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April 23, 2001
Type 2 Diabetes and Obesity: What's the Connection?

By Irene S. Levine, Ph.D.

illustration: Type 2 Diabetes and Obesity: What's the Connection?
Jason Stout

first letter two recent studies on type 2 diabetes provide such striking evidence about the link between this type of diabetes and obesity that the findings may motivate even the most committed couch potatoes to get up and exercise.

In a study involving data from the years 1990 to 1998, officials at the Centers for Disease Control and Prevention (CDC) found a staggering 70 percent increase in type 2 diabetes among Americans between the ages of 30 and 39. Researchers attributed the whopping increase to sedentary lifestyle and poor nutrition, which together have caused obesity rates to rise in the United States.

The question of why obesity leads to type 2 diabetes has long been a mystery, but now, scientists may finally have an answer. Researchers at the University of Pennsylvania School of Medicine recently reported the discovery of a hormone that may, for the first time, explain the molecular basis for the connection between diabetes and obesity.

Study one: alarming trends of obesity in the United States

Diabetes results in the failure of the body to either produce or properly use insulin, the hormone necessary to convert sugars, starches, and other foodstuffs into essential energy. This condition is commonly referred to as insulin resistance. When this malfunction occurs, the result is a buildup of glucose in the blood that can pose serious health problems.


Based on the findings of the two studies, it is more important than ever for Americans to examine the lifestyle factors that can place them at risk for type 2 diabetes.


The disease has three variations: gestational diabetes, occurring during pregnancy and usually disappearing afterward; type 1 diabetes, which occurs in young children and adolescents and is sometimes referred to as juvenile-onset diabetes; and type 2 diabetes, or adult-onset diabetes, whose risk factors include old age and obesity (see sidebar below). Type 2 is the most widespread of the three; gestational and type 1 diabetes account for only 7 to 15 percent of all diabetes cases in the United States

Underscoring the severity of the prevalence of type 2 diabetes, a CDC study last year revealed a startling 33 percent increase in the overall incidence of type 2 diabetes from 1990 to 1998. There was a 70 percent increase in those aged 30 to 39, a 40 percent increase in those aged 40 to 49, and a 31 percent increase in those aged 50 to 59.

Obesity as a Risk Factor for Diabetes

While the causes of diabetes are not precisely known, both genetic susceptibility and environmental factors are presumed to play a role. According to the National Diabetes Education Program's 2001 figures, several factors place individuals at risk for type 2 diabetes. These include:

  • Being older than 45
  • Being overweight
  • Having a close family member with diabetes
  • Having had diabetes during pregnancy
  • Being African American, Hispanic/Latino, Asian American or Pacific Islander, or Native American

Officials at the CDC also reported a striking 6 percent increase in 1999 in the prevalence of type 2 diabetes among American adults of all ages. This increase was observed in women and men of all ages, across all ethnic groups, at all educational levels, and across most of the United States.

The CDC faults a higher rate of obesity, which is one of the major risk factors for diabetes, as the main cause for the elevated numbers. Along with the CDC's diabetes figures, the prevalence of obesity in this country rose nearly 6 percent during the same study period.

Since there is a delay between the onset of obesity and the subsequent development of diabetes, the rising statistics indicate that more and more sufferers of type 2 diabetes will emerge as time passes. "This dramatic new evidence signals the unfolding of an epidemic in the United States," says Jeffrey Koplan, M.D., director of the CDC, in a press release. "With obesity on the rise, we can expect diabetes rates to increase sharply as a result. If these dangerous trends continue at the current rates, the impact on our nation's health and medical care costs in future years will be overwhelming."

Study two: new hormone found from animal models

Although more than 80 percent of diabetics are known to be obese, until recently there was no scientific explanation for the relationship between type 2 diabetes and obesity. The discovery of a new hormone, however, may provide the missing link between the two conditions.

In a series of experiments with mice, Claire Steppan, M.D., faculty member in the department of endocrinology at the University of Pennsylvania School of Medicine, and her colleagues discovered a hormone produced by fat cells; they dubbed the new hormone resistin, for resistance to insulin. Dr. Steppan and the other researchers showed that the amount of resistin in the bloodstream rose markedly in mice with both diet-induced and genetic forms of obesity. And resistin levels in the mice decreased with the administration of rosiglitazone, an antidiabetic drug.

Type 2 Diabetes: The Toll It Takes

Type 2 diabetes is the most common form of diabetes, affecting 90 to 95 percent of the 16 million Americans afflicted with the disease. In the past, type 2 diabetes was often called non-insulin-dependent diabetes or adult-onset diabetes. According to the CDC, approximately 800,000 new cases of diabetes are diagnosed each year; more than 720,000 of these are type 2.

As one of the leading causes of death and disability in the United States, diabetes takes an enormous toll on society, both socially and economically. Those with diabetes are at increased risk for serious medical complications -- including blindness, kidney failure, lower extremity amputation, and cardiovascular disease. These complications account for an estimated $98 billion annually in associated health care costs.

The scientists also administered an anti-resistin antibody to obese mice and were able to improve blood sugar and insulin action in these mice. In a related experiment with standard-weight mice, treatment with resistin interfered with glucose tolerance and insulin action.

If humans and mice are found to react similarly to levels of resistin, these findings could someday provide the basis for new medications for type 2 diabetes. But experts are cautious, pointing out that the study is preliminary. Since the effects of resistin on the body as a whole remain a mystery, more research is needed to explain the function of resistin as the link between obesity and type 2 diabetes.

The role of lifestyle

Based on the findings of the two studies, it is more important than ever for Americans to examine the lifestyle factors that can place them at risk for type 2 diabetes. Frank Vinicor, M.D., director of the CDC's diabetes program, explains that "maintaining healthy behavior such as controlling weight through nutrition and physical activity can help ease the burden of diabetes, and may actually prevent its onset."

So ask yourself: Are you sedentary? Do you get regular exercise? Are you overweight? Do you watch your diet? If you already have diabetes, are you working to improve your diet and increase your level of exercise to better manage the disease? Are you educated about diabetes?

Improvements to your lifestyle and greater knowledge about diabetes can help you to manage the condition, or even prevent it altogether. Isn't it time to get off the couch?

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