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Recent Weight Gain May Not Mean Increased Risk of Type 2 Diabetes

But weight reduction still important in lowering risk….

It is known that people who are overweight or obese have a higher risk of developing diabetes. Because of this association, a common assumption is that people who experienced recent weight gain are more likely to be diagnosed with diabetes. In this prospective cohort study, researchers tested the hypothesis that substantial weight gain precedes a diagnosis of diabetes and explored more generally the patterns of body weight and composition in the years before people develop diabetes. They then examined whether changes in body weight corresponded with changes in other risk factors for diabetes (such as insulin resistance), lipid profiles and blood pressure.

Dorte Vistisen and Kristine Færch, from the Steno Diabetes Center in Gentofte, Denmark, and colleagues studied 6,705 participants from the Whitehall II study, an observational prospective cohort study of civil servants based in London. White men and women, initially free of diabetes, were followed with 5-yearly clinical examinations from 1991–2009 for a median of 14.1 years (interquartile range [IQR]: 8.7–16.2 years). Over the course of the follow-up, 645 subjects developed diabetes; the diagnosis was identified by healthcare providers. Of the 645 diabetic subjects, 606 were considered "stably overweight"; their BMI changed very little from the start of the study. Five years prior to the diagnosis, the 606 stably overweight subjects had minor decline of beta cell function and insulin sensitivity. A total of 15 subjects who developed diabetes progressively gained weight in the years leading up to their diagnoses which lead to a linear rise in blood pressure and insulin resistance, and 26 subjects, who were labeled as persistently obese, had relatively stable insulin sensitivity.

These results suggest that diabetes development is a complicated process, and one that differs between individuals who end up with the disease. They call into question the common notion that most people who develop diabetes have recently gained a lot of weight or are obese. A substantial rise in insulin resistance, another established risk factor for diabetes, was only seen in the smallest of the groups, namely the people who gained weight consistently for years before they were diagnosed. When the scientists applied the Framingham diabetes risk score to their largest "stably overweight" group, they found that these people were not classified as having a particularly high risk, and that their risk scores actually declined in the last five years before their diabetes diagnosis. This suggests that predicting diabetes in this group might be difficult.

The researchers applied their methodology only to this one cohort of white civil servants in England. Before drawing more firm conclusions on the process of diabetes development, it will be important to test whether similar results are seen in other cohorts and among more diverse individuals. If the three groups identified here are found in other cohorts, another question is whether they are as unequal in size as in this example. And if they are, can the large group of stably overweight people be further subdivided in ways that suggest specific mechanisms of disease development? Even without knowing how generalizable the provocative findings of this study are, they should stimulate debate on how to identify people at risk for diabetes and how to prevent the disease or delay its onset.

Patterns of Obesity Development before the Diagnosis of Type 2 Diabetes: The Whitehall II Cohort Study, PLoS Medicine February 11, 2014