Effect of past and concurrent body mass index on prevalence of glucose intolerance and Type 2 (non-insulin-dependent) diabetes and on insulin response

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Abstract
A representative sample (n=2140) of the Israeli Jewish population aged 40–70 (excluding known diabetic patients), whose body mass index had been measured 10 years earlier, underwent an oral glucose tolerance test and redetermination of body mass index. Irrespective of weight changes, high concurrent and high past body mass index values (≥ 27) were associated with similarly increased rates of glucose intolerance as compared with body mass index values < 27 at both time-points (rate ratio 1.76, 90% confidence limits 1.56–1.99). Glucose intolerance here includes borderline and impaired tolerance as well as Type 2 diabetes. The rate of Type 2 diabetes increased only with increasing past body mass index, while concurrent body mass index had no effect [rate ratios: 2.36 (1.48–3.75) and 1.99 (1.48–2.68) respectively for the medium-(23–26.9) versus-low (p < 0.001) in all concurrent body mass index categories from normal tolerance through borderline to impaired tolerance, and decreased significantly (p < 0.001) in diabetes relative to impaired tolerance, although it remained above normal. Means of sum insulin within each glucose tolerance level were similar in the two lower concurrent body mass index categories, with markedly higher (p < 0.001) levels in the high body mass index category. All these findings held after accounting for age, sex, ethnic group and use of antihypertensive medications. We conclude that body mass index ≥ 27 leads to early impairment in glucose tolerance. A prolonged period of obesity is apparently required for the development of Type 2 diabetes and its associated reduced insulin response. The reversibility of the deterioration of glucose tolerance seems to be limited.