Reducing cumulative exposure to obesity may substantially lower risk of diabetes

Australia: Cumulative exposure to obesity and earlier development of obesity may increase the risk of diabetes development, a recent study in the EASD journal Diabetologia has found.

The findings indicate that reducing the cumulative exposure to obesity and the onset of diabetes may substantially lower the risk of developing diabetes.

It is a known fact that obesity is a risk factor for type 2 diabetes (T2D). Still, little is known about the relationship between the age of onset of obesity and cumulative exposure to obesity and the risk of T2D, especially among young adults.

Juhua Luo, School of Public Health, Indiana University, Bloomington, IN, USA, and colleagues conducted the study to to examine the associations between BMI trajectories, age of onset of obesity and obese-years (a product of degree and duration of obesity) over early adulthood and subsequent risk of type 2 diabetes.

The study involved women aged 18-23 years (n=11,192) enrolled in the Australian Longitudinal Study on Women's Health (ALSWH) in 1996. They were followed up about every three years via surveys for up to 19 years. Self-reported weights were collected up to seven times. New cases of T2D were self-reported. A total of 162 (1.5%) women newly developed T2D over an average of 16 years of follow-up. Six distinct BMI trajectories were identified, varying by different initial BMI and different rates of increase of obesity.

Key findings of the study include:

• Higher initial BMI was associated with an increased risk of diabetes.


• Increased age at onset of obesity was associated with a lower risk of diabetes, with a 13% lower risk of developing T2D per one-year delay in onset. A higher number of obese-years was associated with an increased risk of developing T2D. Obese years are calculated by a person's BMI minus the BMI for obesity (30), then multiplying by the number of years of exposure. The authors estimate* that for each extra 10-obese years, the risk of diabetes increased by 25%.


• Among 10,521 (94%) women who were not obese at baseline, the researchers observed that women who became obese during follow-up had a 3-fold increased risk of T2D compared to women who remained not obese.


• Compared with women who did not become obese during the follow-up, women who became obese and had obese-years of <10, 10 to under 30, and 30 or more had increased risks of developing T2D of two, three and six times, respectively.


• Results of analysis using only the women's initial (baseline) BMI found that having baseline obesity (a BMI of 30 or more) was associated with a 7-times increased risk of developing diabetes, while overweight women (BMI 25.0 to 29.9) had a 2.3 times increased risk compared with women with normal weight.


• Analyzing how the women's BMI developed through the study, those who were already obese at baseline, but who continued to put on weight rapidly on top of this had 10-times increased risk of developing diabetes compared with normal-weight women who remained stable; women who were overweight (rather than obese) at baseline, and who put on weight rapidly, had a 5-times increased risk of diabetes compared to the normal-weight women who remained stable.


• Further analysis of adjusting the data for the number of children, dietary intake (including total energy intake), fiber intake, and dietary glycaemic index (how foods with different carbohydrate composition affect blood glucose levels) gave similar results.

The authors say: "More than half of the women experienced a rapid BMI increase from early (18-23 years old) to middle adulthood (37-42 years old). Our data confirmed that BMI in young adulthood played an important role in the subsequent risk of developing type 2 diabetes during adulthood. We also observed that women who were non-obese at baseline but became obese during follow-up had a higher risk of type 2 diabetes relative to women who stayed non-obese; the younger the age at onset of obesity or the greater the obese-years, the higher the risk of type 2 diabetes."

They add: "Our data also indicated that baseline BMI among young women was significantly associated with risk of developing type 2 diabetes.The results highlight the importance of overweight or obesity in early adulthood as risk factors for adult diabetes, indicating that weight control starting before early adulthood is critical for reducing type 2 diabetes risk in later life."

They conclude their work demonstrates "the importance of preventing or delaying the onset of obesity and reducing cumulative exposure to obesity to substantially lower the risk of developing diabetes. We recommend that people self-monitor weight change over time, and that health care providers look at weight change in addition to current weight as another risk factor for diabetes."

The study, "Age of obesity onset, cumulative obesity exposure over early adulthood and risk of type 2 diabetes," is published in the Diabetologia journal.

DOI: https://doi.org/10.1007/s00125-019-05058-7