Just my 2 cents' worth.. you should differentiate the different
types of diabetes:
Type 1 Diabetics: insulin deficiency from the pancreas cells,
resulting in cells not being able to absorb the glucose in the
blood stream, leading to higher than normal levels of blood sugar
aka 'diabetes'. In Type 1 DM, calorie intake does not affect blood
sugar levels because the body cannot produce enough insulin for
cells to take in the glucose. Type 1 DM is sometimes also known as
child-onset diabetes (because it usually occurs in children, and
requires a lifetime injection of insulin to control blood sugar
levels).
Type 2 Diabetes: cell signaling regulation problem. In Type 2
diabetes, usually what happens in that the muscle and liver cells,
become "resistant", or faulty to insulin, resulting in high blood
glucose levels. In Type 2 DM, yes it is partly true that excess
caloric intake is a contributing factor to the onset of diabetes.
Type 2 diabetes is the most common type of blood sugar disorder in
the world.
Actually, there are other sub-sets of diabetes. For instance,
Gestational diabetes (GDM), adult onset diabetes etc with different
causes. Therefore, not all diabetes are due to excess caloric
intake (though over eating does contribute to the risks of getting
diabetes
)