The Diabetes Prevention Program (DPP) was the first nationwide U.S. study to examine whether type 2 diabetes could be prevented or delayed through diet and exercise or medication. Sponsored by the National Institutes of Health, the study involved more than 3,200 adults diagnosed with prediabetes.

Begun in 1995, the three-year study confirmed that people at high risk for type 2 diabetes could prevent or delay the onset of the condition by making important changes to diet and exercise. Metformin, an antidiabetic agent, also helped lower risk, but its effects were less dramatic than changes to lifestyle.

Thirty minutes a day of moderate exercise five times a week, combined with a 5 to 7 percent reduction in body weight, resulted in a 58 percent reduction in diabetes among participants. Diet and exercise demonstrated even greater benefits in patients 60 years and older.

The results prompted the study's monitoring board to end the trial a year early because the data had answered the research questions.

Scientists continue to mine new data from the DPP, such as recent findings that the eye disease diabetic retinopathy can affect people with prediabetes. With rates of obesity, prediabetes and type 2 diabetes soaring, the Diabetes Prevention Program remains relevant.

More than 20 million Americans have diabetes, according to the U.S. Centers for Disease Control and Prevention, and at least 41 million are estimated to have prediabetes. The prevalence of both conditions is expected to grow as the population ages and rates of obesity continue to rise.

The Diabetes Prevention Program (DPP) was the first nationwide U.S. study to examine whether either diet and exercise or metformin, an antidiabetic agent, could prevent or delay the onset of type 2 diabetes in people with prediabetes. Prediabetes, also called impaired fasting glucose and/or impaired glucose tolerance, is a condition in which glucose (blood sugar) levels are higher than normal, but not high enough for a diagnosis of diabetes.

Sponsored by the federal government’s National Institutes of Health (NIH), the three-year study was launched in 1995. It was conducted on 3,234 people, at 27 medical centers around the country. The ages of the participants ranged from 25 to 85, with an average age of 51.

All of the participants were overweight or obese and had prediabetes. These conditions are risk factors for developing type 2 diabetes.

Nearly half of the participants were from minority populations that have an increased risk of developing type 2 diabetes. The racial and ethnic makeup was:

• White, 55 percent
• African American, 20 percent
• Hispanic/Latino, 16 percent
• American Indian, 5 percent
• Asian American/Pacific Islander, 4 percent

However, only 32 percent of the subjects were men. Men account for 53 percent of the estimated 20.8 million cases of diabetes in American adults, according to the NIDDK.

The participants were randomly divided into four groups.

The participants were then randomly divided into four groups:

• The first group was given intensive counseling on effective diet, exercise and behavior modification. By eating less fat and fewer calories and moderately exercising for 150 minutes a week, this group’s goal was to lose 7 percent of body weight and to maintain the loss. 
  
  
• The second group took an 850-milligram dose of metformin (see Biguanides) twice a day. Members also received information on diet and exercise but no intensive counseling.
  
  
• The third group took placebos (pills that have no effect) instead of the metformin. Like the second group, members also received information on diet and exercise but no intensive counseling.
  
  
• The fourth group was given the insulin-sensitizing medication troglitazone, a type of thiazolidinedione. This part of the study was discontinued in 1998 upon the discovery that troglitazone could seriously damage the liver.

Researchers continued to assess the 585 volunteers who had taken the medication. The NIH announced in 2005 that, according to a new analysis of data from the DPP, among those who had taken troglitazone - for an average time of less than 11 months – the rate of diabetes was 75 percent lower than among those who had taken a placebo. The scientists concluded that this development showed the value of treating insulin resistance to help prevent type 2 diabetes.

The Diabetes Prevention Program (DPP) ended a year early because the findings clearly answered the question of whether type 2 diabetes can be delayed or prevented through diet and exercise or medication. The results were published in February 2002 in the New England Journal of Medicine. Among the findings:

• Members of the first group, who received intensive counseling on making lifestyle changes, reduced their risk of developing type 2 diabetes by 58 percent. Participants who were age 60 and older reduced their risk by 71 percent. About 4.8 percent of the group developed diabetes each year during the study. On average, the participants achieved their weight goal, an average loss of 7 percent (15 pounds), in the first year of the study and maintained a 5 percent total loss for the duration of the study.
  
  
• People in the second group, who took the drug metformin, reduced their risk of developing type 2 diabetes by 31 percent. This treatment was most effective in participants age 25 to 44 and in obese people with a body mass index of 35 or higher. About 7.8 percent of the group developed diabetes each year during the study.

A follow-up study released in 2006 indicated that participants taking metformin were 38 percent less likely than those taking a placebo to become diabetic.

• In the third group, who took the placebos (pills that have no effect), 11 percent of the participants developed diabetes each year during the study.

The DPP showed that moderate weight loss and regular exercise can prevent or delay the onset of type 2 diabetes. It also showed metformin to be effective in delaying the onset of the disease, although the reduction was significantly less.

The findings are considered significant because they offer the millions of people at high risk of developing diabetes a way to significantly reduce their risk – a moderate weight loss of 5 to 7 percent body weight (10 to 15 pounds), achieved through healthier eating habits and 30 minutes of exercise five days a week.

Weight loss and exercise reduce a person’s risk of diabetes by improving the body’s ability to use insulin and manage glucose (blood sugar). They also reduce the risk of heart conditions, stroke, some forms of cancer and many other health problems.

Researchers continue to analyze data from the Diabetes Prevention Program (DPP) for more information on the roles of diet and exercise and metformin in preventing type 2 diabetes. Researchers are also still monitoring participants to learn more about the study’s long-term effects. For example:

• A new analysis revealed in 2005 that the eye disease diabetic retinopathy had been detected in nearly 8 percent of the prediabetic participants and 12 percent of subjects who became diabetic during the three-year DPP.

• A follow-up study released in 2006 found antidepressants to be a risk factor for diabetes. Some studies have shown depression to be more common in people with diabetes or prediabetes, and researchers are cautioning that the benefits of antidepressants can outweigh the risks. Patients taking antidepressants may be advised to have glucose tests more often or to begin early treatment with medication or other interventions.

• Women in the DPP lifestyle intervention group (weight loss through diet and exercise) had less risk of urinary incontinence than those in the metformin or placebo groups, researchers reported in 2006. 

Other analyses will attempt to:

• Determine the separate contributions of diet and exercise to the reduction in diabetes.
  
  
• Determine the effect of metformin and diet and exercise on the development of cardiovascular diseases, such as atherosclerosis, diabetic angiopathy and coronary artery disease.

In addition, the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) is encouraging new research to explore cost–effective methods of providing lifestyle modifications in group settings and over the Internet, as well as methods to maintain behavior changes and weight loss.

Follow-up projects include the Diabetes Prevention Program Outcome Study (DDPOS) and the Look AHEAD (Action for Health in Diabetes) study of how diet and exercise affect cardiovascular disease in people with type 2 diabetes. The agency is seeking to build on the DPP with major new studies of diabetes in children.

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about the Diabetes Prevention Program (DPP):

1. What implications does the DPP have in management of my diabetes?
   
   
2. Does the DPP have any implications in reducing my risk of diabetic complications such as cardiovascular disease or diabetic retinopathy?
   
   
3. Can improved exercise habits reduce my need for medication?
   
   
4. Can an improved diet reduce my need for medication?
   
   
5. If I’m prediabetic, should I take metformin to prevent or delay diabetes?
   
   
6. Have follow-up studies compared metformin to other antidiabetic agents?
   
   
7. What do the follow-up study’s findings about antidepressants mean for me?
   
   
8. Does the DPP show how my loved ones can reduce their risk of becoming diabetic?
   
   
9. How do the latest analyses of data from the DPP affect me?
   
   
10. What other major diabetes research projects should I be aware of and follow?
    
    
11. How can I participate in projects such as the DPP?