medwireNews: The length of time that a young woman has been obese together with its magnitude can collectively impact on the risk for developing type 2 diabetes, an Australian study has revealed.
The findings in 11,192 Australian women aged 18 to 23 years at baseline who were monitored for up to 19 years showed that their likelihood of developing type 2 diabetes increased the longer they had been obese and the greater their “obese–years” – calculated by multiplying BMI units above 30 kg/m2 by the years at that BMI.
“The results highlight the importance of preventing or delaying the onset of obesity and reducing cumulative exposure to obesity to substantially lower the risk of developing diabetes,” say the researchers.
“We recommend that people self-monitor weight change over time, and that healthcare providers attend to weight change in addition to static weight as another risk factor for diabetes.”
The women were free of diabetes when they entered the Australian Longitudinal Study on Women’s Health in 1996, after which they were surveyed approximately every 3 years during which self-reported weight was collected up to a total of seven times.
During a mean of 16 years of follow-up, 162 (1.5%) women were newly diagnosed with type 2 diabetes and obesity prevalence increased from 6.5% at baseline to 25.7% at the seventh survey, with a mean of 8.4 obese–years among the 2008 women who became obese.
Among the 10,521 women who were not obese at the start of the study, those who became obese were 3.01-fold more likely to develop type 2 diabetes compared with the others.
And each extra year delay in the onset of obesity was associated with a 13% decreased likelihood for developing type 2 diabetes among those who became obese.
Furthermore, the odds of developing diabetes increased significantly with the number of obese–years.
Compared with women who did not become obese during follow-up, those with less than 10 obese–years had a 2.18-fold increased likelihood of developing type 2 diabetes, while for women with between 10 and 30 obese–years this rose to 3.01-fold and for those with 30 or more obese–years it rose again to 5.88-fold.
Women who were obese at baseline had a 7.07-fold increased likelihood of developing type 2 diabetes, when BMI only at this timepoint was examined.
But for those who were obese and put on weight rapidly during the study, the likelihood of developing type 2 diabetes was 10.06-fold that of normal-weight women at the low end of the category who remained at stable weight.
Reporting in Diabetologia, Juhua Luo (Indiana University, Bloomington, USA) and colleagues write: “[O]ur data have shown that more than half of the women experienced a rapid BMI increase from early to middle adulthood, suggesting the importance of monitoring weight change over time.”
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