"I understand why my father would not have wanted to consider the possibility that ice cream might have been involved. By this point he had manufactured and sold more ice cream than any human being who had ever lived on this planet. He didn't want to think that ice cream was harming anyone, much less that it might have contributed to the death of his beloved brother-in-law and partner. Besides, not much was commonly known then, in the late 1960s, about the connection between ice cream and disease.
But I saw the connection, as I did when my dad developed diabetes and high blood pressure, and again years later when Ben Cohen, co-founder of the ice cream company Ben & Jerry's, needed a quintuple bypass procedure at the age of forty-nine.
A single ice cream cone, of course, isn't going to harm anyone. But even though it tastes delicious, ice cream is very high in sugar and saturated fat. The medical data is overwhelmingly clear that the more sugar and saturated fat you eat, the more likely you are to experience heart disease and diabetes and to become obese."
http://www.openexchange.org/features/JFM10/robbins.html
Are you going to argue with the son of a ice cream maker?!
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"Causes of Diabetes
The cause of Type I diabetes is genetically based, coupled with an abnormal immune response.
The cause of Type II diabetes is unknown. Medical experts believe that Type II diabetes has a genetic component, but that other factors also put people at risk for the disease. These factors include:
sedentary lifestyle
obesity (weighing 20 percent above a healthy body weight)
advanced age
unhealthy diet
family history of diabetes
improper functioning of the pancreas
minority race (higher risk in Black, Hispanic, American Indian, westernized Asian and native Hawaiian populations)
medication (cortisone and some high blood pressure drugs)
women having given birth to a baby weighing more than 9 lbs.
previously diagnosed gestational diabetes
previously diagnosed IGT"
http://www.healthcentral.com/encyclopedia/408/150.html
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There isn't a known cause, but I personally believe, if you eat too much sugar for too long, the insulin in your body stops working (resistance builds up, kinda like alcohol tolerance) and bam, the definition of diabetes.