With support from the National Institute of Diabetes, Digestive and Kidney Diseases of the National Institutes of Health, a group of clinical investigators from around the United States developed a program with the goal of preventing diabetes and put that program to a scientific test. The Diabetes Prevention Program, or DPP as it was called, involved 3,234 people who did not have diabetes but who were at high risk for developing diabetes. The DPP was the largest study of lifestyle changes to prevent diabetes that has ever been conducted. The study participants were all adults (older than twenty-five) and overweight or obese, and they all had impaired glucose tolerance (IGT). IGT is a condition in which blood-sugar levels are elevated after a standardized test called the oral glucose tolerance test, but not high enough to be considered diabetic. People with this condition are on the road to developing diabetes, which is why IGT is now called prediabetes. The DPP volunteers were ethnically diverse, including approximately 50 percent Caucasians and 50 percent of the ethnic-racial groups at particularly high risk for diabetes such as African-Americans, Hispanic-Americans, Asian-Americans, Pacific Islanders, and American Indians.
The DPP was supported by grants from the government, the American Diabetes Association, and several companies that make products involved in treating diabetes.
The DPP lifestyle program was directed at achieving long-lasting changes in the behaviors that cause weight gain and a sedentary lifestyle. Although the goals of the lifestyle intervention were not intensive, the training to change the ingrained behaviors of a lifetime was intensive. The people assigned to the lifestyle intervention group were asked to lose 7 percent of their l33
initial weight. This amounted to an average of only fifteen pounds per person. In addition, they were asked to be more physically active, with 150 minutes per week of moderate-intensity activity. To achieve these goals, the lifestyle participants were given individual teaching with a core curriculum designed to retrain them in a lifestyle that would lead to weight loss and increased activity.
The DPP program was not a "one-size-fits-all" program. Instead, we worked with the people in the lifestyle intervention group of the study to find specific nutrition and exercise programs that would work for them. We identified and addressed specific barriers to changing behavior—whether it was shopping, cooking, eating, or physical activity. This comprehensive behavioral approach paid off. It resulted in sustained weight loss and increased activity levels that translated into fewer of these people developing diabetes. Some examples of the basic options of the DPP are presented in this book, so that we can provide you with the same information and options given to the people in the study. And we very much hope you'll experience the same success.
The specific lifestyle changes required to achieve the weight and activity goals were as varied as the population being studied; however, the major thrust was to decrease the amount of fat in the diet. This strategy was chosen because fat carries more calories per gram than carbohydrates or protein, and because it is relatively easy for a person to identify fatty foods and limit them. Program participants were taught to shop for, cook with, and eat less fat. The goal of increased physical activity was to help lose weight and maintain weight loss by increasing energy output. Exercise also was expected to prevent diabetes by increasing muscle sensitivity to insulin (as explained in Chapter 2).
The specific lifestyle goal related to activity was to perform moderate-intensity activity for at least thirty minutes per day, five days per week. Some of the DPP volunteers in the lifestyle group chose to participate in competitive sports, ballroom dancing, or 34, swimming, but for most of them, activity consisted of brisk-
paced walking. This could be done outside, in malls, at lunch hour, while walking the dog or pushing a stroller, or after dinner.
This program worked: most people reduced fat, and therefore calories in their diet, exercised for an average of thirty minutes per day, lost weight (an average of fifteen pounds), and kept most of it off during the three years of the study. Most important, lifestyle intervention was effective in preventing diabetes. The people in the lifestyle intervention group were 58 percent less likely to develop diabetes over a three-year period than the people in the control group. In the United States, if these results were applied to the population at high risk to develop diabetes (such as those recruited into the DPP), which is more than ten million people, this would reduce the annual occurrence of new diabetes cases from 800,000 to fewer than 400,000 cases per year.
Because the DPP combined both diet and exercise changes, we could not measure the effects of diet alone or exercise alone. However, other analyses of the results of the study indicate that the changes in diet that resulted in weight loss had a dominant role in preventing diabetes, while the exercise program was important in sustaining the weight loss.
So, by addressing the lifestyle changes that have contributed to the development of diabetes, the DPP showed that diabetes can be prevented—it is not inevitable. The results from two smaller but similar studies conducted in China and Finland have shown similar results as the DPP. These studies—conducted in different societies among people with different lifestyles and genetic makeup—emphasize that the DPP's message is universal: lifestyle changes work in preventing diabetes.
We will talk more about the DPP in subsequent chapters.
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