Diabetes has now reached epidemic proportions on a global scale. The estimated worldwide prevalence of adults with diabetes increased from 108 million in 1980 to 422 million in 2014 (ref. 1). As most (85–95%) cases of diabetes in adults are type 2, this observed rise in diabetes prevalence is quite likely due to increases in type 2 diabetes. In the United States alone, the direct and indirect costs of diabetes in 2017 were estimated to be $327 billion2. Moreover, diabetes and its complications now account for more than 2 million yearly deaths3.

A well-established observation is that obesity is a major driver for the rising prevalence of type 2 diabetes and other noncommunicable diseases in adults4. Although prospective diabetes prevention studies such as the Da Qing IGT and Diabetes Study, the Finnish Diabetes Study, and the Diabetes Prevention Program (DPP) have all demonstrated that lifestyle changes leading to significant weight loss can decrease the risk for the development of diabetes5,6,7, widespread intensive programs that provide durable weight loss have been difficult to achieve. Thus, it seems advisable to promote a healthy lifestyle early in life, as overweight and obesity in childhood persists into adulthood8. In addition, a better understanding of the reversibility of childhood overweight and obesity on the risk for type 2 diabetes would help guide the timing and utility of such interventions. A recent New England Journal of Medicine article presented data in men indicating that remission of overweight before the age of 13 years could lower the risk of type 2 diabetes in adulthood9.

Bjerregaard et al.9 used the Copenhagen School Health Record Register (CSHRR), which contains information on almost all children attending school in Copenhagen born from 1930 through 1989. For the same individuals, inpatient and outpatient diagnoses of type 2 diabetes were obtained from the National Patient Register that contains discharge diagnoses from hospitals since 1977 and from outpatient and emergency departments since 1995. They were thus able to analyze in a retrospective cohort of Danish men the various levels of risk for the diagnosis of type 2 diabetes at age 30–60 and link those to measurements of overweight from age 7 to early adulthood9. They set the criteria for follow-up in their analysis to minimize type 1 diabetes diagnoses and ended the follow-up on the date of a type 2 diabetes diagnosis, death, emigration, loss to follow-up, or 31 December 2015, whichever came first. They defined overweight and obesity on the basis of the Centers for Disease Control and Prevention (CDC) age- and sex-specific criteria.

There were 62,565 men included in the study, and 6,710 (10.7%) were classified with type 2 diabetes. Overweight at any age after 7 years was positively associated with the risk of type 2 diabetes in adulthood, and men who had been overweight in early adulthood (17–26 years of age) had the highest risk of type 2 diabetes. Men who were overweight at 7 years of age but had remission of overweight by 13 years of age and had remained at a normal weight during early adulthood had a risk of type 2 diabetes similar to those who had never been overweight (Fig. 1). Men who had been overweight only at 13 years of age or at 7 and 13 years of age had a risk of type 2 diabetes lower than those who had been persistently overweight but higher than those who had never been overweight. Men who had been overweight at 13 years of age and whose overweight had persisted into early adulthood had a risk of type 2 diabetes that was similar to those who had been overweight from 7 years of age onwards.

Fig. 1: Overweight at different ages and remission of overweight correspond with type 2 diabetes risk.
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Bjerregaard et al.9 used Copenhagen School Health records to track weights of men at ages 7 and 13 and in young adulthood, classifying them as overweight (red circles) or normal weight (blue circles). They were able to link these data to longitudinal records to assess the development of type 2 diabetes at age 30–60 years and identify patterns between overweight and propensity to develop type 2 diabetes.

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Among the 2,872 men who had been overweight at 7 years of age, 1,023 (35.6%) remained overweight or had become obese by early adulthood, and 1,849 (64.4%) had remission of overweight by early adulthood. The effect of overweight during childhood on the risk of type 2 diabetes may be reversible, as men whose body mass index (BMI) had decreased to below the 75th percentile in early adulthood had risks of type 2 diabetes similar to those whose BMI had remained in the 25th to 49th percentiles throughout the study period. Compared to men who had been obese at all ages, those who reduced their BMI to overweight by early adulthood halved their risk of type 2 diabetes, and those who reduced their BMI into the normal range had even lower risks, indicating the positive correlation of BMI to diabetes risk (Fig. 1).

Although other studies have highlighted the importance of early growth patterns for both height and weight in the development of overweight and obesity, the time points that have been suggested to have a crucial impact on weight status in adulthood have been inconsistent—for example, weight gain as early as in the first week of life has been related to overweight and obesity in adulthood10. While early puberty has been associated with increased risk of obesity and some cardiometabolic disorders in women, this association is less clear in men. A meta-analysis reported that BMI in men was inversely associated with the timing of pubertal maturation in five of eight studies11. The effect of obesity and the subsequent insulin resistance may affect men and women differently, and how puberty modulates this relationship in the development of type 2 diabetes is unclear.

Although this study is a retrospective analysis, a clear strength is the long-term serial follow-up of a large cohort. However, the authors were unable to analyze growth patterns and BMI before the age of 7 years, and BMI at age 13 years may not correspond to puberty in all men. These data also came from participants who were born between 1939 and 1959, and the overall environment today is markedly different, with less physical activity and more availability of high-calorie foods. Moreover, the findings are not likely to be generalizable and applicable to women or other populations with a known higher diabetes risk. How remission of weight gain was achieved in those who were overweight and obese was also not addressed.

Future research may examine the effects of remission and overweight in other populations on future type 2 diabetes risk. For example, girls experience puberty at an earlier age compared to boys, and this may have implications on when to address excess weight in order to decrease future diabetes risk. These data from Bjerregaard et al.9 demonstrate that the timing of the presence of obesity, especially around puberty, may be an important factor in the development of type 2 diabetes later in life. Identifying children who may be at higher risk for diabetes and addressing weight gain at critical stages in growth may mitigate or even eliminate the increased diabetes risk associated with overweight and obesity in childhood.