • Replace butter with olive oil
  • Add nuts and seeds to salads, smoothies, and oatmeal
  • Cook with plant oils rather than solid fats like butter and coconut oil
  • Try avocado instead of mayonnaise on sandwiches
  • Sprinkle ground flax seeds, chia seeds, or hemp hearts on meals


  1. https://www.hsph.harvard.edu/news/hsph-in-the-news/low-fat-diets-failed-experiment/
  2. https://www.hsph.harvard.edu/news/press-releases/low-fat-diet-not-most-effective-in-long-term-weight-loss/ 
  3. https://www.health.harvard.edu/staying-healthy/the-truth-about-fats-bad-and-good 
  4. https://medlineplus.gov/ency/patientinstructions/000747.htm
  5. https://medlineplus.gov/ency/patientinstructions/000785.htm

Edited by PreRD intern, Lauren Gatto

Hannah O'Shei

Hannah O'Shei

Hello! My name is Hannah O’Shei and I’m a senior dietetics major at the University of Massachusetts, Amherst. Some of my nutrition interests include community and public health nutrition, plant-based nutrition, and intuitive eating. I would love to work in a community or public health role and one day I am interested in opening a private practice with a focus on plant-based and vegan nutrition. In my free time I enjoy hiking, cooking and baking, going to farmer’s markets, and having fun with my fiancée and our three-year-old daughter.