I've copied a few paragraphs from this page at blood sugar 101(
you did not eat your way to diabetes )
Don't fall for the toxic myth that you caused your diabetes by reckless overeating. While people with diabetes often are seriously overweight, there is accumulating evidence that their overweight is a symptom, not the cause of the process that leads to Type 2 Diabetes.
While people who have diabetes are often heavy, one out of five people diagnosed with diabetes are thin or normal weight. And though heavy people with diabetes are, indeed, likely to be insulin resistant,
the majority of people who are overweight will never develop diabetes. In fact, they will not develop diabetes though they are likely to be just as insulin resistant as those who do--or even more so.
The message that diabetes researchers in academic laboratories are coming up with about what really causes diabetes is quite different from what you read in the media. What they are finding is that to get Type 2 Diabetes you need to have some combination of a variety of already-identified genetic flaws which produce the syndrome that we call Type 2 Diabetes. This means that unless you have inherited abnormal genes or had your genes damaged by exposure to pesticides, plastics and other environmental toxins known to cause genetic damage, you can eat until you drop and never develop diabetes.
Long before a person develops diabetes, they go through a phase where they have what doctors called "impaired glucose tolerance." This means that after they eat a meal containing carbohydrates, their blood sugar rockets up and may stay high for an hour or two before dropping back to a normal level.
What most people don't know is that when blood sugar moves swiftly
up or down most people will experience intense hunger. The reasons for this are not completely clear. But what is certain is that this intense hunger caused by blood sugar swings can develop years before a person's blood sugar reaches the level where they'll be diagnosed as diabetic.
This relentless hunger, in fact, is often the very first diabetic symptom a person will experience, though most doctors do not recognize this hunger as a symptom. Instead, if you complain of experiencing intense hunger doctors may suggest you need an antidepressant or blame your weight gain, if you are female, on menopausal changes.
This relentless hunger caused by impaired glucose tolerance almost always leads to significant weight gain and an increase in insulin resistance. However, because it can take ten years between the time your blood sugar begins to rise steeply after meals and the time when your fasting blood sugar is abnormal enough for you to be diagnosed with diabetes, most people are, indeed, very fat at the time of diagnosis.