What Causes Insulin Resistance? Part VII

In previous posts, I outlined the factors I'm aware of that can contribute to insulin resistance.  In this post, first I'll list the factors, then I'll provide my opinion of effective strategies for preventing and potentially reversing insulin resistance.

The factors

These are the factors I'm aware of that can contribute to insulin resistance, listed in approximate order of importance.  I could be quite wrong about the order-- this is just my best guess. Many of these factors are intertwined with one another. 
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What Causes Insulin Resistance? Part VI

In this post, I'll explore a few miscellaneous factors that can contribute to insulin resistance: smoking, glucocorticoids/stress, cooking temperature, age, genetics and low birth weight.

Smoking

Smoking tobacco acutely and chronically reduces insulin sensitivity (1, 2, 3), possibly via:

1. Increased inflammation
2. Increased circulating free fatty acids (4)

Paradoxically, since smoking also protects against fat gain, in the very long term it may not produce as much insulin resistance as one would otherwise expect.  Diabetes risk is greatly elevated in the three years following smoking cessation (5), and this is likely due to the fat gain that occurs.  This is not a good excuse to keep smoking, because smoking tobacco is one of the most unhealthy things you can possibly do.  But it is a good reason to tighten up your diet and lifestyle after quitting.

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A Roadmap to Obesity

In this post, I'll explain my current understanding of the factors that promote obesity in humans.  

Heritability

To a large degree, obesity is a heritable condition.  Various studies indicate that roughly two-thirds of the differences in body fatness between individuals is explained by heredity*, although estimates vary greatly (1).  However, we also know that obesity is not genetically determined, because in the US, the obesity rate has more than doubled in the last 30 years, consistent with what has happened to many other cultures (2).  How do we reconcile these two facts?  By understanding that genetic variability determines the degree of susceptibility to obesity-promoting factors.  In other words, in a natural environment with a natural diet, nearly everyone would be relatively lean, but when obesity-promoting factors are introduced, genetic makeup determines how resistant each person will be to fat gain.  As with the diseases of civilization, obesity is caused by a mismatch between our genetic heritage and our current environment.  This idea received experimental support from an interesting recent study (3).

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