The pancreatic cells that produce insulin can be destroyed in overweight teens as well as adults, requiring injections of insulin, according to new Sheba study.
For many years, diabetologists have been saying that the main difference between type 1 and type 2 diabetes is that the first is a genetic, autoimmune condition that usually shows up early in life, and type 2, referred to as “adult onset,” is mainly related to lifestyle problems and develops over time because the person is overweight and inactive.
What we thought we knew about diabetes
It was believed that type 1 diabetes, formerly described as “juvenile-onset,” results from the immune system attacking and destroying the insulin-producing cells in the pancreas, thus requiring that the patient inject himself regularly with lifesaving insulin. But the incidence of type 1 diabetes has been rising annually by about two to three – and the reasons why were not clear.
But new research conducted at Sheba Medical Center at Tel Hashomer and just published in the journal Diabetologia shows that an excessively high body mass index in adolescents is linked to the development of type 1 diabetes and not just the type 2 form.
The study, entitled “Obesity in late adolescence and incident type 1 diabetes in young adulthood,” was presented simultaneously with publication at the American Diabetes Association’s annual meeting now being held in New Orleans, Louisiana. It was led by Prof. Gilad Twig of Sheba’s internal medicine department who previously was a Google Scholar at the department of military medicine at the Hebrew University’s Faculty of Medicine 
What were the findings of the study?
Twig’s findings were based on IDF recruits. In this nationwide study, all Israeli adolescents aged 16- to 19-years-old who underwent medical evaluation in preparation for mandatory military conscription between January 1996 and December 2016 were included for analysis, unless they had a history of abnormal blood sugar. A total of 1.46 million adolescents were included. Weight and height were measured at study entry and statistical modeling used to calculate any excess risk of type 1 diabetes associated with overweight or obesity.
There were 777 new cases of type 1 diabetes during 15,819,750 person-years of follow-up (mean age at diagnosis 25 years). BMI was found to be linked with incident type 1 diabetes (new-onset diabetes in individuals without prevalent diabetes at baseline). In a model adjusted for age, sex and socio-demographic variables, the increased risk of type 1 diabetes increased as BMI increased.
About half of all cases of type 1 diabetes develop after age 18. By reputation, people think it’s a disease of children. But it’s begun to grow so that now, 50% of cases occur soon after late adolescence, said Twig. “Obesity is related to several other autoimmune conditions, so it’s not a complete surprise it might be related to another.”
A possible explanation the researchers gave was that the elevated levels of inflammatory adipokines and cytokines associated with obesity reduce tolerance by the immune system of tissues in the body by promoting inflammatory processes that lead to diabetes.
Twig and his team said that additional factors associated with obesity could contribute to the development of autoimmunity, including vitamin D deficiency, consumption of a high-fat diet and changes in the bacteria in the gut. Various biological mechanisms have been suggested to explain the connection between obesity and type 1 diabetes.
The “accelerator” hypothesis maintains that both type 1 and type 2 diabetes are caused by insulin resistance set against various genetic backgrounds that affect the rate of loss of the insulin-producing beta cells in the pancreas. According to this hypothesis, the increasing demand for insulin makes the beta cells more prone to destruction by the immune system and thus speeds up their loss.
What are the implications?
The authors declared that their findings have important public health implications.
The prevalence of adolescent obesity is rising worldwide at an alarming rate, with dire projections for the near future. Currently, it is estimated that nearly 60% of American children and teens aged two to 19 will develop obesity by age 35 years, most of them by adolescence, with half progressing to severe obesity.
“The current study projects that around one in eight (12.8%) of the newly diagnosed cases of type 1 in the study can be attributed to abnormally excessive weight [in] adolescence. Thus, with rising levels of obesity, especially that of the severe form, we may expect that the current annual rise in type 1 cases… will be even more pronounced,” they added.
Our study adds to the growing evidence regarding the health hazards associated with adolescent obesity. Not only is adolescent obesity correlated with adult-onset of type 2 diabetes, but also with type 1 diabetes.
Study authors, “Obesity in late adolescence and incident type 1 diabetes in young adulthood.”
“Further work needs to be done to unravel this association so that we can better address the full spectrum of risks posed by the obesity epidemic or identify common environmental factors affecting both weight and type 1 diabetes.”