Obesity is an excess of body fat. It is one of the leading causes of preventable death, contributing to serious health problems such as diabetes, heart disease and cancer.

Obesity has traditionally been measured with body mass index (BMI), a calculation based on an individual’s weight and height. However, waist-to-hip ratio and waist measurement may provide more useful information.

The connection between excessive weight and the risk for prediabetes and diabetes is well documented. More than 85 percent of people who develop type 2 diabetes are considered overweight or obese, according to the Centers for Disease Control and Prevention (CDC).

Excess weight also increases pregnant women’s risk of developing gestational diabetes. In addition, people with type 1 diabetes who become overweight can develop insulin resistance, a condition known as double diabetes.

Furthermore, obesity increases the risk of many diabetic complications, including heart conditions, stroke, kidney disease and eye disease.

Excessive weight has reached epidemic levels in the United States. About one-third of American adults are obese and an additional one-third are overweight, according to federal health agencies. Rising rates of obesity in America and worldwide are fueling a global increase in diabetes.

Poor diet and lack of exercise are the main causes of obesity, but many other factors may be involved as well, such as genetics, prior health problems, age, culture and medications. Reducing obesity plays a central role in preventing or managing type 2 diabetes. In some cases weight-loss surgery has resolved cases of type 2 diabetes. In addition, some newer diabetes treatments have shown promise in fighting obesity.