THE EARLIEST DOCTORS to discover diabetes knew it as an exceptionally rare disease. Physicians today see it all too often. While our society’s ever-growing girth has played a role in that, there’s more to the story, according to Dan Hurley, author of “Diabetes Rising” ($26.95, Kaplan).

Namely, that it’s not just type 2 diabetes, the kind usually found in overweight, sedentary adults, that’s increasing. It’s also type 1 diabetes, the kind Hurley has, which strikes children seemingly at random and becomes a chronic condition.

There’s also the mystery of why the medical community is so helpless to stop this upswing. “Cancer is slowly declining, and heart disease is going down,” Hurley rattles off. But diabetes is a bigger problem than ever. And it comes with the biggest question of why.

Option one is “the accelerator hypothesis.” “People are growing faster, bigger and taller,” Hurley says, and there’s evidence that points to size acting as a trigger for both forms of diabetes. Even most healthy kids today are larger than their ancestors were, simply because of less childhood disease and better access to proper nutrition. While type 1 is often known as “skinny diabetes,” data show that young people who get it are often slightly bigger than their peers.

Another possibility is that the increase is being caused by lack of vitamin D. A majority of kids aren’t getting enough of it, and epidemiological research indicates a connection between deficiencies and an increased rate of diabetes. Hurley points to the anecdote he relates in the start of his book, about alarmingly large clusters of kids in the Boston suburbs being diagnosed with type 1. “These clusters can easily appear by chance. That said, there’s not a lot of sunshine there,” he adds.

Hurley also thinks there’s something to the idea that feeding infants foreign proteins, such as cow’s milk, could be the trigger. So, he and his wife used only hydrolyzed formula, which breaks the proteins down, for their daughter. There’s also some evidence that indicates persistent organic pollutants (such as BPA) could be the cause, or maybe the rise in good hygiene.

As research continues, Hurley thinks there will finally be a definitive answer to help society fight this surge. He just hopes it happens soon.