Polyunsaturated fats cause weight gain

PUFAs cause weight gain

You are probably thinking, “what’s she on about now?!!” Well I’ve just discovered that polyunsaturated fats cause weight gain and many other undesirable things!

It’s just amazing to me how these things are totally around out there, but they don’t sink into my brain until I am ready to listen to it.

I was doing some work with a Gelatin company who pointed me to a post written by Cheryl Frost – a figure competitor and now coach for other athletes. She was in favour of the gelatin which she now uses instead of protein powder – a whole other story – but while I was there I read some of her other blog posts.

Cheryl was a former low carb dieter. After doing this for a number of years, she found that it was increasingly less effective. In fact, over time it ruined her metabolism as well as the function of hormones and thyroid gland. So they were switching over to a new philosophy pioneered by Dr Ray Peat who is a biologist.

The point of this method is to support bodily processes to feed the cells adequately for optimal health of the organs, hormones, fast metabolism and preserve muscle mass while living and exercising.

And central to this whole philosophy is removing polyunsaturated fats from the diet because they cause weight gain as well as a number of other health issues.

Polyunsaturated fats are sometimes known as PUFAs

In the past polyunsaturated fats were praised as the best type of oil to be consuming. Saturated fat like butter, and coconut oil were shunned as heart damaging and bad for health. However the tide has completely switched around, with more recent research showing that PUFAs are actually highly unstable. They are easily affected by heat, light and oxygen and likely to be rancid before it gets anywhere near you. This causes untold damage to the cells in the body.

In fact two of the most troubling issues is that it may damage the cells ability to process sugars correctly which is thought to be a major cause of diabetes and is implicated in breast cancer!

Here is a list of other lovely things it does:-

  • damage the cells in the pancreas that produce insulin
  • linked to age pigment formation and liver spots on your skin
  • makes your skin more sensitive to sun damage
  • lowers your metabolism
  • impairs protein digestion
  • damages the thyroid
  • negatively impacts hormones
  • overburdens the liver affecting detoxification of the body
  • are inflammatory contributing to obesity, autoimmune disease, diabetes, metabolic syndrome, cardiovascular disease, fatty liver disease
  • raise blood pressure and cause hypertension
  • cause liver damage
  • bowel disease
  • rheumatoid arthritis
  • depression
  • and I’m sure if I kept looking I would find plenty more to add to this list!

Holy crap! We were worried that PUFAs cause weight gain, but it looks like the least of our worries.

I had realised saturated fats were not bad for some time. I eat butter and coconut oil but I don’t think it really registered how bad the unsaturated fats really were and the damage they do.

“So what are PUFAs in?”, I hear you asking??!!

Well nearly every processed food it seems and these:-

Nearly all oils

All grains

Nuts and seeds

Some fruit & vegetables

All fish oils including Omega 3!

The point is that you can’t avoid them all together.  The fact is the body needs a small amount but the idea is to minimise them as best you can. I have seen the number of 4 grams per day as the aim to keep at or below.

So in terms of what to choose, here are some guidelines:-


Here are the best ones lowest in PUFAs



Mono Unsaturated
Coconut 91g 6g 3g
Macadamia 10g 60g 4g
Palm 49g 37g 9g
Olive 14g 72g 14g
Avocado 12g 75g 15g

Source: https://en.wikipedia.org/wiki/Macadamia_oil

Nuts and seeds

Only shredded coconut and macadamias are the lowest in PUFAs.

Shelled nuts and seed are exposed to light, oxygen and more. So when they’re used in cooking and heated like almond flour in baking, then it’s all bad news.

Boo! This includes my favourite – peanut butter. (I do have a solution for this though – will reveal in a future blog post.)

Butter etc.

Recommendations are grass fed butter, ghee, tallow, and lard.


There are many reasons I eat only minimal grain. A quick look revealed that you are looking at about 1g of PUFAs for every 100g of grain. So it’s entirely up to you.


The recommendation is to eat fish if you want the fish oil and not to take the capsule. Unless the manufacturer is super meticulous, there is a high likelihood that it will be rancid too. The product’s age, the way it’s stored, how long it’s kept on the shelf etc all play a part. So your anti inflammatory Omega 3s could very well be highly inflammatory, if they are not super fresh.


Chicken, eggs and meat will be high in PUFAs unless they are grass fed. Which is why the Paleo crew insist on grass fed only.

So have a look at the products you eat and check the source of the oil in them. Things like potato chips, corn chips, pre-packaged dips, olives, sauces, biscuits, breads, pastries, spring rolls, cakes, pizza, most restaurant/café food etc. Safflower, sunflower, canola or soybean oil are in many foods. These are full of PUFAs. Flax and Hemp oil are two of the worst as well. Polyunsaturated fats are everywhere! The worst part is that so many claim polyunsaturated fats are healthy.

No wonder we are all confused.

There is more to Dr Ray Peat and his philosophies.  This is the most important one to change in your diet immediately. It will start the improvement to your thyroid, hormones and sugar metabolism in your body.

Awareness on the health trail,

Kristy x

NB: New book outlining the Ray Peat style diet for health and weight loss. A 7 day meal plan and information on how to measure your food easily without having to count calories. The Zen Beach Diet available here.

Zen Beach Diet

Here are some references for further reading.






2 thoughts on “Polyunsaturated fats cause weight gain

  1. Pam

    Very interesting Kristy and as you said yourself I have been aware that Poly Unsaturated Fatty Acids are not good for you but not to the extend of what your article references. I must read more of Dr Ray Peat’s work.

  2. slimbirdy Post author

    Hi Pam, yes Ray’s work is very interesting but it is difficult reading as well, very technical. I found it better to go find other blogs who follow his principles but explain it a little more easily. See how you go, it’s interesting stuff.

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