Good vs. Bad Fats on a Keto Diet

Of all the nutrients in the world, fats have been vilified the most. But over the past couple of years, it seems that the stance on fat has changed quite a bit, both in scientific communities and the general public. And with the rising popularity of low-carb and ketogenic diets, we’re definitely seeing a more positive attitude towards fat as a nutrient. Sill, not all fat is created equal and you need to learn how to spot good vs bad fats when on a keto diet.

About Fat

Fat is one of the three macronutrients, the other two being carbohydrate and protein. Your body needs macronutrients in relatively large amounts, this the term macro. Different macronutrients serve different purposes in the body. When it comes to dietary fats, in particular, they serve as building blocks, vitamin carriers, a source of energy, and mediators of many physiological processes like hormone building and toxin removal.

There are many different types of fat, and all belong to one of the following four categories:

  • Saturated fats
  • Trans fats
  • Monounsaturated fats
  • Polyunsaturated fats

Furthermore, the fatty acids of which all fats are made of are classified into short, medium, and long chain. Another way we classify fats is into essential and non-essential. Essential fats being those your body needs to get from food and without which it cannot survive.

Which Fats Are Good?

Fats are generally classified into good and bad based on whether they raise LDL cholesterol and cause inflammation. That’s because both of these are considered risk factors for cardiovascular disease, especially coronary heart disease. With that taken into consideration, fats considered good on a keto diet include:

Omega-3 fatty acids

Omega-3s are a class of polyunsaturated fatty acids (PUFAs), which are essential for human health. Researchers believe that most of us are not getting enough high-quality omega-3s through our diets and that we should focus on boosting our intake of these important anti-inflammatory, LDL-lowering fats. You can get more omega-3s from:

  • Fatty fish
  • Fish oil
  • Microalgae
  • Flax seeds
  • Chia seeds
  • Walnuts

Monounsaturated fats

Monounsaturated fats (MUFAs) are not essential since the body can make them from essential fatty acids. MUFAs are proven to be beneficial for heart and metabolic health since they lower bad (LDL) cholesterol and raise good (HDL) cholesterol. Because the Mediterranean diet is rich in these fatty acids, they were linked to the longevity and low rate of CVD in populations eating this diet. Keto sources of MUFAs include:

  • Olive oil
  • Nuts and seeds
  • Avocados
  • Cacao

Which Fats Are Bad?

Fats that raise LDL cholesterol and lower HDL cholesterol are bad. Fats that may cause inflammation are also bad on a keto diet and need to be avoided. Fats that fit this unfavorable description include:

Trans fats

Also called trans-unsaturated fatty acids, trans fats are quite rare in nature but may be found in large amounts in some processed foods. They pack a double whammy for heart disease by both raising LDL and lowering HDL cholesterol as confirmed by clinical studies. They may increase your risk of having a heart attack by over 30%. Luckily, many countries are now adopting policies that ban trans fats altogether, but they may still be found in these foods:

  • Partially hydrogenated oils
  • Processed foods
  • Some stick margarines
  • Non-dairy creamers

Make sure to read the label when buying any heavily processed foods. Not all of them contain trans fats, but those that do will list it in the nutrition info or include partially hydrogenated oil on the ingredients.

Omega-6 fats

A big disclaimer: omega-6 fatty acids are not inherently bad; in fact, they’re an essential PUFA. What makes them bad is that we’re getting too much of them. Studies show that our diets have a high omega-3 to omega-6 ratio and this is causing low-grade inflammation and illness. That’s why it’s a good idea to lower your omega-6s while trying to boost your omega-3s intake. Foods high in omega-6 fats include:

  • Sunflower oil
  • Pumpkin seeds
  • Soybean oil
  • Corn
  • Eggs
  • Poultry

Since avoiding omega-6s is next to impossible, it’s much more practical to focus on boosting your omega-3 fatty acid intake to achieve a more favorable ratio of these two essential fats in your diet.

What About Saturated Fats?

Health authorities have recommended reducing saturated fat in particular for decades. This recommendation was based on the diet-heart hypothesis that emerged in the mid-20th century. This hypothesis claims that saturated fats raise total cholesterol, and this raises your risk of heart disease. However, researchers have been questioning this hypothesis lately, saying that avoiding foods containing these fats can do more harm than good.

Besides that, researchers are also acknowledging the fact that saturated fats come in different chain lengths, and that this plays a big part in how they affect health. Medium-chain saturated fats are better for metabolic health than longer-chain fats. They also have antimicrobial properties.

So, the question of saturated fats remains an open one. It’s worth noting that many foods containing these fats have beneficial nutrients and are important on a keto diet. All in all, it’s best to not avoid these fats since the evidence against them is poor. Sources of these fats include:

  • Red meat
  • Poultry
  • Pork
  • Dairy
  • Coconut oil
  • Palm oil

How to Eat Healthy Fats on Keto

Try to get more of your fats from minimally processed, real foods. Processed foods are generally high in trans fats and refined vegetable oils, which are bad for overall health. Instead, get most of your fat from organic animal products, nuts, seeds, cold-pressed oils, butter, and other real foods.

Also, try to boost your intake of omega-3s as much as possible since these are the most difficult to obtain on any diet. To eat a balance of healthy fats on a keto diet, make sure your diet is based on these foods: Nut products (flour, butter, etc.), olive oil, butter, fatty cuts of meat, full-fat dairy, coconut oil, and avocados.


Fat is an essential nutrient we absolutely need in our diet, especially if that diet is keto. But not all fats are created equal; some fats are better than others. When choosing the source of fat for your diet, make sure to pay attention to its quality by focusing on omega-3s and MUFAs and limiting trans fats. Saturated fats and omega-6 fats are also acceptable, as long as you are balancing out your intake with other fats.


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