Sept. 26, 2003 -- The obesity epidemic is widely blamed for a startling rise in the incidence of type 2 diabetes among children. Intriguing new research suggests it is also to blame for a similar increase in type 1 diabetes.
Though being overweight is the main risk factor for developing type 2 diabetes, it has not previously been thought to be a major factor in type 1 diabetes, once known as "juvenile-onset diabetes." Type 1 diabetes is considered to be a genetically driven autoimmune disorder in which the body destroys the insulin-producing cells that allow it to process glucose. In type 2 diabetes, the body produces insulin but is unable to use it properly, a condition known as insulin resistance.
In a hypothesis first made public two years ago, U.K. researcher Terry Wilkin, MD, and colleagues suggested that type 1 diabetes and type 2 diabetes are "one and the same disorder of insulin resistance set against different genetic backgrounds." To prove this, the researchers recently examined the relationship between body weight and age at diagnosis among a group of children with type 1 diabetes.
Ninety-four children between the ages of 1 and 16 were included in the study, and a strong correlation was seen between the children's age at the time diabetes was diagnosed and their weight. The findings are published in the October issue of the American Diabetes Association journal Diabetes Care.
"Basically, the age (at diagnosis) got younger and younger as the children got heavier and heavier," Wilkin tells WebMD. "This doesn't prove that insulin resistance drives type 1 diabetes, but it is some of the first direct evidence suggesting that it plays a role."
Wilkins says the observation could explain why more and more children are developing type 1 diabetes and why they are doing so at earlier ages than ever before. Kids who develop type 1 diabetes are genetically predisposed to get the disease, but being overweight accelerates the process, he argues.
Two other studies published in the same issue of Diabetes Care lend credibility to Wilkin's hypothesis. Researchers Ingrid M. Libman, MD, PhD, Dorothy J. Becker, MBBCH, and colleagues recorded the incidence of being overweight in children with type 1 diabetes treated at the Children's Hospital of Pittsburgh during two time periods.
Three times as many children diagnosed during the 1990s were considered overweight as those diagnosed in the 1980s. In a separate study, the researchers found that one in 10 of the white children they studied and one in four of the black children had both the genetic predisposition that defines type 1 diabetes and the insulin resistance associated with type 2 disease. The researchers refer to the phenomenon as "double diabetes."
"It is too simple to look at a child with diabetes and say they are overweight so they have type 2 disease or they have autoimmunity so they have type 1 disease," Libman tells WebMD. "There seems to be more and more overlap between the two, especially among black children."
American Diabetes Association spokesman Robert Rizza, MD, tells WebMD that though the studies provide some of the first clinical evidence that obesity plays a role in type 1 diabetes, the idea is not new.
"These articles provide evidence for what a lot of people have suspected," he says. "They also suggest the possibility that obesity may trigger type 1 diabetes in some [genetically predisposed] people who would never get the disease. That is pure speculation at this point, but it is possible."