Insulin Resistance in the Brain and What It Means for Dieters

Most people have been taught that increasing weight is the cause of insulin resistance, which in turn may cause an array of different health problems. That is only half true: insulin resistance may contribute to the development of obesity, and once we start gaining abdominal fat then that may indeed contribute to insulin resistance. So a vicious circle is established in which insulin resistance helps cause obesity, which in turn causes more insulin resistance.

Another thing that we have been taught for half a century that the brain is an insulin-insensitive tissue. What that means is that the uptake and use of glucose by the brain is not affected by circulating levels of glucose and insulin. That has always seemed a bit strange, because insulin is very important in cognition. Some experts believe that disturbances of insulin and closely related hormone – insulin like growth factor 1 (IGF-1) are involved in the pathogenesis of Alzheimer’s disease.

When someone is insulin resistant, they have high circulating levels of insulin, and an obvious question is whether these high insulin levels may interfere with the normal functions of the brain. This is not a new idea. It has been known for many years that high levels of triglycerides, that may be a marker for insulin resistance, may be associated with cognitive impairment in people with type 2 diabetes.

Now colleagues in London have found that people who have peripheral insulin resistance also have brain insulin resistance especially in two brain regions – the ventral striatum and prefrontal cortex – that are involved in appetite and reward.

It looks as if one of the reasons why people with insulin resistance become obese is that the normal link between the control of food intake and energy balance is broken.

This is yet more evidence that a simple diet will not work in the long term. If the problem is metabolic and involves damage to the mechanisms that control eating, the only way to help is to use a combined approach that deals not only with the composition of the diet, but the precise time when people should eat, and the psychological and social barriers that are left over from millions of years of evolution. I outline a comprehensive and highly successful weight management technique in Healing, Meaning and Purpose. Over the last few months I have had an enormous number of requests to expand that material into another book, and in between writing this blog, I am hard at work on completing a full account of exactly what we do to help people manage their weight.