Why some people stay skinny and others get fat

Obesity

What I want to put forward today is that there is evidence for two distinct modes of human metabolic state. One is being “fat adapted”. That is, a state where the hormone insulin is well controlled and the body is able to access its stores of fat as a primary source of fuel. This, I contend, is the normal human state. The complex interaction of cells, hormones, enzymes and much much more is in balance.  We homeostatically maintain a desirable body weight by self-regulating inputs and outputs. In this state, if we over-eat, we will compensate and burn it off.  And vice versa if we under-eat. The mechanisms are complex and not all are well understood.  It’s at least a great starting hypothesis.  Good science is  needed to nail down the whole mechanism but putting together animal and human evidence points to this.  This is fundamentally why the “calorie is a calorie” dogma that has plagued nutritional science for the past 40 years is wrong.

When you are “fat adapted” you can easily utilise fat, you have less craving for simple carbs and, most importantly, insulin is well controlled.

However, when you continually eat large amounts of carbohydrates, especially simple refined carbs, then the second mode of human metabolic state results and the body becomes what I have decided to term “metabolically dysregulated”. Others have used the term “metabolically deranged”, but I find that a little too emotional!  The mechanism is simplified as follows:

  1. The body has to continually deal with large loads of dietary carbs.
  2. It does this by producing insulin, a storage hormone which shuts off the ability to burn fat as a fuel source and get carbs into cells. Some will go into muscle cells (especially in an active individual); some goes into the liver; but if the muscle cells and liver are full, which they often are because they have a limited capacity and people often expend very little energy, then the carbs are stored in fat cells.  That’s the basic mechanism for the storing of fat.  Insulin also drives extra fat into fat cells too. That’s it. Simple.  Insulin makes fats cells get bigger. Without a rise in insulin, there is no easy mechanism for this process.
  3. Insulin also blocks an important hunger hormone called leptin. Leptin is secreted by fat cells and signals to the hypothalamus in the brain that the body is not starving. By blocking this hormone, insulin is effectively block the “off switch” for hunger so we over-eat.
  4. Insulin also down-regulates (the process by which a cell decreases the quantity of a cellular component) the pleasure hormone dopamine’s receptors in the brine. This is what gives simple carbs their addictive quality.
  5. Insulin also down-regulates sympathetic nervous system activity resulting in a reduced propensity to expend energy through both incidental and purposeful physical activity.
  6. It’s a downward spiral as you get fatter and less regulated and continue to bombard the body with large doses of dietary carbs. You become more and more insulin resistant, both at the muscle and liver cell level.  In other words, you need more and more insulin to get the carbs into the cells. Insulin is permanently high.  So your cells become more existent.  You are always storing fat, never burning it and a state of hyperinsulemia (high insulin) ensues, even when you are not eating. You become fatter, especially around your central area (visceral obesity), which drives more inflammation and increased insulin resistance.  Oh boy….!
  7. Eventually, the beta cells in the pancreas which produce insulin start to fail and you can’t manage your blood sugar levels at all. That’s Diabetes. Constantly high blood sugar is toxic to all parts of the body it touches, and it touches everything of course.

So that is what I call becoming metabolically dysregulated.  It is caused by lots of simple dietary carbs. It’s a pandemic.  It’s because we have a food supply choked full of processed carbs. And even worse, our medical advice is to go low fat. Low fat, by definition, will mean high carb for the body.  More on why in later blogs.

So that’s the dietary choice you have in my view. Eat whole unprocessed foods; low carb, leafy vegetables, moderate protein, high fat and you will avoid the insulin peaks and eventual dysregulation described above.  Eat the carbs, send insulin way up and suffer the consequences of metabolic dysregulation. Fat burning shuts down,energy out shuts down.  Fat storage goes up.  Because energy out is synonymous with quality of life, you feel crap. Being the best you can be has a central requirement of being metabolically well regulated.  That’s why I am so interested in nutrition.

Thanks to Helen Kilding for her help with this blog

Author: Prof. Grant Schofield

I am Grant Schofield, Professor of Public Health at Auckland University of Technology and director of the university's Human Potential Centre (HPC) located at the Millennium Campus in Auckland, New Zealand. My research and teaching interests are in wellbeing and chronic disease prevention especially reducing the risk and eventual mortality and morbidity from obesity, cardiovascular disease, and diabetes. I live by the motto "be the best you can be" and have a strong commitment to peak performance in which I also do consulting work. I’ve been interested in human health and performance for my whole career. I started in psychology, went into sport and exercise psychology, then into public health, especially physical activity, then obesity. There have been some twists and turns along the way, which are the reasons for why I do what I do – you can read about those in my first blog entry. I want to know how we can be the best we can be. This crosses disciplines such as biology, medicine, pubic health, and productivity management. The cornerstones are nutrition, exercise, sleep, neuroscience, psychology and wellbeing. In my blog, I cover these topics under the broad heading of the Science of Human Potential.

16 thoughts on “Why some people stay skinny and others get fat”

  1. Aw, this was an extremely nice post. Spending some time and actual effort to produce a
    great article… but what can I say… I put things off
    a lot and never manage to get anything done.

  2. Hello there! This is kind of off topic but I need some help from an
    established blog. Is it hard to set up your own blog? I’m not very techincal but I can figure things out pretty quick. I’m thinking
    about creating my own but I’m not sure where to start. Do you have any ideas or suggestions? Thanks

  3. “Insulin also down-regulates … the pleasure hormone dopamine’s receptors in the brine.”

    Is that the ‘sauce’ of the conventional recommendation to reduce salt intake? ;))

    Great to see another good blog, adding to those in Iceland, Sweden, UK, France, USA & others.

  4. Very interesting post! My tutor was recently telling us about this theory. The dogma of fat being the culprit is so ingrained into society though- everything directed at losing weight is low fat low fat low fat. At the moment, I feel that most people approach the “fat is ok sugar is bad” message with a lot of skepticism. Posts like this should be more widely spread, thanks for sharing.

    Although the title of the post made me think it was going to be about metabolic setpoint. One of my lecturers told us that our metabolic setpoint is pretty much genetic and virtually unchangeable. What is your take on that?

  5. Hi! I’m right behind you on this and loved your recent article, so you’re preaching to the converted here, but to my mind this article doesn’t really answer the question you pose in the heading. I know people who eat high carb (but otherwise fairly healthy) and are slim (and don’t need to diet or exercise excessively). My own thoughts are that we have different carb/fat tolerances and that a high carb diet might well be best for them. This is along the lines of William Wolcott’s Metabolic Diet (book available in Auckland library). I agree that there is probably some genetic element. Set point or carb tolerance?

    1. Oh yes, I think you are dead right – the reality is that we vary in insulin resistance – that could also be called carb tolerance.
      And – all the events of everyday modern life affect insulin resistance too – sugar, stress, pollution etc etc. So insulin underpins it all – how we deal woth carbs. So some are very sensitive and move the glucose away quickly and insulin returns to baseline. Others do not,

  6. I’ve gone one step further in my search for answers as to why I am unable to shift down past 118 k. I have Hashimotos, sleep aponea (Use a CPAP) machine and yes high stress levels although this is improving.

    Recently I had DNA genetic profiling done with 23 and me and have been working with a bio pharmacist to see what else I can discover. My body is not processing B12 well MTHFR probs, I have CBS mutation and have too much sulphur and ammonia in my system among other things and basically a toxic overload. I have also been advised to have a bone density test after the review of my results.

    It’s been recommended that I go low sulphur in my food and cut back on protein, my food choices diminish yet again. Over the last few years I have lost 10 k and kept it off by going grain and gluten free – free as gluten free products are not that good for blood sugar levels. My blood sugars are fine and my blood pressure is ok. I don’t feel hungry or crave foods and have a poor sense of smell, so not much enjoyment in food.

    There are so many varients in epigentics that ultimately it comes down to what suits you and your body when it comes to a healthy eating lifestyle. Am I genetically inclined to stay this way until I can move the toxins?

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