Increased Diabetes Risk Due to Age at Onset of Obesity and Cumulative Exposure

Obesity is a well-known risk factor for type 2 diabetes, so much so that the 2 are considered ‘twin epidemics.’ More than 90% of people with type 2 diabetes are overweight or obese, and the recent rise in diabetes diagnoses is correlated with increasing obesity rates.¹

However, weight is a dynamic measure, and trajectories vary over time. Little is known about how onset time or cumulative exposure to obesity impact diabetes risk. Now, a recent study published in Diabetologia shows that diabetes risk is associated with younger age at onset of obesity, and longer exposure to obesity.²

Researchers used data from the Australian Longitudinal Study on Women’s Health, a population-based analysis of Australian women studying the effect of various factors on health. Over 19 years, they gathered data from 11,192 initially diabetes-free women aged 18-23 years, focusing on BMI and incidence of type 2 diabetes.

The researchers identified 6 BMI trajectories, which varied by baseline BMI and rate of increase. Women who were initially overweight or obese, or became so over the course of the study, had a significantly increased risk of developing diabetes.

However, the data also showed that cumulative exposure to obesity increased diabetes risk. The researchers measured exposure using obese-years, which account for both duration and magnitude of obesity. A higher number of obese-years, indicating more cumulative exposure, was positively associated with diabetes. Women with less than 10 obese years were 2.18 times more likely to develop diabetes, while women with 30 or more years were 5.88 times more likely.

Researchers also found a negative association between age at onset of obesity and diabetes risk. This may be because women with early-onset obesity are likely to have a longer duration of obesity, thus increasing cumulative exposure. Additionally, obesity at a young age may have more impact on insulin resistance.

Women with rapidly increasing BMIs were more at risk than women with stable trajectories. Normal weight subjects classified as rapid increasers were more likely to develop diabetes than their stable weight counterparts. Likewise, overweight and obese rapid increasers were more at risk than the baseline-only overweight and obese groups.

This study sheds new light on the importance of obesity timing and exposure in young women. Early-onset obesity should be considered an independent risk factor for type 2 diabetes. Over half of the cohort experienced a rapid BMI increase in young adulthood, highlighting this age group as a population that should be routinely counseled about weight management.

Health care providers should encourage these patients to monitor their weight and weight change over time to prevent early-onset and rapid-increase obesity. Not only preventing obesity, but even delaying age at onset and reducing exposure, may significantly decrease diabetes incidence.

M. May Zhang is a 2022 PharmD Candidate at the University of Connecticut in Storrs.

REFERENCES

• Type 2 Diabetes and Obesity: Twin Epidemics. American Society for Metabolic and Bariatric Surgery. https://asmbs.org/resources/weight-and-type-2-diabetes-after-bariatric-surgery-fact-sheet. Published December 30, 2014. Accessed January 8, 2020.
• Luo J, Hodge A, Hendryx M, Byles JE. Age of obesity onset, cumulative obesity exposure over early adulthood and risk of type 2 diabetes. Diabetologia. December 2019. doi:10.1007/s00125-019-05058-7.