Obesity in childhood may be a risk factor for all types of adult diabetes

Child obesity is linked to increased risk of developing diabetes in adulthood, both autoimmune forms of diabetes and different forms of type 2 diabetes, a new study published in Diabetologia reports. The risk of developing the most insulin-resistant form of diabetes is, for example, three times as high in children with obesity.

Diabetes affects some seven per cent of the adult population and is one of the world's fasted growing diseases. It has traditionally been divided into two subgroups – type 1 and type 2 diabetes – but research suggests that this is a simplification.

In 2018, a Swedish study identified five subgroups of adult-onset diabetes, characterized by auto-immunity, severe insulin deficiency, serious insulin resistance, overweight and advanced age.

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One way the researchers say that the relevance of these subgroups can be highlighted is to examine if the influence of known risk factors for diabetes differs between the proposed diabetes types.

"Our study is one of the first attempts to find this out," says the study's first author Yuxia Wei, doctoral student at the Institute of Environmental Medicine. "Childhood obesity has been linked to several chronic diseases, but has never been studied in relation to the recently proposed diabetes subgroups."

The purpose of the present study was therefore to see if the effect of childhood obesity differs. The researchers used a method called Mendelian randomization, which uses genetic information to study the correlation between an environmental risk factor and disease risk while taking into account the impact of other risk factors.

Basing their analysis on genetic data from over 400,000 participants in a biobank called UK Biobank, the researchers compared children who considered themselves larger than other children with children who rated their weight as normal.

The results showed that overweight/obesity in childhood was linked to a 62 percent higher risk of autoimmune diabetes, a doubling of the risk of diabetes characterized by insulin deficiency, almost a tripling of the risk of the most insulin-resistant form of diabetes and a seven-times higher risk of the form of diabetes primarily characterized by overweight.

"Our analyses show that children who are larger than others are more likely to develop four of the five proposed new subgroups of adult-onset diabetes," says Wei. "In other words, obesity in childhood seems to be a risk factor in effectively all types of adult diabetes, with the exception of age-related diabetes. This underscores how important it is to prevent obesity in children since it can have lasting effects on their future health."

The study was a collaboration among researchers at Karolinska Institutet, Bristol University (UK) and Sun Yat-Sen University (China).