If there was ever an exercise study that got the attention of physicians and health care decision makers, it was the Diabetes Prevention Program (DPP). The aim of this 3-year, multicenter, randomized clinical trial was to determine whether lifestyle intervention (including exercise) or pharmacological therapy (metformin) would prevent or delay the onset of diabetes in high-risk individuals (DPP Research Group 1999). The incidence of type 2 diabetes decreased by 58 percent in the lifestyle group, compared with 31 percent in the metformin group (DPP Research Group 2002b).
This study ranks among the top three most influential exercise and lifestyle studies of the last decade. Addressing a large New York medical group in December 2002, Dr. Steve Haffner, perhaps the most renowned medical authority on diabetes research, stated that the DPP findings had made believers of scores of skeptical academic colleagues who had previously undervalued physical activity’s role in disease prevention.
All fitness professionals should take great pride in the outcomes of this study. More important, practical application of the DPP’s “toolbox” of exercise and lifestyle intervention methods can be immensely useful in helping fitness professionals organize a research-tested approach to working with obese and diabetes-prone clients.
The following is a summary of key DPP exercise and lifestyle components outlined in the December 2002 issue of Diabetes Care (DPP Research Group 2002a). Readers who wish a far more detailed description (hundreds of pages of resources and lifestyle utilities), please access the DPP study repository Web site at www.bsc.gwu.edu/dpp/manuals.htmlvdoc.
(Editor’s Note: For a review of safe practices and legal standards for training clients with diabetes, metabolic syndrome and other diseases, see “National Consensus Guidelines for Clients With Medical Conditions” by Ralph La Forge, MS, in the January 2002 issue of IDEA Health & Fitness Source.)
The Lifestyle Intervention
The DPP intensive lifestyle intervention program, called “Lifestyle Balance,” was developed by the University of Pittsburgh Medical Center’s DPP Lifestyle Resource Core. This team of experts included nutritionists, behavioral psychologists, exercise physiologists, nurses and physicians.
A total of 3,234 subjects took part in the DPP; the lifestyle group had 1,079 participants, 45 percent of whom were from racial and ethnic minorities. All participants at all centers worked toward the same weight loss and physical activity goals; however, individualization was permitted in the specific methods used to achieve the goals. The intervention was intentionally standardized by having all participants start by following a structured core curriculum. After that, the maintenance program—consisting of individual sessions, group classes, motivational campaigns and restart opportunities—was more flexible.
The two major goals of the lifestyle intervention focused on weight loss and physical activity.
The Two Major Lifestyle Goals
The Weight Loss Goal. The weight loss goal was to lose 7 percent of initial body weight and to maintain this weight loss throughout the trial. The decision to use 7 percent as the goal was based on epidemiological data and results of previous weight loss trials. Participants were encouraged to achieve the weight loss in the first 6 months of the DPP lifestyle intervention, since previous behavioral weight loss research had suggested that most individuals achieve their maximum weight loss within the first 20 to 24 weeks of a lifestyle intervention (Jeffrey et al. 1998). The recommended pace of weight loss was 1 to 2 pounds per week. Participants who wished to lose more than 7 percent of their baseline weight were encouraged to do so, as long as they continued to have a body mass index higher than 21.
To help participants achieve the 7 percent weight loss goal, they were taught behavioral strategies that would enable them to realize and maintain long-term changes in fat and calorie intake. Physical activity was seen as important for long-term maintenance of weight loss and also as a possible way to prevent diabetes, independent of weight loss. Weight loss medications were not used as part of the trial.
The Physical Activity Goal. The physical activity goal was selected to approximate an energy expenditure of at least 700 calories [kcal] per week from physical activities. For participants, the goal was described as at least 150 minutes of moderate physical activities similar in intensity to brisk walking.
This goal was considered achievable and likely to be beneficial in preventing diabetes, based on previous studies. (For example, in a study of 6,000 men followed for 14 years, each physical activity increase of 500 kcal per week reduced the age-adjusted risk of diabetes by 6 percent [Helmrich et al. 1991]). In addition, the DPP goal was similar to the newest public health recommendations (Pate et al. 1995) and the guidelines presented in the 1996 Surgeon General’s report on physical activity and health (Centers for Disease Control and Prevention 1996).
In summary, 150 minutes of moderate physical activity per week was chosen because evidence suggested that this was a feasible and effective goal that participants could maintain on a long-term basis.
The DPP lifestyle intervention stressed brisk walking as the means to achieve the activity goal, but participants were given examples of other activities that are usually equivalent in intensity to brisk walking, including aerobic dance, bicycle riding, skating and swimming. Participants were encouraged to distribute their activity throughout the week with a minimum frequency of three times per week and a minimum duration of 10 minutes per session. A maximum of 75 minutes of strength training could be applied toward the weekly goal. The importance of lifestyle activities such as using the stairs (instead of elevators), stretching and gardening was discussed; however, participants were instructed not to apply these types of activities toward the 150-minute total.
Participants at high risk for cardiovascular disease underwent an exercise tolerance test before starting the activity interventions. Sedentary individuals were told to increase their activity in 30-minute increments over 5 weeks. Those who were sufficiently active at baseline were not required to add further exercise but rather had the same weekly goal as everyone else. However, the 150-minute goal was stated as a minimum, and participants who wished to be more active were strongly encouraged in that desire, as long as there were no medical contraindications.
10,000 Steps Program
One of the DPP’s most effective motivational campaigns for exercise and one that can be very useful to personal trainers working with inactive, diabetes-prone clients was the “10,000 Steps” program. Participants were encouraged to wear simple, low-cost pedometers and graduate from an inactive lifestyle (~2,000-4,000 steps per day) to 10,000 steps per day over a 4-to-6-week period. That goal is roughly equivalent to 150 minutes per week of moderate exercise (in addition to the activities of daily living). As a general guide, a mile of walking at a moderate pace is 2,000 to 2,200 steps for most adults. Ten thousand steps would be roughly equivalent to 4 or 5 miles of walking, although there is significant interindividual variation. Participants who swam or cycled regularly could count 30 minutes of continuous swimming or cycling as 3,000 steps toward their goal. The idea behind using the pedometers was to give participants something other than mileage and minutes as feedback for being more active.
The DPP’s “10,000 Steps” campaign lasted 4 to 6 weeks and included:
- a participant contract to reach 10,000 steps a day and a specified, individualized weight loss over a 4-to-6-week period
- a local DPP lifestyle walk
- a mailing to announce the walk to
- a group event to close the campaign, at which the participants were weighed and congratulated for their efforts
- entry into a local drawing at the end of the campaign for participants who recorded at least 50,000 steps per week
Many health care institutions and health plans have adopted the “10,000 Steps” program. Some offer a parallel Internet follow-up program for participants. Merely call up “10,000 Steps” on any search engine and you can pick and choose. There are many pedometers and activity counters to choose from; the Digi-Walker and Accusplit Eagle 120 are among the simplest and least expensive.
The large reduction (58 percent) in diabetes risk among the DPP lifestyle group was attributed primarily to moderate fat weight reduction (~10 pounds average over 3 years was actually lost), especially in the abdominal region. What is remarkable is that only 700 to 800 kcal per week of
exercise, coupled with moderate dietary changes, was the stimulus to induce such changes. This result becomes even more profound when contrasted with the 31 percent improvement in the group treated with metformin.
In an exercise program designed to reduce risk of diabetes (or cardiovascular disease), the most relevant stimulus is total energy expenditure (e.g., 700-1,000 kcal/
week) rather than exercise mode or intensity per se. Personal trainers can invoke the DPP outcomes and strategies to build partnerships with physicians and diabetes management programs and to help them plan and staff formal diabetes prevention programs for high-risk adults (e.g., those with metabolic syndrome). To succeed with these programs, fitness professionals will need to be proficient at instilling effective levels of motivational readiness in their clients for all forms of physical activity—in and outside of the fitness center.
Centers for Disease Control and Prevention. 1996. Physical Activity and Health: A Report of the Surgeon General. U.S. Dept of Health and Human Services.
DPP Research Group. 1999. Diabetes Care, 22, 623-34.
DPP Research Group. 2002a. Diabetes Care, 25, 2165-71.
DPP Research Group. 2002b. New England Journal of Medicine, 346, 393-403.
Helmrich, S.P., et al. 1991. New England Journal of Medicine, 325, 147-52.
Jeffery, R.W., et al. 1998. Journal of Consulting and Clinical Psychology, 66, 641-5.
Pate, R., et al. 1995. Journal of the American Medical Association, 273, 402.
Methods used to help participants achieve the DPP’s two major lifestyle goals included the following key features:
- individual case managers or “lifestyle coaches”
- frequent contact with participants
- a structured, state-of-the-art, 16-session core curriculum that taught behavioral self-management strategies for weight loss and physical activity
- supervised physical activity sessions
- a more flexible maintenance intervention, combining group and individual approaches, motivational campaigns and “restarts”
- individualization through a “toolbox” of adherence strategies
- tailoring of materials and strategies to address ethnic diversity
- an extensive network of training, feedback and clinical support