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Decreasing BMI from young adulthood to midlife reduces incident diabetes risk

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March 6, 2018

Adults with obesity in young adulthood who dropped to a nonobese BMI category during midlife had reduced risk for developing diabetes compared with adults with stable obesity during that life stage, study data show.

Andrew Stokes, PhD, assistant professor in the department of global health at the Center for Global Health and Development at Boston University, and colleagues evaluated data from the National Health and Nutrition Examination Survey (1988-1994; 1999-2014) on 21,554 adults to determine the association between self-reported weight change from young adulthood to midlife and incident diabetes. Participants reported weight change from recall of weight at age 25 years and at 10 years before NHANES. The mean age of the participants was 43.8 years at baseline, 50.2% were men, 78.9% were white, mean BMI was 23.6 kg/m2 at age 25 years, 26.6 kg/m2 at 10 years before the survey and 27.8 kg/m2 at the end of follow-up.

“This study used a novel application of NHANES survey data to explore the associations and implications of weight change from young adulthood through midlife and demonstrated the variability of using historic self-reported weight data for longitudinal analyses,” the researchers wrote. “We showed that remaining or becoming obese raises the risk of incident diabetes relative to remaining nonobese. The findings from a national sample underscore the importance of developing policies and programs that reduce the prevalence of obesity.”

Participants were divided into group BMI change categories based on BMI at age 25 years and at 10 years before the survey: stable nonobese (n = 16,454; BMI < 30 kg/m2 at age 25 years and 10 years before the survey), losing (n = 227; BMI 30 kg/m2 at age 25 years and BMI < 30 kg/m2 10 years before the survey), gaining (n = 3,719; BMI < 30 kg/m2 at age 25 years and BMI 30 kg/m2 10 years before the survey) and stable obese (n = 1,154; BMI 30 kg/m2 at age 25 years and 10 years before the survey).

Cox proportional hazard models were used to test two hypotheses, the “risk reduction” hypothesis and “residual risk” hypothesis, to predict the rate of incident diabetes across the four categories. The stable-obese weight-change category was used at the reference category to test the risk hypothesis, and the stable-nonobese category was the reference category to test the residual risk hypothesis. The residual risk hypothesis predicted that participants who had ever had obesity were more likely to develop diabetes compared with those who never had obesity.

Compared with the stable-obese group, the stable-nonobese group had a lower risk for developing diabetes during the 10 years of follow-up (HR = 0.22; 95% CI, 0.18-0.28). Further, compared with the stable-obese group, those who lost weight had 0.33 times the risk for developing diabetes and those who gained weight had 0.7 times the risk for developing diabetes.

The risk for developing diabetes did not differ between the stable-nonobese group and those who lost weight or maintained stable obesity.

An estimated 9.1% of diabetes cases could have been avoided among participants with obesity if they lost weight to a nonobese BMI category, and 23.5% of cases could have been avoided if participants who gained weight did not gain weight.

“In testing the risk reduction hypothesis, we found those who lost weight between young adulthood and midlife showed statistically significant reductions in risk for diabetes onset compared with those who remained obese,” the researchers wrote. “When considering the residual risk hypothesis, those who had been obese at age 25 but had subsequently become nonobese had a higher risk of developing diabetes than those who remained nonobese throughout their life course, but the difference was not statistically significant. A large percentage of the observed diabetes cases could have been averted with effective intervention and prevention efforts in young adulthood.” – by Amber Cox

Disclosures: Stokes reports he received research funding from Johnson & Johnson. Please see the study for all other authors’ relevant financial disclosures.