Waist Size not BMI Best Indicator for Type 2 Diabetes

Overweight people with a large waist are just as likely to develop type 2 diabetes later in life as those who are obese, according to results from the largest international study of its kind to date.
The study, led by the Medical Research Council (MRC) Epidemiology Unit, followed more than 340,000 people from eight European countries to examine their future risk of type 2 diabetes. 
The results, published in PLoS Medicine, show that waist circumference is strongly associated with type 2 diabetes, even after accounting for body mass index (BMI). This association was particularly pronounced in women. 
Overweight men and women (BMI 25 to 29.9 kg/m2) with a large waist (over 102cm for men and over 88cm for women) were found to have a similar risk of developing diabetes as those who are clinically obese (BMI over 30). 
Dr Claudia Langenberg from the MRC Epidemiology Unit in Cambridge, who led the study, said:
“Type 2 diabetes is a serious and increasingly common disease. More than a third of the UK adult population is overweight and at increased risk of diabetes, but they are not systematically monitored for this risk. Our findings suggest that if their waist circumference is large, they are just as likely to develop the condition as if they were obese. 
“We do not suggest replacing BMI as a core health indicator, but our results show that measuring waist size in overweight patients allows doctors to ‘zoom in’ on this large population group and identify those at highest risk of diabetes. These people can then be offered lifestyle advice, which can reduce their risk of developing the disease.”
Type 2 diabetes is a chronic condition that occurs when the body fails to produce enough of the hormone insulin, which controls blood sugar levels, or when the body’s cells do not react properly to insulin. While the exact causes of type 2 diabetes are not fully understood, being overweight or obese are the most important modifiable risk factors.
To investigate the association between BMI, waist circumference* and type 2 diabetes risk separately in men and women, the researchers looked at data from the EU-funded InterAct Study, in which 12,403 cases of type 2 diabetes developed over the 15 years of follow up.
The researchers found that 7 per cent of men and 4.4 per cent of women who were overweight and had a large waist went on to develop diabetes within 10 years. This risk was equivalent to, or in some cases higher than, obese participants. 
In contrast, risk was much lower in normal weight participants who had a small waist, with only 1.2 per cent of men and 0.6 per cent of women in this group developing diabetes over the same time period. Those who were overweight but had a small waist – the so-called ‘pear-shapes’ – were also at relatively low risk from the disease.
Obese women (BMI greater than 35 kg/m2) with a large waist were almost 32-times more likely to develop type 2 diabetes than lean women (BMI 18.5–22.4 kg/m2) with a small waist, while men in the equivalent group were 22-times more likely to get the condition than those with a low BMI and small waist.
Half the men and a third of the women in the cohort were overweight, and another 16.4 per cent of men and 15.8 per cent of women were obese, highlighting the epidemic of overweight and obesity and future burden of diabetes in Europe.
Professor Nick Wareham, Director of the MRC Epidemiology Unit and Principal Investigator of the InterAct Study, said: 
“This is one of the most comprehensive studies of lifestyle and diabetes risk to date, not just in scale, but in the powerful prospective design which allows us to follow a population over a long period of time to see how and why disease develops. The results of this important research will help inform new strategies for the prevention of this devastating condition that affects almost three million people in the UK.” 
The study was a collaboration across 26 European Prospective Investigation into Cancer and Nutrition (EPIC) centres including the University of Oxford and Imperial College London in the UK. It was funded by the European Union.

*Waist circumference was measured either at the narrowest circumference of the torso, or at the midpoint between the lower ribs and the top of the hip bone (iliac crest).

Article published: 6 June 2012

Article from: http://www.mrc.ac.uk/Newspublications/News/MRC008701