CHAPTER 3: Proof That Lifestyle Matters: The Diabetes Prevention Program

Excerpted from Beating Diabetes: The First Complete Program Clinically Proven to Dramatically Improve Your Glucose Tolerance

By David M. Nathan, M.D. and Linda M. Delahanty, M.S., R.D.

Reprinted by permission of the McGraw-Hill Companies; © Copyright 2005 by President and Fellows of Harvard College. All Rights Reserved.

For more information or to purchase this book, follow this link:
http://www.health.harvard.edu/books/Beating_Diabetes.htm

Don't you already know a lot about diets and exercise programs? Unless you've been living in a cave, cut off from all communication, you probably do. You have, like the rest of us, probably been flooded with advertisements and party talk about how to "eat healthy" and lose weight. Weight loss programs abound. In addi­tion to the potential health benefits of weight loss, its cosmetic appeal has spawned a multibillion-dollar weight loss industry that includes diet books and programs, food supplements, over-the-counter and prescription medications, stomach-restriction surgery, and plastic surgery. It also includes exercise books, tapes, videos, television shows, and equipment; Jazzercise; step and bicycle aer­obics; yoga exercise; combat yoga; sweat yoga; and Tae Bo. Indeed, health clubs have grown in parallel with the size of our waists.

The enthusiasm for so many approaches to weight loss must be because none of the programs is overwhelmingly effective. The recurring failure of the programs has led an increasingly obese population to search, in desperation, for any answer. And although plenty of "answers" are out there, virtually none of them has been put to the scientific test. We don't have an answer to a very simple question: Do the programs work? This question must be answered not just in the short term, when almost any program can work, but in the long term; we don't know whether the programs are effective over a long enough period of time to improve health. In this and subsequent chapters, we summarize what is known scientifically about what works—and what doesn't—for losing weight and improving health. Of the many health goals that weight loss and increased physical activity might achieve, preventing diabetes may be the most important.

As we described in Chapters 1 and 2, the origin of the diabetes epidemic can be clearly traced back to changes in lifestyle. In the absence of our current maladaptive lifestyle, diabetes and its complications would probably be relatively rare. If that is so, would a program to reverse our current maladaptive lifestyle prevent diabetes? If we could restore at least some elements of the "farmer's life," could we reduce the risk of developing diabetes? To know the answers requires a scientific study.

In the past few years, several such studies have proved that you can protect yourself against getting diabetes by changing your lifestyle and that most people can make the changes successfully. As members of the Diabetes Prevention Program Research Group, we helped to organize the largest of those studies. To explain what these studies have shown, we first need to explain the kinds of scientific studies that have led to the program that we describe in this book.

Observational Studies: The First Scientific Studies of Nutrition and Exercise

Until the twentieth century, anyone recommending a particular diet or exercise program did so without any reliable scientific evi­dence to support it. They might have observed the results of dif­ferent diet or exercise routines and then drawn conclusions. Sometimes their powers of observation were good, and—when proper scientific studies were eventually performed—they turned out to be right. Other times they were wrong but had no way of knowing it. Without a scientific method of comparing one approach versus another, enthusiasts could conclude pretty much anything they wanted. The English philosopher Roger Bacon noted, "For what a man had rather were true, he more readily believes." Barbers, shamans, gurus, and doctors could become true believers in their ineffective nostrums.

The first scientific studies of nutrition and exercise began in the middle of the twentieth century. The initial studies were called observational studies. In an observational study, a group of people is examined at least once (a cross-sectional study) or, more typically, is followed over time (a longitudinal study). Informa­tion—or data—regarding nutrition and exercise is collected with standardized methods and as objectively as possible. In addition, these observational studies collect information about any diseases or conditions that develop over time.

In such observational studies, the investigator can ask whether people who eat certain foods (for example, high-fat and high-calorie diets) or who exercise to a certain degree (for example, for an hour or less a week) have a greater tendency to develop disease than the members of the population who behave differ­ently (for example, eat low-fat, low-calorie diets). If there are cer­tain diet or exercise patterns that are associated with a greater risk of certain diseases, then it is possible that those diet and exer­cise patterns increase the risk of those diseases—possible, but not proved.

Why does an observational study not prove a direct connec­tion between a particular diet or level of activity and disease? The reason is that an association cannot prove causality. For example, if an observational study were to show that people who eat high-fat and high-calorie diets are more likely to develop diabetes, it might not have been the diet that caused the diabetes. There might have been something else about the people who chose such a diet—maybe they thought they were at high risk for diabetes and thought that a high-fat diet would be good for them. Or perhaps people who eat a high-fat and high-calorie diet follow some other behavior, such as smoking or taking a particular medicine, that actually caused the diabetes. Observational studies have proved immensely valuable in pointing out factors (such as par­ticular diet and exercise patterns) that are associated with increased risk of disease. But they cannot prove that those patterns cause disease.

To prove causation requires a different type of study from a purely observational one. It requires an experiment in which the investigator manipulates the factor that he or she thinks causes a specific outcome. The factor might be a low-calorie diet or a medicine or both. These types of experiments are called randomized controlled clinical trials. Observational studies and randomized controlled clinical trials are discussed in more detail in Appendix A.

Why Randomized Controlled Clinical Trials Are So Important

A randomized controlled clinical trial is a true experiment. To perform a controlled clinical trial of a diet and exercise program, the investigator first needs to enlist the participation of research volunteers. The choice of volunteers to be recruited will depend on the goals of the study. For example, in the Diabetes Preven­tion Program we and our colleagues chose individuals at high risk to develop diabetes.

What distinguishes a randomized controlled clinical trial from an observational study is that the people recruited to participate in the study are assigned at random either to be in the experi­mental intervention group or to be in the group that receives either standard therapy or sometimes no therapy (the "control group"). All of the study subjects are then followed, sometimes for years, to see whether there is a difference in the development of diseases between the two—or more—groups. The random—by chance—assignment of the groups means that the two groups most likely will be similar at baseline, before the interventions are applied. Therefore, if a particular disease develops less often in the subjects assigned to the experimental intervention program, compared to those assigned to the control program, then researchers can conclude that the experimental intervention almost certainly caused the reduced risk of disease.

The Diabetes Prevention Program

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 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 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.

In summary, the DPP study showed that lifestyle changes had a greater power to prevent diabetes than the medicine we tested. The lifestyle program that the people in our study were asked to adopt proved feasible for them. Lifestyle changes should be suitable for you, too. We hope that this book will provide not only the rationale but scientifically proven guidance as to how you can change your lifestyle to a healthier one that can prevent diabetes and its complications.

CHAPTER 6: How to Get Ready to Change Your Lifestyle

Are you really ready to lose weight? If asked, most people who are overweight will say, "I really want to lose weight." Most overweight people can also list several reasons why they want to lose weight. But the more difficult questions to answer are: Are you ready to do what it takes to lose weight? Are you really ready and willing to change your eating and exercise habits? Examining your readiness to change and your "motivators" and "demotivators" for losing weight are critical first steps in the process of last­ing lifestyle change.

What It Means to "Be Ready"

Scientists who study behavior change have identified five stages that people go through when trying to change their habits: precontem­plation, contemplation, preparation, action, and maintenance.

People in the precontemplation stage are either not interested in or not thinking about making changes in lifestyle in the next six months. They may not see their weight as a threat to their health, or they may have too many other competing priorities and may just not be ready to focus on lifestyle changes.

If you have moved on to the contemplation stage, then you are thinking about making lifestyle changes within the next six months. You are likely weighing the advantages and disadvan­tages of changing your exercise and eating habits. People in the contemplation stage are usually looking for motivation and typ­ically say, "I know I should want to lose weight," or, "I need a program to motivate me." They are usually waiting for the magic moment to start, or hoping for a magic pill—the newest fad diet or gimmick that promises quick results with little effort. When they examine the way they talk about losing weight or making lifestyle changes, they find themselves saying, "I know I should, but . . ." or, "It takes too much effort."

The next stage is preparation. People in the preparation stage are planning to make lifestyle changes within the next month. They may have started to make small changes in exercise and eat­ing habits and are interested in doing more. They may be ready to sign up for an exercise class or keep a record of food intake. They usually express an inner motivation to make changes and do not look for (or rely on) external motivators, such as a program or someone else to inspire them.

The action stage is where desire and planning become mani­fest as distinctive changes in behavior. If you are in the action stage, you have made changes in your exercise and eating behav­iors within the past six months and are trying to become more consistent with your new lifestyle habits. People in the action stage will say, "It's getting easier for me to manage my food choices and fit exercise into my routine." Or, "I'm making good progress with weight loss, but sometimes I get off track."

Being in the maintenance stage means that you have main­tained your new exercise and eating habits for longer than six months. These lifestyle changes have become part of your daily routine. While you actively try to avoid slipping back into old habits, you're also becoming increasingly confident about your ability to maintain your new ways. You might say things such as, "I just do it now." Or, "My new lifestyle is just a part of me."

So where are you right now? What is your stage of change? How can you become someone whose lifestyle remains in the maintenance stage for weight loss, eating habits, and physical activity? Table 6.1 describes these stages and the statements char­acteristic of the thinking that takes place during each stage. See where you are at this point. The next section will help you determine which stage you are in.

How You Can Gauge Readiness to Change

First of all, it is important for you to know that people do not simply progress through the stages of change in order; they can enter or exit the stages at any point, and they can recycle through the stages by relapsing and repeating stages. For example, life stresses can sometimes cause you to slip and lose focus on your exercise/activity and eating habits, and you may move from the action stage for weight loss, eating habits, and exercise back to the contemplation stage for a period of time. Vacations, social gatherings, or retirement can also cause you to get off track because they disrupt your usual routine. It is also possible to be at one stage of change for reducing calorie intake and at a dif­ferent stage of change for increasing activity.

To understand how you 're moving through the stages of change, it's helpful to examine your motivations. There are sev­eral ways to do this, and it is absolutely worth the effort to carefully examine the various aspects of what motivates you.

First ask yourself the following questions that have been adapted from a book called Health Behavior Change: A Guide for Practitioners, by S. Rollnick, P. Matson, and C. Butler, and pub­lished by Churchill Livingstone in 1999:

On a scale of 0 to 10, with 0 being "not important at all" and 10 being "the highest importance," how important is it for you right now to lose weight?

0 1 2 3 4 5 6 7 8 9 10

If you decided to lose weight right now, on a scale of 0 to 10, with 0 being "not confident at all" and 10 being "very confi­dent," how confident are you that you could lose weight?

0 1 2 3 4 5 6 7 8 9 10

To lose weight, it is necessary to reduce food portions and calorie intake and to increase your activity level. So it is also necessary to rate the importance and your confidence for changing these behaviors. People often have different importance and con­fidence ratings when rating changing eating and exercise habits. So be honest with yourself about the next questions:

On an importance scale of 0 to 10 (as in the previous questions), how important is it for you right now to reduce your food por­tions and calorie intake?

0 1 2 3 4 5 6 7 8 9 10

If you decided to lose weight right now, on a confidence scale of 0 to 10 (as in the previous questions), how confident are you that you could reduce your food portions and calorie intake?

0 1 2 3 4 5 6 7 8 9 10

On an importance scale of 0 to 10, how important is it for you right now to increase your activity level?

0 1 2 3 4 5 6 7 8 9 10

If you decided to increase your activity level right now, on a con­fidence scale of 0 to 10, how confident are you that you could increase your activity level?

0 1 2 3 4 5 6 7 8 9 10

Now let's see what your answers mean.

Importance Ratings

Importance ratings of 7 or higher imply that it is pretty impor­tant for you to lose weight, reduce calories, and exercise more. If you gave importance ratings of 5s or 6s, then you may be somewhat ambivalent about these lifestyle changes. If your importance ratings are 4s or lower, making these changes is of fairly low to very low importance to you right now. You are likely in the precontemplation or contemplation stage of change.

Confidence Ratings

Confidence ratings of 7s or higher suggest that you 're pretty con­fident to very confident that you can lose weight, change your eating habits, or exercise more. If your confidence ratings were 5s or 6s, you may be uncertain about your ability to lose weight and make the necessary changes in your eating and exercise habits. If your ratings are 4s or lower, you don't have a lot of con­fidence that you can lose weight, cut calories, and exercise more.

What to Tackle First

If your importance ratings are lower than 3s, you'll want to focus on importance first. If both importance and confidence ratings are the same, you'll still want to focus on importance first. However, if one rating is distinctly lower that the other, start with the lower rating first. If both your importance and confidence rat­ings are below 3s, then this may not be the ideal time for you to try to lose weight. On the other hand, if both importance and confidence are high, then you're probably ready to take steps toward long-term lifestyle changes. Let's look at some real-life examples.

Bob

Bob is forty-eight years old with a twin brother who has had dia­betes for three years. He has just found out that he has impaired glucose tolerance or prediabetes. His doctor has told Bob that he's very likely to develop type 2 diabetes within five years of his twin brother. When Bob joined the Diabetes Prevention Program (DPP) study, he was five feet ten inches tall and weighed two hundred pounds. His motivation score was 9 out of 10; however, his confidence score was only 5 out of 10.

Bob had never been on a weight loss program before, perhaps explaining his low sense of confidence. However, he was excited to learn that he had been assigned to the lifestyle intervention group. Bob's wife attended each of Bob's individual coaching ses­sions to learn how she could support his efforts. At first they found that keeping food records and learning about sources of fat and extra calories in their diet was time-consuming. They also found it difficult to adjust the traditional Italian recipes that the family enjoyed. With practice, feedback, and support Bob found out that he could change his eating and lose weight and that over time it got easier. Difficult changes started to become habit. As he saw progress and experienced success, he became increasingly confident that he could maintain his lifestyle changes over time and keep the weight off. Bob's weight loss goal for the study was to reach 186 pounds (a 7 percent weight loss), and after six months, he had lost 15.5 pounds and weighed 184.5 pounds. In addition, he kept this weight off for five years, and at the end of the DPP, his blood sugars had returned from impaired to normal.

Mary

Mary is a forty-seven-year-old woman with type 2 diabetes. She was five feet five inches tall and weighed 244 pounds (BMI 41) at the start of her program, and she was taking several diabetes medications, including metformin (Glucophage), glimepiride (Amaryl), and pioglitazone (Actos). Mary's motivation to change her eating and exercise habits to lose weight was a 10 out of 10. Her confidence level was 7. She participated in a group weight loss program with a goal of losing 10 percent of her body weight.

After six months, Mary lost thirty-two pounds (a 13 percent weight loss) and weighed 212 pounds. Her blood sugars improved dramatically, and she was able to stop taking the Amaryl. Although Mary wanted to get below 200 pounds, she found that her weight fluctuated between 210 and 215 pounds. When asked to rate her motivation for losing those extra pounds, she was somewhat surprised to hear herself say 2 out of 10. When asked how important it was to reduce her diabetes medications further, she rated her motivation to come off the Actos as 8 out of 10.

Together we decided that Mary would meet with her primary care physician to discuss her goals. She asked her doctor if she could try stopping the Actos because her blood sugars were so good. Mary agreed to continue regular blood sugar monitoring. She knew that to keep her blood sugars well controlled she would need to be especially careful with her food choices and that losing more weight would make it more likely that she could remain off the medication. Now, her motivation to lose weight was 8 out of 10, and she dropped to 199 pounds over the next eight weeks! She is still off the Actos and maintaining good blood sugar control.

How to Analyze Your Importance and Confidence Ratings

Let's look more closely at your situation. Your importance rating for losing weight was _____. Now, list all of the reasons why your rating was not one or two points lower.

________________________________________________

Next, list what it would take to increase your importance rat­ing by three points.

________________________________________________

Your importance rating for reducing calorie intake was ______. List all of the reasons why your rating was not one or two points lower.

________________________________________________

Next, list what it would take to increase your importance rat­ing by three points.

________________________________________________

Your importance rating for increasing your activity level was ______. List all of the reasons why your rating was not one or two points lower.

________________________________________________

Next, list what it would take to increase your importance rat­ing by three points.

________________________________________________

Are your importance ratings for losing weight, reducing calo­rie intake, and increasing activity level similar for all three lifestyle changes? If your ratings for weight loss are much higher than your ratings for reducing calories and increasing activity, then you need to think about whether you're truly ready to make lifestyle changes. Wanting to lose weight without recognizing the behavioral changes required to accomplish this goal is unrealis­tic, magical thinking. Losing weight may be very important to you, but is it important enough that you are willing to invest the time and effort to change your eating and exercise habits? For some people, eating and enjoying food, or using food to cope with unpleasant emotions, is more important than losing weight.

Now look at the reasons behind your ratings. This will help you understand how you view the perceived benefits (the "pros") of losing weight and the perceived barriers (the "cons") that get in your way. As you examine what would increase your ratings, you'll start to see what you'll need to do to start to reduce the barriers.

Let's take Kathy, a sixty-two-old woman with prediabetes, as an example. When she reviewed the pros and cons of losing weight, she first listed the ones that were important for her. Then she rated their importance on a scale of 0 to 10 with 10 being "the highest importance" (see Table 6.2). As you look at her responses, you'll see that the number of pros and cons for losing weight is certainly important, but so is their relative importance.

Although Kathy's list included a similar number of cons and pros, the relative importance of losing weight was greater than that of not losing weight. Her highest ratings were not for appearance but were related to better health and a better quality of life as she gets older. Kathy knows about the long-term complications of dia­betes and wants to do all she can to avoid them. Even though she loves to eat and often uses food to calm her "nerves," and even though she dislikes the inconvenience of keeping food records, the importance of her health and quality of life outweigh these factors.

Take some time to identify your own pros (motivators) and cons (demotivators) for losing weight and rate their importance to you using a scale of 0 to 10. Then total the value of your moti­vators and demotivators (see Table 6.3).

Which way does your scale tip? If the demotivators outweigh the motivators, ask yourself what you can do to tip the balance. How can you reduce the demotivators and increase the motivators?