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  1. Sarah H Wild, senior lecturer in epidemiology and public health1,
  2. Christopher D Byrne, professor of endocrinology and metabolism2
  1. 1University of Edinburgh
  2. 2University of Southampton

Diabetes

Body mass index at follow-up and relative risk for type 2 diabetes in participants in nurses' health study. Data derived from Colditz et al (see Further Reading box)

Many cross sectional and prospective studies have confirmed the association between obesity and type 2 diabetes. Most people with type 2 diabetes are overweight or obese: more than 85% of people with type 2 diabetes in southeast Scotland in 2005 had a body mass index (weight in kilograms divided by height in metres squared) of over 25. Recent evidence indicates that high waist circumference may be an even better indicator than body mass index (BMI) of increased risk of type 2 diabetes.

The risk of developing diabetes over a 14 year follow-up period (among nurses aged 30-55 years at baseline) in the nurses' health study was 49 times higher among women whose baseline BMI was >35 than among women whose baseline BMI was <22. Even a a slightly raised BMI (22.0-22.9) at follow-up was associated with an age adjusted relative risk of diabetes that was three times higher than that in women with a BMI of <22.0 at follow-up.

Distribution of body mass index in people with diagnosis of type 2 diabetes in past two years, by age at diagnosis (based on 371, 1466, 1302 people aged 25-44, 45-64, and ≥65 respectively at diagnosis, in population based diabetes register in Lothian, Scotland)

Similar findings have been reported for men from a United States cohort of 51 529 male health professionals aged 40-75 in 1986 who were followed until 1992. Those with a BMI of ≥35 had a relative risk of developing diabetes of 42 (95% confidence interval 22.0-80.6) compared with men with a BMI of <23.0 at age 21, after adjustment for age, smoking, and family history of diabetes. Moreover, earlier onset …

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