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As blogged previously, type 1 diabetes happens when the immune system attacks the cells in the pancreas that make insulin, and is therefore what we call an autoimmune disease. There is a genetic susceptibility to type 1 diabetes, but most often there is no family history of diabetes (though there is often a family history of other autoimmune conditions). We are not sure exactly what triggers type 1 diabetes, but many possibilities have been considered, including viruses or other environmental factors.     (This is very different from type 2 diabetes, which is tightly connected to elevated weight in most cases, with about 90% of people with type 2 diabetes carrying elevated weight.)

Could obesity be a risk factor for developing type 1 (autoimmune) diabetes?  A recent systematic review and meta-analysis summarizes available knowledge on this topic.

This review included 10 cohort studies of over 1.7million people with body mass index (BMI) data after the age of 2 years.  The mean or median age at study entrance ranged between 2-59 years, with some studies including only children and adolescents, some including only adults, and some including both.  The mean or median duration of follow up ranged between 1-20 years. Overall, their analysis reported a 35% increased risk of developing type 1 diabetes in children and adults with overweight (by BMI criteria), and an even higher 2.17 times increased risk for those with obesity.  For studies where type 1 diabetes was verified with antibody testing, the risk of developing type 1 diabetes was overall 2.55 times higher in people with overweight/obesity.  In populations with an average risk of developing type 1 diabetes, the relative risk for developing type 1 diabetes in people with elevated weight was even higher (2.1 x greater) than in genetically high risk populations (38% higher risk) (both compared to people with healthy weight).

How could elevated weight predispose to type 1 diabetes? We are not exactly sure, but several mechanisms have been proposed. The ‘accelerator hypothesis’ suggests that overweight and obesity, causing insulin resistance, stresses the pancreas to produce more insulin, leading to earlier failure of the insulin producing beta cells of the pancreas.  These beta cells working harder may release proteins that attract immune cells and drive the autoimmune disease process of type 1 diabetes. Obesity is also known to be a low grade inflammatory state, and these inflammatory hormones may also drive these processes.  Fat can actually accumulate directly in the pancreas in obesity, called ectopic fat (similar to fatty liver), putting inflammatory fat into direct contact with the beta cells.  Leptin, which is a hormone that is higher in people with elevated weight, has been shown to accelerate beta cell distruction, and adiponectin, which is lower in people with obesity, has been shown to protect beta cells from death. Other factors related to obesity, like changes in gut bacteria, and low vitamin D, have also been hypothesized to play a role.

These findings underline the importance of maintaining a healthy weight as a modifiable risk factor for development of type 1 diabetes.  As elevated weight can promote the development of cardiovascular complications of diabetes, weight management in people with type 1 diabetes and overweight/obesity at any age is of great importance.

For more on weight management in type 1 diabetes, check out this blog post.

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