Not All Fats Are Created Equally

We have a natural tendency to avoid fats when we are on a diet. And there is a good reason for it, as they are exactly what we are trying to get rid of. However, when we talk about ‘fats’ we are actually referring to a large group of molecules with different biochemical and nutritional properties. And ingesting some types of fats is crucial to keep our bodies healthy.

Fats are also called triglycerides and one of their main features is that they are insoluble in water, which is probably the reason why they evolved into storage molecules: by displacing water, they can be accumulated without the extra weight of the water molecules. They are also quite energetically dense, with every gram of fat producing circa 9 kcal of energy, which is twice what carbs or proteins yield (see “Good Carbs vs Bad Carbs for Weight Loss” and ‘The Importance of Protein’ for more information on carbs and proteins respectively).

Triglycerides are formed by three fatty acids attached to a molecule of glycerol. While the glycerol, molecule has a fixed structure, the fatty acids can be of different types and lengths. You’ve probably heard of saturated and unsaturated fats. These terms refer to the types of fatty acids in the triglyceride molecule, with saturated fats having more hydrogen atoms in their structure than unsaturated fats.

Unsaturated fats are healthier than saturated fats. Two of them, the omega-3 and the omega-6 fatty acids, are “essential” for humans, meaning that our organism absolutely requires them but it is unable to produce them. And the consumption of diets rich in oleic acid, another unsaturated fat, has been linked to a lower incidence of insulin resistance. Common sources of unsaturated fats are fish and vegetable oils, walnuts, almonds, avocado, sardines or salmon (if you like avocado, check out the recipe to ‘Superfood guacamole‘).

However, there is a group of unsaturated fats that should be avoided: the trans fats. Trans fats are rarely found in nature, being instead a byproduct of industrial food processing. They can be found in things like fried fast food or margarine. Their consumption has been linked to a higher risk of coronary heart disease, with a study even showing that for every 2% of calories from trans fat that you eat, the risk of heart disease increases by a staggering 23%. This, together with the fact that trans fats have no known health benefits, has prompted the FDA to determine that by 2018 no processed food should contain trans fats.

And what about saturated fats? Saturated fats sit somewhere in between the unsaturated fats and the trans fats, being neither as healthy as the former nor as pernicious as the latter. They are naturally found in foods like red meat and full-fat dairy products. It is OK to have some, but experts recommend keeping them below 10% of the ingested calories a day.

So remember, next time you feel tempted to speak badly of fats, remember that not all fats are equal, and while some are a no-go others are perfectly healthy. Don’t make the just pay for the sinners!

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About Author

Hi, my name is Emilio Greenberg and I work on obesity research. I graduated in Biology and later did my Master's degree in Madrid, where I met Sarah ("How I've met Emilio"). I now hold a PhD in Molecular Biology and am Assistant Professor at the University, so I spend my time between the bench and the classroom. My research focuses on human metabolism, obesity and the influence of different diets in our health. I try to understand how our bodies process the food that we eat and how our eating habits influence our susceptibility to disease. We are currently living an epidemics of obesity that needs to be tackled. I hope that through this series of articles I can help you understand the crucial importance for your health of keeping a balanced diet. Because, as much as a cliché as it may sound, we truly “are what we eat”... continue reading


  1. Hello. I have been reading alot on the Internet about low carb, low fat, high fat and all is so confusing!
    I need to lose weight because i have a fatty liver and insulin resistance. My Doctor told me to exercise and follow a low fat diet to lose the weight. Everywhere i have read it says low fat or fat free foods have more sugar, which would not be good for my insulin resistance.
    So, i believe my best options for my condition, in addition to exercise, is to eat a clean eating balance diet with healthy fats, vegetables, fruits, and whole grains. What is your opinion on fruits and whole grains that have a low glycemic load? Would the low glycemic load foods help lower my insulin resistance, and the healthy lower fat food improve my fatty liver? Am i on the right track?
    Thank you

    • Hi Naty,

      Thanks for your message. First and very important I’m no Doctor so I can’t play like one in the internet. I also don’t know what type of diet you have, so I can only share with you the knowledge that I’ve learned by books I’ve read about this topic.
      That said let’s start.
      From what I’ve read and investigated the cause of fatty liver and insulin resistance is due to a high sugar diet. High sugar diets come from drinking high sugar beverages and sodas, eating too much processed food like candies, cereals, cookies etc. 71%% of the processed food available on the supermarkets contain sugar. There are products like tomate sauce, ketchup, salad dressing that you probably never suspect that had sugar and if you read the nutrition table you realize how much sugar they contain. There are even products that due to marketing campaigns are considered healthy, like yogurts where plain yogurt yes it’s healthy but most of the yogurts you can find on your supermarket is heavy loaded with sugar. Please read the nutrition facts of each product you have at home or at your supermarket. Added sugar is everywhere, be aware. So, when we eat a lot of sugar our body produces insulin that gets rid of the sugar from the bloodstream (because high sugar levels on the blood are fatal) and generates fat to store the excess of sugar in the blood. As we continue to eat more and more sugar, more fat is generated and more insulin is needed until a point that your body gets resistance to insulin and needs more insulin to have the job done. The solution is not to add eat more sugar, instead is to avoid added sugar at all cost. Fatty liver disease is mainly caused by high levels of refined fructose. Refined fructose is in most processed food, especially in high sugar beverages and sodas (coke, pepsi etc). I have made a video explaining how added sugar is converted into fat and you can watch it here

      My personal advice, please always talk to your doctor before following any advice: Avoid sugar beverages, sodas and alcohol. Avoid processed food. Give a try to intermittent fasting (skip breakfast, instead have a cup of tea or coffee without sugar). When you fast your insulin levels go down and you start to burn fat, this will greatly improve your insulin resistance and will help you to lose weight, this have been proven by different studies (you can watch a video about how fasting can help to cure diabetes type 2 which is caused bu insulin resistance due to a high sugar diet here I know fasting may sound too crazy but is been known for thousand of years to be the most effective way our body has to heal.

      Fruit: fruit contains fructose but it’s natural fructose. Refined fructose is treated the same way as ethanol (alcohol ) but natural fructose is healthy and your body loves it. Plus fruit contains fiber (processed food doesn’t have any fiber in it), vitamins and other important nutrients. In my opinion fruits are the best food we can eat.

      Grains: I would stay away from any refined grains or bread. Whole grains are a better option.

      So, and to finish. In my NON Medical Opinion, I would recommend you to avoid sugar beverages and processed food. You can check my No Sugar Diet challenge to get you motivated to get rid of sugar on your diet here. And than,I would start with intermittent fasting, skipping breakfast for example.

      Hope I’ve helped. All the luck.

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