Why you are designed to eat and burn fat…your big brain


I’ve just finished a couple of public lectures and had a big two page spread and a front page piece in the national newspaper about our work in low carb high fat eating. That’s prompted quite a few questions about how some people can eat carbs and not get sick.  

Here are a few of these questions:

“Why are some people and populations fine on higher carb diets?”  

“Why are you promoting a higher fat lower carb approach given many people (and sometimes populations) exist disease free eating higher carb diets?”

“Why do I put on weight so easily and others don’t?” 

“How does a low carb approach change things?”

These questions are very important and I think understanding the answers helps us understand the whole situation. My take is simplified into this:

Insulin is a hormone produced by the pancreas which helps move glucose into cells. It is essential for life.

Sometimes cells become resistant to insulin so it is harder to move the glucose onto those cells. This, no surprise, is called insulin resistance.  Insulin resistance is a normal and useful human condition, at least in our natural (ancestral) environment.

Humans very easily develop insulin resistance for two historical (and evolutionary useful) reasons.  First , in times of starvation, insulin resistance helps shunt any extra glucose to the large, energy demanding brain (12-1400 cc and consuming around 25% of our energy). This temporary peripheral insulin resistance helps turn on fat burning and when extra carbs are eaten, there is very little insulin response because glucose can be taken up in the brain without insulin.
The second reason to develop insulin resistance is to store fat in times of plenty of food. This system is mostly stimulated by high carbohydrate foods. The resulting chronic high insulin response shuts off fat burning, down regulates spontaneous energy expenditure, blocks leptin, and stores extra energy as fat. This metabolic syndrome probably works best as a temporary and seasonal effect.  I think we see this in animals preparing for hibernation who need to store fat as they subsequently rely on it as a fuel source for extended periods. The idea is that we can’t down regulate brain fuel demands, so need fat stores to help with this. We have much more fat mass and less lean muscle mass than a chimp who has a brain 1/3 the size of ours. So really the evidence is that we are designed to store and use fat. We easily put weight on to provide a source of constant fuel through fat for times of low food availability.
So insulin resistance is a really useful mechanism in human evolution and survival.  The problem now though is that insulin resistance is also caused by inflammatory processes and other means through the following things at least (there are probably more) – stress, poor sleep, too much exercise, too little exercise, high sugar diet, high Omega 6/trans fat diet, poor gut micro biome, high alcohol diet, age?, obesity, genes, smoking, pollution, other environmental toxins, too much sun, too little sun……
So I think you see the problem.  Modern life induces insulin resistance.  Some are more prone than others.
When you become insulin resistant then you will have trouble moving carbs (glucose) into your cells.  You probably will be able to do this, but just need loads of insulin to do so. So a relatively high amount of even “healthy carbs” for the insulin resistant person can result in constantly high insulin. We call this “hyperinsulinemia”.
This condition is probably the mechanism which causes most modern chronic diseases – cancer, diabetes, CVD, and neurological degeneration. Hyperinsulinemia is the direct and indirect cause of these. The mechanistic, epidemiological, and experimental evidence is strong.
Chronic hyperinsulinemia probably also makes you more insulin resistant and it becomes a vicious cycle.
Here’s why:
  • Humans who are not insulin resistant can thrive on higher carb diets as long as they don’t live a western industrial food and stress lifestyle.
  • Modern society is toxic in so many ways to our basic function – because it induces insulin resistance through inflammation.
  • Reducing dietary carbs for those who are insulin resistant (also know as metabolically dysregulated, also sometimes called carbohydrate (in)tolerance) is a useful way to proceed. Probably we can reset the system using this method, but we must first stop chronic hyperinsulinemia. More work needs to be done to understand exactly how this might work and if and when carbs might be eaten again in bigger quantities.
  • Living a life which resembles that of your ancestors minimises our chance of becoming metabolically dysregulated.
  • People vary in their personal carbohydrate tolerance and how that affects their health because they vary in their insulin resistance.
  • When you go on a low carb high fat diet you can burn fat, feel energised and easily manage your own hunger and eating.  Will power is over rated, especially in the face of dysfunctional physiology.
Anyway that’s a quick scientific primer from my perspective and the basic mechanisms behind what I am talking about. Here’s a reference for the adventurous and scientifically minded which goes in to more detail – Lifestyle and nutritional imbalances associated with Western diseases: causes and consequences of chronic systemic low-grade inflammation in an evolutionary context

7 Comments on “Why you are designed to eat and burn fat…your big brain

  1. from the Stuff article on the 27th October –

    “Heart Foundation nutrition adviser Delvina Gordon said the high amounts of saturated fats in Schofield’s plan were an issue.

    “That’s where we differ. We want to focus on healthy types of fats and oils,” Gordon said. “

    So close, yet so far.

  2. while many of the principles stated are understandable and you would think it would help those who are glucose intolerant (insulin resistant)to avoid to much glucose by eating low carb diets. I mean if your glucose intolerant then maybe you should not being eating alot of glucose, for me alas low carb diets didn’t work it did not make me feel better in the long run, it did not help with my hypoglycmic episodes it did not reduce insomina (but made it worse) it did not stifle cravings for carbs. it only increased my nervousness and increased my blood pressure over time. the first time i spent about 3 months on it was losing weight but my other symptoms did not subside. I tried to tweak it a bit in many ways but it didnt work. so now i just try to eat the highest quality carbs I can making sure to eat 100 percent whole grain stuff. and make sure to eat plenty of protein veggies or nuts and fruit i can with it. I have dealt with my obesity hypertension and metablic syndrome for nearly fourty years and tried every kind of program idea and supplement out there, nothing worked for me long term, I am just figuring I probably will never figure it out before I die might as well just eat like I normally did before, just pick higher quality more nutrtioous foods (carbs) I can. I am starting to feel better sleeping better have lost the desire to munch all the time like before, maybe it was taking iron, vitad3 and cinnamon.

  3. Insulin does not downregulate spontaneous energy expenditure and it does not block leptin. Insulin actually causes a leptin response. You are also skipping over Acylation Stimulating Protein which can store fat independently of insulin and causes fat storage in response to dietary fat.

    “When you become insulin resistant then you will have trouble moving carbs (glucose) into your cells.” Actually people who are insulin resistant from energy excess move more glucose into their cells than other people, primarily through mass action. The high blood sugar is because hepatic insulin resistance prevents insulin from turning off gluconeogenesis.

    • I think you need to consider the acute v chronic effects of insulin. Acutely in the metabolically well regulated humN it does what you say. Chronic hyperinsulinemia does the antagonistic

      How is glucose transport the same rate when there is impaired glucose homeostasis. Impaired rate is the actual definition.

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