More people than ever before have diabetes. And that’s not just because there are more people than ever before.

According to the Centers for Disease Control and Prevention, in 1988 approximately 2.5% of American adults had diagnosed diabetes. Today that figure is over 7%, which represents approximately 23 million men and women. Add the 7 million adults with undiagnosed cases and the number of people with diabetes in this country approaches 10% of the total population.

“Diabetes is a major public health threat, not just in our country but globally,” said Alain Bertoni, MD, professor and chair of epidemiology and prevention in the Division of Public Health Sciences at Wake Forest School of Medicine. “It’s a chronic, long-term disease with complications that cause a lot of serious problems and require a lot of resources.”

Diabetes occurs when blood glucose levels are too high because the body cannot produce insulin (type 1) or properly use it (type 2) to process sugars from food. Type 2, formerly known as adult-onset diabetes, is by far the most common, representing about 90% of all cases.

Diabetes is debilitating in its own right but if left untreated it can lead to many severe conditions, including heart disease, stroke, kidney failure, high blood pressure, blindness and the loss of toes, feet and legs. It is also the seventh-leading cause of death in the US.

Though the rate of new cases has declined somewhat in the past decade, type 2 diabetes isn’t going anywhere: Around 1.5 million people are diagnosed with the disease each year.

Plus, an estimated 84 million American adults have prediabetes, a largely undiagnosed condition where blood sugar levels are above normal but below the threshold for type 2. Over time it develops into full-blown diabetes in about 70 percent of cases.

So why is type 2 diabetes more common than ever before?

Obesity is often cited as the culprit. And with good reason.

The percentage of Americans who are obese has jumped from around 15% in late 1980s to approximately 33% today. (Another one-third of the population is said to be overweight.) More than 80% of diabetics are obese or overweight, and diabetes and obesity afflict so many people at the same time that there’s a term for their coexistence: diabesity.

“The increase in diabetes in our society is almost certainly driven by the increase in obesity,” Bertoni said. “But not everybody who has diabetes is obese and not everybody who is obese has diabetes. There are definitely other factors at work.”

A family history of type 2 diabetes is one of the known risk factors for the disease and its complications. So is age; people over 65 are six times more likely to get diabetes than those 18 to 44.

Some risk factors are physical conditions, including abdominal obesity, high blood pressure and elevated levels of LDL (“bad”) cholesterol and blood glucose. Others are lifestyle choices, such as high-calorie diets, lack of exercise and smoking. And still others are societal in nature.

“People do have responsibility for the choices they make, but not all of those choices are 100% under their control,” Bertoni said. “There’s poverty, for example. If you’re poor in this country you’re more likely to develop diabetes than someone of higher economic status. And if you’re any minority—African-American, Hispanic, Native American, Asian—you have a higher risk than whites. Some of that is thought to be genetic, but socioeconomic factors are also involved.”

Research has shown that education level, occupation and modes of transportation can influence an individual’s likelihood of getting diabetes. There’s also evidence that the number of food resources (grocery stores, restaurants) and physical activity venues (parks, recreation centers, even sidewalks) near one’s home can have an impact.

One of the problems public health researchers like Bertoni have is determining how much each of the various factors independently contribute to the development of diabetes, largely because the disease seldom exists by itself.

“It’s almost impossible to find someone who has just diabetes,” he said. “Most people with diabetes also have one or more other risk factors, which complicates things.”

But none of this means that individuals can’t take steps to lower their odds of developing the disease.

“We have clinical trial and observational evidence that the risk of getting diabetes can be greatly reduced, even in high-risk individuals,” Bertoni said. “What people can do is control the things they can control.

“Number one is maintaining a healthy weight. If you’re already overweight or obese you should try for modest weight loss, preferably 10 percent of your current weight. Number two is physical activity, about 150 minutes a week at a decent level of intensity, one that you can handle. When done together these work better than any drug.”