Good Fats, Bad Fats & the Omega Fatty Acids


Not all fats are the same and as a successful LCHF practitioner you should have a basic understanding of the kinds of dietary fats that are out there and what they mean for your health. 

I consider this one of the most important parts of your LCHF knowledge.


As discussed, fats or more specifically fatty acids are essential for humans. Fats can generally be classified as saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA). Further, PUFAs contain 2 essential classes of fatty acids called Omega 6 and Omega 3 . These are associated with healthy cell membranes. Dietary sources of fats will generally contain a mixture of all three types, depending on their source e.g. coconut oil is 2% PUFA, 6% MUFA & 92% SFA whereas something like sunflower oil is 69% PUFA, 20% MUFA & 11%SFA. So in dietary terms, of these 3, what do we consider to be “good” and “bad” fats?

PUFAs: Omega 3 & Omega 6 fatty acids

To answer this question we need to look in more detail at PUFAs, in particular the omega 3 & 6 fatty acids. It turns out that the ratio of omega 3 to 6 fatty acids is critical, with overall requirements in humans being relatively small. Omega 3 fatty acids are associated with a reduction in inflammation whereas large amounts of omega 6 fatty acids are associated with an increase in inflammation. Further, high omega 6 intake adversely affects omega 3 metabolism, further worsening the situation. Most modern western diets are very high in omega 6 and very low in omega 3 fats, the exact opposite of what they should be. This is mainly due to the fact that high-PUFA fats are cheap and widely used in the fast food market e.g. soy, corn, cottonseed, peanut, sunflower, and safflower oils. Note: with the exception of peanut oil, these are all vegetable oils.

So what’s the trick in ensuring you get enough omega 3 and less omega 6? For the LCHF practitioner whose diet is already 70%+ fat it’s really quite simple; just stay away from those fats with relatively high levels of PUFA and stick to those with higher levels of SFA and MUFA i.e. drop the vegetable fats in favour of the animal fats, in particular fatty fish such as salmon which are high in omega 3.  That means avoiding all of the above plus margarine and mayonnaise made from any of the above. You will also know if you are consuming too much omega 6 because you will feel unwell. It’s one of the common pitfalls of LCHF when starting out i.e. consuming high amounts of vegetable oils in place of saturated animal fats. If you still suspect that you aren’t getting enough omega 3 you can always try supplementing with omega 3 capsules, etc.

Below is a useful chart of most of the major dietary fats and oils, together with their relative proportions of SFA, MUFAs & PUFAs. This is taken from “The Art and Science of Low Carbohydrate Performance by Stephen D. Phinney & Jeff S. Volek”, see resources page. It’s worth printing this out and sticking it on your fridge door until things settle down and it becomes second nature to you.


Here is a further, more detailed list.

Rapeseed (canola) oil

At this point I would like to talk about my experience with rapeseed or canola oil. On the face of it, rapeseed oil would appear to fit the bill perfectly as far as omega 3/6 fats are concerned: 28% PUFA, 64% MUFA & 7% SFA. I started incorporating it into my diet in the form of homemade mayonnaise around 6-8 months ago. All was fine until the spring of this year when I noticed a small, unaccountable, yet steady increase in my weight. Further, once the hay fever season started, around May of this year, I noticed that on occasions I would suddenly start sneezing and my eyes would water for no apparent reason. This was similar to my experiences with dairy, in particular feta cheese which produced exactly  the same reaction as soon as it hit my stomach. Alarm bells started ringing, something was inflaming me! This time it wasn’t difficult to focus in on the exact cause, namely the rapeseed oil in the mayonnaise. Further research soon revealed that rapeseed oil is indeed inflammatory but NOT due to the omega 6 fatty acids as one might suspect. No, this time it was a different one, namely omega 9 or erucic acid which is damaging to cardiac muscle of animals. Not only that but the pollen contains known allergens and also, it wasn’t until not so long ago that it was used as a lubricant for steam engines! Wow, is this stuff really fit for human consumption?!? Not in my opinion!

Naturally, I immediately dropped the rapeseed oil in the mayonnaise and replaced it with light olive oil. Bingo! My weight started to fall again, and all hay-fever-like symptoms also completely vanished. Hence, it goes without saying that I DO NOT recommend the consumption of rapeseed oil by humans, despite what any food agencies or anyone else might say!


With the exception of my rapeseed oil experience, I think I am getting things about right as far as intake of omega 3 & 6 are concerned. Indeed I have all the correct symptoms associated with adequate omega 3 intake: smooth healthy skin with no dry patches, improved eyesight, improved cognition, etc, etc., without having to really think about it, which is great.

Note: The only way to be absolutely sure that you are receiving adequate quantities of omega 3 & 6 in the correct proportions is to have a blood or cheek cell test, something that I’m going to do as soon as I can find somewhere properly equipped to do so!

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