Having a ‘healthy’ BMI is not necessarily as healthy as we think

The body mass index (weight in kg divided by the square of someone’s height in metres) is well-established as a marker for health. Generally speaking, we’re told that BMIs of 18.5 are ‘normal’ and ‘healthy’, while those of 25.0-29.9 are ‘overweight’, and those 30 and above mark people out as ‘obese’ There’s a number of problems with the BMI, though, not least of all that that they tell us nothing about the composition of the body. So, it’s possible to bit fit, healthy and well-muscled, and have a BMI that classifies you as overweight and even obese Also, you can be frail, have low muscle mass, and be classified as healthy. Using the BMI to judge health is therefore, largely, a nonsense.

Another issue with the body mass index is that it tells us nothing about the distribution of weight (specifically, fat) in the body. This is important because there has been growing recognition of the fact that weight around the middle (particularly weight packed in and around the inside of the abdomen) has strong links with diseases such as heart disease and type 2 diabetes. On the other hand, weight under the skin, say on the legs or arms, does not seem to be a particular risk factor for ill-health.

The fact that abdominal fat has been identified as a marker for ill-health has led to increasing popularity of measures of abdominal fat such as the ‘waist circumference’ and the ‘waist-to-hip ratio’.  This is all good, I think, but as a recent paper points out, such measurements are only generally used in individuals who are branded ‘overweight’ or ‘obese’ on the basis of their BMI [1].

The authors of this study set about seeing what value the waist circumference was in predicting risk of developing diabetes in those of ‘normal’ BMI. And they also compared the apparent risk to those considered ‘overweight’ and ‘obese’, but whose waist circumference was not particularly expanded. The researchers followed more than 25,000 men and women aged 35-65 over and average of 8 years.

In men, median waist circumference was 94 cm (37 inches). In women, it was 78.5 cm (31 inches). In both men and women, lowest risk for diabetes was seen in those with waist circumferences below the median who also had a BMI value of less than 25 (‘healthy’).

In men, compared to the low risk group, those with lower waist circumference but ‘overweight’ BMIs were, on average, 2.26 times more likely to develop type 2 diabetes.

Those with higher waist circumferences and ‘overweight’ BMIs were almost 5 times more likely to develop type 2 diabetes.

But what about those with ‘healthy’ BMIs and higher waist circumferences? These individuals were, on average, 3.62 times more likely to develop diabetes.

And it was a similar story in women: Women with lower waist circumferences and ‘overweight’ BMIs were not found to be at a statistically significant increased risk of diabetes.

However, those with higher waist circumferences and ‘healthy’ BMIs were 2.74 times more likely to develop diabetes than those with ‘healthy’ BMIs and lower waist circumferences.

Here are a couple of quotes from the authors of this study:

“The relative risk (RR) of developing type 2 DM [diabetes mellitus] among persons of low or normal weight (BMI <25) who had a large waist circumference was at least as high as that among overweight persons (BMI 25.0-29.9) with a small waist circumference.”

and

“These findings imply that the waist circumference is an important additional piece of information for assessing the risk of type 2 DM, particularly among persons of low or normal weight.”

To my mind, this study highlights the importance of focusing on keeping the body free of excess fat around the middle (not weight or BMI). It’s one of the reasons I wrote my latest book Waist Disposal.

References:

1. Feller S, et al. Body mass index, waist circumference, and risk of type 2 diabetes mellitus. Dtsch Arztebl Int 2010;107(26):470-6

Diabetes costs ‘out of control’, and why this is no surprise given standard dietary advice for diabetics

I saw this story on the BBC website this morning. It concerns the costs of treating those with diabetes. Apparently, the cost of drugs for managing diabetes is rising (a lot), and now accounts for 7 per cent of the total amount spent on prescribing in the UK. Between 2000 and 2008 prescriptions for diabetic drugs rose by 50 per cent, apparently, and costs (even taking into account inflation more than doubled.

What to do? Well, for a start, perhaps people could be given appropriate advice regarding how to eat to better control their diabetes. Sugary and starchy carbohydrate tends to cause considerable disruption in blood sugar levels. So, it makes sense that limiting such foods may well improve blood sugar (‘glycaemic’) control. Not so long ago I reported on a study which employed a low-carb diet in a group of type 2 diabetes. The result: more than 95 per cent of them were able to reduce or stop their medication.

Admittedly, the diet used in this study was really quite low in carb. But it gives some indication of the sort of results that can be achieved by employing the logical and correct nutritional approach to diabetes.

I was interested to read the comments of Dr Niti Pall – a spokesperson for Diabetes UK (the UK’s pre-eminent diabetes charity) – in the BBC news story linked to above. She claims, according to the article, that the job of GPs is to get blood sugar levels as low as possible by whatever means possible. Really? Because, such an approach may promote attacks hypoglycaemia (low blood sugar) that can cause symptoms such as weakness and confusion. Sometimes, hypoglycaemia can cause injury and even death.

Maybe Dr Pall is aware of this but neglected to mention it in her enthusiasm regarding getting blood sugar levels as low as possible. But even if we ignore the obvious gaff regarding hypoglycaemia, is it really true that getting blood sugar levels as low as possible is the best way forward? I ask this because there is some evidence that intensive lowering of blood sugar levels using pharmacological agents (i.e. insulin and/or other diabetes drugs) actually increases risk of death [1].

Should we be too surprised that perhaps not the best advice for diabetics has come out of Diabetes UK? Maybe not, bearing in mind that it is this organisation which continues to advise diabetics to eat like this (taken from the Diabetes UK website):

At each meal include starchy carbohydrate foods
Examples of these include bread, pasta, chapatis, potatoes, yam, noodles, rice and cereals. The amount of carbohydrate you eat is important to control your blood glucose levels. Especially try to include those that are more slowly absorbed (have a lower glycaemic index) as these won’t affect your blood glucose levels as much.

However, even the lower GI foods recommended here can be very disruptive for blood sugar levels, especially when eaten in quantity (as they often are). This advice, if acted on, will generally destabilise blood sugar levels in a way that will do little or nothing to help individuals control their condition and reduce their medication or even eliminate the need for medication entirely. But, then again, as I commented here, perhaps that’s the point.

References:

1. Action to Control Cardiovascular Risk in Diabetes Study Group. Effects of intensive glucose lowering in type 2 diabetes. N Engl J Med 2008;358(24):2545-59