Diabetes is a chronic disease that is caused by the body’s inability to use glucose (blood sugar) properly due to a lack of or defects in insulin production. The precise cause of this insulin malfunction isn’t entirely understood, but genetic and environmental factors come into play. Additional contributing factors include inactivity and obesity. Specific causes include the following:

Lack of Insulin

This is specific to type 1 diabetes. It occurs when insulin-producing beta-cells are damaged or destroyed and stop producing insulin. Insulin is needed to move blood sugar into cells throughout the body. The resulting insulin deficiency leads to elevated glucose in the blood and prevents the body from being fueled properly.

Insulin Resistance

This is specific to type 2 diabetes. It occurs when insulin is produced normally in the pancreas, but the body is unable to use it properly and move it into the cells for fuel. At first, the beta cells will produce more insulin in an attempt to overcome the body’s resistance to it, but over time, the cells will eventually “wear out.” At that point the body decreases its insulin production, which leads to elevated glucose levels in the blood.

Pregnancy

A small percentage—studies show less than eight percent—of pregnant women may develop gestational diabetes. Hormones developed in the placenta interfere with the body’s normal insulin response and lead to insulin resistance and high levels of glucose in the blood.

Genetics

Inherited risk factors are believed to be a factor in causing all types of diabetes, but because most people with these risk factors do not develop the disease, researchers believe environmental triggers—diet and even climate—may also play a role. Genetics are believed to play an even stronger role in type 2 diabetes, in which family history is one of the leading factors. At the same time, type 2 diabetes also has a stronger environmental basis than type 1 diabetes. In other words, a family history of type 2 diabetes is a hugely important risk factor, but only in western cultures where high-fat diets and sedentary lifestyles are common. People living in non-western cultures rarely develop type 2 diabetes, no matter what their genetic risk.