This blog is all about how we can maintain optimal health using evolutionary principles, hence the name. As you may have noticed in the previous paragraph I put control in quotation marks, and this was for a very specific reason. The control diet in this experiment was a diet that supplied 7% of all energy in the form of soybean oil, of which over 50% was omega-6. However, the intervention diet, contained only 3% soybean oil, and 4% was LC-MUFAs, and almost NO omega-6's. However, for each diet it was only this 7% of energy that supplied by fatty acids. We can see a breakdown of the fatty acids in both diets in the following table.
All of the results are very interesting, however I would like to cover what we can learn about how these PUFAs affect our metabolism. The first, and possibly most important thing to note for many readers, is that the higher the PUFA diet caused more weight gain than the LC-MUFA diet and this additional weight gain is due entirely to an increase in fat accumulation. So these PUFAs directly lead to fat accumulation but how? Well, the rest of the study has some helpful hints for us as to what is going on metabolically.
PUFAs and Insulin Resistance
The two different diets had profound effects on the hormonal systems of our body, especially insulin and energy homeostasis.
Hmmm, the soybean oil diet causes an increase in plasma FFAs, glucose, and insulin?
Insulin resistance anyone?
We have higher levels of circulating glucose and FFAs so we ramp up insulin production to deal with them, but it looks like that has little effect on our bodies ability to deal with the increased circulating energy. This is textbook insulin resistance, and it looks like it is caused by the increase in PUFAs in the diet.
PUFAs and Fatty Acid Oxidation
When we eat fats we should see a corresponding increase in the amount of fats we are burning for fuel. We can measure how much is getting burned many different ways. One good way to determine if fat is being burned is to look at the expression levels of certain genes known to be vital to fat burning. While there are many to choose from (I even covered several of them in The Ketosis Posts) the authors of this article looked at lipoprotein lipase (lpl), PPAR-gamma, fatty acid translocase (CD36), and fatty acid transport protein. As we have seen before lpl causes the release of individual fatty acids from triglycerides, and PPAR-gamma is an important controller for fatty acid metabolism. CD36 and FATP are important for moving these fatty acids around inside our cells. So we can see that each of these genes needs to be present for effective fat metabolism.
So what does our high PUFA diet to the expression of these genes in adipose tissue? Well it decreases their expression of course!
If we aren't burning these fats we would expect them to end up either floating around our blood, or inside adipose tissue. We have already seen both of these in the table above, and in the increased fat mass of the PUFA fed mice. Not only do we see increased levels of these fats in adipose tissue and circulation, but we see increased levels of them in our liver. When we have excess forms of energy the we are unable to burn in their current state, we send them to the liver to get turned into a more usable form of energy that can then be burned. These fats are extremely hard to transform in this way, so our only hope is to keep them in the liver, until our adipose tissue will allow them to be sucked up for storage. This leads to energy excess of FFAs, and the myriad of complications.
PUFAs and Adipose Inflammation
Obesity is characterized by inflammation of the adipose tissue. One way we can measure inflammation is by looking at the gene expression of inflammatory molecules, known as cytokines, in a similar fashion to how we previously measured fatty acid metabolism. When the authors looked at the inflammatory gene expression in adipose tissue what do you think they found? That's right, the PUFA diet had a large increase in adipose inflammation. Here is the graph.
The high PUFA diet creates the perfect storm for obesity. It causes insulin resistance, decreases our ability to burn fats, and increases adipose inflammation, all three of which are known to be characteristic of obesity.
Stumbling upon this article at this time was very fortunate, as I had been thinking more and more about the role of PUFAs, specifically omega-6s, in our current health crisis. We have seen time and time again that it is tough to hang your hat on one thing for the cause of obesity/diabetes. I think PUFAs are a very important piece of the puzzle that has been neglected a bit so far, due to the discussion favoring carbs and fructose. We have seen a similar trend in consumption of industrial seed and vegetable oils with obesity, and this is clearly no coincidence.
Many people will just say that we need to get our omega-3/omega-6 ratio more in check, and I think this helps to show that in order to do that we can't just pound the fish oil or other supplements, we really just need to cut out the omega-6's.
I think this also ties in nicely to another thing that I see coming up all the time these days, energy excess. When we consume these high PUFA diets we have trouble not only metabolizing them, but as a result all the other fats that we consume. Limiting our PUFA intake should be a priority for everyone hoping to maintain good health.
Sometimes it's the most obvious things that add the most value. When I first started paying more attention to my diet, I focused on eliminating sugar, omega-6 and grains. I ate simple, self-prepared foods, cooking mostly with coconut oil, olive oil or butter. As I learned more, I got more sophisticated and added supplements and other "magic bullets". When I couldn't seem to resolve some insidious issues, I began to look more deeply. I realized just how difficult it is to truly avoid bad oils. For instance, I often eat lunch at my work cafeteria. I thought chinese food would be safe, but surely there's a ton of oil used in preparing the meat, and probably even the rice. Virtually any bakery product uses a poor oil choice. And it goes on and on. So, good article, it seems it more important we recognize what to avoid than what to supplement.
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