Diabetes prevention should focus on prediabetes not obesity

Fight the Obesity Epidemic. Fine sounding words upon which careers have been built. Everyone knows, because the experts say so, that obesity is the main driver of the increase in type 2 diabetes. Everyone is wrong.

 

In the UK, 62% of adults are overweight or obese, and of that sixty-two percent 12.4% have type 2 diabetes. In comparison 2.5% of normal or low weight adults in the UK have diabetes. A bit of high school maths and we have the much quoted figure that 90% of type 2 diabetics are overweight or obese. Take a sample of one thousand adults, 620 are overweight or obese and 77 of these have type two diabetes. 320 are normal or low weight. Eight of these have type two diabetes. 77/85 comes to 90%.

 

However, obesity is not the main driver of the predicted increase in the number of cases of type 2 diabetes over the next generation or two. Population ageing and population browning are both predicted to be more important than an increase in the average weight of the adult population. Ageing is obvious, and people of colour happen to be more susceptible to type 2 diabetes than are whites.

 

The truth is that most overweight or obese people will never develop type 2 diabetes. Never. If you are overweight or obese, your lifetime risk of developing diabetes is perhaps as high as 30%. It is no higher. This is an easy enough figure to substantiate, although there is no rush among the public health authorities to collect the appropriate data – what proportion of overweight or obese people have type 2 diabetes when they die? That’s the lifetime risk.

 

Or, to put this another way, if we were to follow a randomly selected population of non-diabetic overweight and obese people, about one percent of them would develop type 2 diabetes each year.

 

So why do we spend millions of tax dollars each year demonising the eating habits of overweight and obese folk? The main outcome is a lot of anxiety, a lot of guilt, and a lot of inconvenience among a lot of people who have nothing to worry about. Once again, there is no rush among the public health authorities to calculate how many thousands, tens of thousands, or even millions of dollars are spent to prevent one person developing diabetes as a result of following the public health messages.

 

One answer, and it would be a good answer if it were true, is that there is no telling which overweight and obese people will develop type 2 diabetes. That it’s just bad luck. However, this just isn’t true.

 

The presence of prediabetes is a sensitive and specific way to predict who will develop type 2 diabetes. About 11% of people, fat or thin, with prediabetes will develop type 2 diabetes each year if nothing is done. No-one without prediabetes will develop diabetes in the next year. The blood test for prediabetes is the same as that for diabetes, the (haemoglobin) A1c level. If this is 50 or more, and still exceeds this level on retesting if there are no symptoms of diabetes, then a diagnosis of diabetes is confirmed. If this is in the range 41-49 then that is prediabetes. People with prediabetes are on the way to diabetes.

 

The good news is that it is a lot easier to reverse prediabetes than it is to drop enough weight to move from obese to normal. A cheap safe drug called metformin might well do it. Losing four kilos could be enough. A week fasting or on a very low calorie diet may do the trick. And exercise. Don’t forget exercise.

 

For people who find they are not prediabetic but are still worried about whether prediabetes is on the horizon, another blood test, fasting insulin, identifies a precursor problem called insulin resistance.

 

The solution to the ‘diabetes epidemic’ has nothing to do with spending millions of dollars telling people who enjoy eating that they are doing it wrong. The number of new cases of type two diabetes will fall if the pool of people with prediabetes is reduced in number. The number of new cases of type two diabetes will not fall if the pool of overweight or obese people is reduced in number. This is simple stuff.

 

Reducing the size of the prediabetes pool is a two step process. First, we should use incentives to identify people with prediabetes. Encourage people to have the blood test each year. Make it something folk can walk into a community laboratory and have done for free, without a form from their doctor. Second, we should provide people with information on what works to reverse prediabetes or to reverse insulin resistance, and let them make the choice that suits them. Show, don’t tell.

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