So what IS diabetes anyways?... How did Santa and the other 10% of the world get it?
Let's break it down.

Diabetes is a disease of improper insulin functioning. It is characterized by 2 main forms:
Type 1: The body cannot produce insulin.
Type 2: The body has become resistant to insulin (cells cannot use it).
90% of people with diabetes (along with Santa) have Type 2. Unlike Type 1, Type 2 is entirely preventable and mostly reversible.
So what is Santa doing wrong?
The main problem with sugar is that our bodies are not evolved to metabolize it in large proportions; especially without the accompaniment of natural fibers (like you would find in whole fruits and vegetables) that slow down digestion.
2. Santa Eats Unhealthy Types of Dietary Fats
One of the ways our bodies use the fats we eat is to construct cell membranes. These are the outer layers that surround and protect our cells. They determine what nutrients get in and what waste products get out. If the membranes are made up of shoddy materials, they don't function as well (i.e. sugar is less able to enter cells).
The standard American diet is loaded with these shoddy materials in the form of highly processed vegetable and seed oils (corn oil, soybean oil, canola oil, sunflower oil, safflower oil, etc). These oils are pro-inflammatory and prone to oxidation.
For a more in-depth analysis of which fats to eat and which to avoid; here's a solid breakdown from Chris Kresser's blog.
3. Santa is a Gluten Junkie
When a person becomes insulin resistant at the cellular level, the pancreas compensates by pumping out more insulin into the bloodstream. And since insulin is in essence a storing hormone, this creates a perfect environment for fat gain.
On the other hand, when a person gains excessive amounts of fat, it put's stress on the organs and the individual cells to keep up. Our metabolic pathways start to resist and break down.
Skinny Diabetics
Recent studies even suggest that skinny people with diabetes are actually at a greater risk for developing commodities like heart failure and chronic kidney disease. This makes sense when you consider that the fundamental process of storing body fat is protective. The whole reason our bodies take sugar and turn it into fat is so that it doesn't hang around in the blood too long.
Alright you cotton-headed-ninny-muggins- I know that it's Christmas... And that's no time to go on a diet. But the new year is upon us. Let's all join Santa in eating a little less sugar, a little less seed oils, and a little less bread... So we can all be a little less diabetic this next year.
Tight Junctions, Intestinal Permeability, and Autoimmunity Celiac Disease and Type 1 Diabetes Paradigms
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2886850/
Gliadin induces an increase in intestinal permeability and zonulin release by binding to the chemokine receptor
http://www.ncbi.nlm.nih.gov/pubmed/18485912
Amylopectin starch promotes the development of insulin resistance in rats.
http://www.ncbi.nlm.nih.gov/pubmed/7782895
What is the Cause and Cure for Type 2 Diabetes
http://www.eidon.com/diabetes.html
Membrane Fatty Acid Transporters as Regulators of Lipid Metabolism: Implications for Metabolic Disease
http://physrev.physiology.org/content/90/1/367
How does Obesity cause Diabetes
http://life.gaiam.com/article/how-does-obesity-cause-diabetes
Obesity Paradox: Why Being Thin with Diabetes Is a Dangerous Combo
http://healthland.time.com/2012/08/08/obesity-paradox-why-being-thin-with-diabetes-is-a-dangerous-combo/