The causes of diabetes are complex and only partly understood. Complicating the picture even further is the fact that there are multiple types, each with its own risk factors. Type 1 and Type 2 diabetes are the most common, encompassing about 97% or more of cases in the U.S. Each results from a combination of environmental and genetic influences.

Of those, Type 2 is far and away the most common, about 90% of cases.

Obesity is thought to be a major contributor to Type 2 diabetes. Being overweight is a good prototype for a cause since it is itself a combination of genetic background and lifestyle choices. Though the diet opted for and the amount of exercise one chooses to undertake are lifestyle choices, it's still true that some individuals gain or shed weight more easily than others.

Obesity and genetics are not the only factors for diabetes.

While diabetes that develops during pregnancy (gestational diabetes), ceases after delivery, it is a risk factor for developing Type 2 diabetes later in life. Nearly 40 % of women who have gestational diabetes will develop Type 2 diabetes, usually within ten years of the pregnancy in which the gestational diabetes occurred. Giving birth to a larger baby is another sign of high risk.

An intolerance of glucose is another factor influenced by genetics. It is logical that glucose intolerance is a contributing factor to Type 2, because this form of diabetes stems from an insufficient use of insulin, rather than a lack of insulin (like Type 1). It is strange that glucose intolerance exists, because glucose in the body's major energy source. Abnormal genes can make strange situations.

Ethnicity plays a role in whether or not an individual will develop Type 2 diabetes, though the reasons are not fully understood. Even after adjusting for lifestyle, Aboriginals, Africans, Latin Americans and some Asian groups are at higher risk. The profile varies between 1.5-2 times the incidence among Caucasians, according to one broad Canadian study. Oddly, though, the risk of Type 1 diabetes is much higher among Caucasians than any other race.

Having high blood pressure raises the odds, too. That again is partly a lifestyle (chiefly, diet and exercise) choice but it has a strong genetic aspect as well. There's a strong correlation between those with high blood pressure and those who will develop diabetes. Similarly, high cholesterol levels increase the risk. Over 40% of those with diabetes have higher than average levels of cholesterol in the blood.

But simple family medical circumstance is probably the largest genetic risk factor.

An individual with a parent or sibling who has Type 1 diabetes has him or herself a risk 10-20 times higher than average. For a newborn baby with a parent who has Type 1 diabetes the odds are 1 in 25, or 4% if the mother gives birth before age 25. Over age 25, the risk is 1%, about the same as the general population. The odds rise again to about 10% if either parent contracted diabetes before age 11.

Researchers are diligently studying the genetic risk factors for diabetes. In the past there was little that could be done to prevent these risks. Someday soon, genetic treatments may prevent genetic diabetes.