Challenging Dogma - Fall 2007

...Using the social and behavioral sciences to improve the practice of public health.

Tuesday, December 11, 2007

The 2005 Dietary Guidelines: an Approach to Help Prevent Growing Waist Lines that has the U.S. Searching for the Next Pant Size Up –Corinne Dobbas

The U.S. has a significant weight problem. The number of overweight and obese individuals is growing (1) Overweight and obesity are labels that deem someone as beyond the normal weight range for what is considered healthy, yet there is a substantial difference between the two (2). Comprehension of this difference enables one to fully understand the severity of our nation’s weight problem. For adults, body mass index (BMI) classifies their current weight by taking their height into account. An adult with a BMI between 25 and 29.9 is considered overweight, and an adult with a BMI of 30 or greater is considered obese (2). For children (aged 2-19), a BMI-for-age is used, which is age and sex specific. Their BMI-for-age is plotted on a BMI-for-age growth chart to obtain a percentile ranking. If the child’s percentile ranking is equal to or greater than the 95th percentile, then he or she is considered overweight. The term obese is not used in classifying a child’s weight (3).

Currently, 66% of the U.S. population aged 20-74 years is overweight and approximately 33% is obese. The prevalence of overweight adults, aged 20-74 years increased from 47% in1980 to 66% in 2004. Moreover, the incidence of obese individuals in the U.S. increased from 15% in 1980 to 32.9% in 2004 (1). Children are not excluded from the U.S. overweight crisis. Data from 1980 -2004 shows that the amount of overweight children has dramatically increased: for children aged 2-5 years the prevalence of overweight increased from 5.0% to 13.9%; for those aged 6-11 years, the prevalence increased from 6.5% to 18.8%; and for those aged 12-19 years, prevalence increased from 5.0% to 17.4% (4). Furthermore, in 2006 only four states had a prevalence of obesity less than 20%, twenty-two states had a prevalence equal to or greater than 25%, and two states had a prevalence of obesity equal to or greater than 30% (5). Overweight and obesity increases one’s risk of many diseases and health conditions, such as hypertension, dyslipidemia, type 2 diabetes, coronary artery disease, stroke, gallbladder disease, and some cancers (4).

The U.S. overweight and obesity problem is worsened by lack of physical activity. Regular physical activity reduces the risk of dying from heart disease and developing diabetes, high blood pressure, and colon cancer. In addition, exercise helps reduce blood pressure in people who have hypertension and helps control weight, develop lean muscle, and reduce body fat (6). Currently, more than 60% of adults do not achieve the recommended amount of regular physical activity (30 minutes on most days of the week) to reduce the risk of chronic disease. In actuality, 25% of adults are not physically active at all. Furthermore, about 50% of young people aged 12-20 years are not vigorously active, defined as 20 minutes of running, basketball, or bicycling 3 times per week on a regular basis (6).

The Dietary Guidelines for Americans provide science-based advice to promote health and to reduce risk for chronic diseases through diet and physical activity. The Dietary Guidelines are targeted to the general public over two years of age who are living in the U.S. These guidelines provide key physical activity recommendations to help deter the U.S. weight problem. The recommendations of the 2005 Dietary Guidelines are to engage in at least 30 minutes of physical activity to reduce risk of chronic disease and participate in approximately 60 minutes of activity to help manage weight and prevent gradual, unhealthy weight gain in adulthood. The Guidelines also state that 60-90 minutes of physical activity is needed to sustain weight loss in adulthood. Lastly, 60 minutes of physical activity on most days of the week is recommended for children and adolescents (7). Providing the American public with the physical activity recommendations in the 2005 Dietary Guidelines is a flawed public health approach aimed at facilitating a reduction in and prevention of the U.S. overweight and obesity problem. The recommendations fail to encompass social cognitive theory regarding the geographic availability of places to exercise and one’s concept of self-efficacy and assume that intentions are directly linked to behavior.

Overview of Social Cognitive Theory

Bandura and colleagues developed the social cognitive theory in the 1970s. The foundation of this theory is that the expectation of personal mastery and success determines whether or not an individual will engage in a particular behavior (8). Outcome expectancy and self-efficacy are the main influences of behavior in this theory. Outcome expectancy is the conviction that certain behaviors will lead to certain outcomes. Self-efficacy is the conviction that one can successfully execute the behavior that is required to achieve desired outcomes (8). Social cognitive theory supports that one’s belief in their own ability to perform a behavior (self-efficacy) is an important link between knowing what one should do and actually doing it.

Various studies examined the concept of self-efficacy in regards to health behavior. These studies support that it is one’s perceived capabilities rather than the known benefits of a health behavior that influences behavior. When health behavior is difficult to change –even if the behavior change results in benefits that are desirable –self- efficacy is a significant factor in helping make the change (8). This is emphasized by the many studies and review articles which suggest that self-efficacy is a key predictor of whether individuals adopt and maintain physical activity (9). One study found that people who believed that they could participate in physical activity exercised more. Furthermore, those who exercised generally had higher amounts of self-efficacy to participate in healthy behaviors than those who did not. Thus, one’s physical activity level is significantly correlated with self-efficacy (9). Further research shows that those with higher levels of self-efficacy are more likely to engage in and maintain their exercise behaviors (10). Hence, self-efficacy is a consistent and powerful predictor in behavior.

The Physical Activity Recommendations Fail to Consider Geographic Availability of Places to Exercise

Simply providing the public with the Dietary Guidelines’ key physical activity recommendations is not enough. They will not increase Americans’ level of physical activity because they do not account for the geographic availability of places to exercise, such as gyms, parks, sidewalks, fields, and bicycle paths. The differences in peoples’ physical environments have a substantial impact upon their amount of exercise (11-12). The guidelines fail to provide the public with tools to incorporate exercise into their life regardless of their physical environment. Consequently, if a person lives in an environment that is not conducive to exercise, they will assume that they are unable to meet their recommended amount of physical activity. A person who believes that they can not carry out a certain behavior has low self-efficacy. Individuals with low self-efficacy are likely to abstain from physical activity (9-10). Social cognitive theory shows that individuals who do not believe that they can accomplish a particular behavior will not act upon changing that behavior, regardless of intentions (8).

Studies show that access to recreational centers, neighborhood safety, and enjoyable scenery are related to physical activity (11). Thus, one’s physical environment has the capacity to impede or facilitate exercise. For example, the presence of bicycle paths or basketball courts may make it easier for a person to be physically active, whereas, the absence of such facilities or high crime rates may pose as a barrier to physical activity (11). One study found that residents of high-walkability neighborhoods exercised more and had a lower overweight prevalence than residents of low-walkability neighborhoods. High- walkability neighborhoods were identified as having high residential density, land use mix, street aesthetics, and safety. Low-walkability neighborhoods were characterized by low-density, automobile-dependent, segregated-use patterns of land and transport. Residents of high-walkability neighborhoods had 70 more minutes of physical activity per week than low-walkability residents. Additionally, only 35% of people in high-walkability neighborhoods were overweight compared to 60% of those in low-walkability neighborhoods (12). Another study showed that the density of exercise facilities, such as gyms and indoor pools around one’s house, is associated with exercise habits independent of demographic variables such as age, education, and income (11).

The geographic location of a person has a large impact upon their exercise routines. Moreover, individuals who live in an area of low-walkability or without a gym nearby may assume that daily physical activity is not a possibility for them regardless of the fact that they know it is good for them. Their self-efficacy will be low, which will cause them to not partake in physical activity –let alone adhere to the time consuming high-standards that the Dietary Guidelines recommend. As previously stated, studies regarding social cognitive theory show that self-efficacy is a key determinant in changing or maintaining a health behavior (8-10). The recommendations do not account for this concept in regards to one’s geographic location, failing to help aid the U.S. lack of physical activity and consequently, have done little to curb the nation’s weight problem.

The Physical Activity Recommendations Fail to Consider Self-Efficacy

The physical activity recommendations in the Dietary Guidelines are unsuccessful in preventing and reducing the number of overweight and obese individuals because they do not incorporate self-efficacy. The recommendations for exercise are substantial: 30 minutes per day to reduce risk of chronic disease, 60 minutes per day to prevent unhealthy weight gain, and 60-90 minutes per day to sustain weight loss (7). These recommendations are above Americans’ usual daily activities, which makes it difficult for busy people to believe that they can allot this amount of time to exercise. Currently, 60% of adults do not achieve the goal of exercising 30 minutes per day five days of the week and 25% of adults do not participate in any sort of physical activity. Furthermore, 50% of young people fail to exercise 20 minutes three times a week (6). Clearly, if a person is unable to meet the bare minimum requirement of 30 minutes of physical activity most days of the week, then they will neither seek to achieve 60 minutes of exercise per day to prevent unhealthy weight gain, nor 60-90 minutes of physical activity per day to sustain weight loss. Therefore, the guidelines are a public health failure in their efforts to reduce and prevent the amount of overweight and obese individuals. Americans do not have the self-efficacy to exercise 30 minutes a day and some do not have the self-efficacy to exercise at all (6). By ignoring this fundamental fact, the Guidelines’ physical activity recommendations do not offer any worthwhile advice to help lose weight. Their efforts were intended to help prevent and reduce the U.S. weight problem; however, they set their standards too high (6-7). Americans do not have the self-efficacy needed to carry out these recommendations. And, self-efficacy has been shown to play a substantial role in achieving and maintaining physical activity recommendations (8-10).

The Physical Activity Recommendations Fail Due to Apparent Use of the Health Belief Model

The Health Belief Model (HBM) is a behavioral model based on rational decision making. The HBM assumes that human behavior is determined by an objective, logical thought process. The basic components of the HBM are the individual’s value of a particular outcome and their belief that a certain action will result in that outcome. Thus, for individuals to change their behavior to avoid a disease they would need to believe that the outcome of their altered behavior would have a more beneficial effect than not changing their behavior. Ultimately, the HBM assumes that intentions link directly to behavior (8).

For example, according to the HBM, a person who knows the benefits of physical activity, such as helping maintain a healthy body weight and reducing risk of heart disease, and who is aware that exercise will reduce their susceptibility of various health problems will exercise. This person would believe that their maintained weight and reduced risk of heart disease is more beneficial than the problems associated with not exercising –hypertension and cardiovascular disease. However, that is often not the case due to busy schedules, lack of motivation, bad weather, and a lack of nearby facilities (11-13).Even though a person intends to exercise because they know the benefits and the various health problems associated with not engaging in physical activity does not mean that the individual will in fact exercise.

The Guidelines seem to be based on the HBM, which does not account for the factors preventing people from exercising. Several studies reported that a person’s perceived barriers to exercise are an important determinant of how active he or she becomes (13-15). Some perceived barriers include depression, fatigue, high workload, bad weather, and lack of facilities, transportation, or competent instruction. A person who has many perceived barriers regarding exercising is less likely to participate in physical activity (13). One study showed that over 50% of people reported that they would choose exercise over alternative leisure time activities, yet these people did not engage in physical activity due to a variety of reasons. Reasons included cost and time constraints, the difficulty of exercising, importance of other obligations, lack of fun, uncertainty of how to begin, and embarrassment due to weight, age, or level of fitness (14). Additional studies show that if a health professional discusses ways for a person to overcome their barriers to exercise, then they are more likely to adopt and maintain their activity program (15).

The Guidelines’ seeming use of the HBM does not cause a person to start or continue exercising. As previously discussed, self-efficacy is not emphasized and ways to overcome a person’s perceived barriers to exercise are not indicated. The HBM has failed to receive any clear support in the literature on adult physical activity correlates (16). The American public needs guidance on how to overcome the numerous obstacles that prevent them from exercising. The exercise Guidelines given to the public do not provide such guidance. The guidelines’ writers simply assume that the publics’ intentions to be healthy will cause them to exercise. Hence, the recommendations have not helped prevent or reduce the U.S. weight problem because this elemental issue has not been addressed.

Implications for Future Public Health Programs

The Dietary Guidelines’ physical activity recommendations are based on scientific evidence, thus, these exercise guidelines are well founded. However, the Guidelines have failed to implement these recommendations within the community at large. People need direction on how to incorporate exercise into their lifestyle regardless of schedules, prior commitments, not having a gym membership, and living in a low-walkability neighborhood. People must believe that some activity is better than none. In fact, this could get sedentary individuals to exercise, build self-efficacy, and slowly incorporate physical activity into their lifestyles. Currently, the stakes are set to high, causing individuals to not partake in any physical activity due to lack of self-efficacy and multiple perceived barriers (10-15).

A public health campaign that uses marketing theory would be of great use to help motivate people to exercise. Marketing theory is a means of promoting a behavior change by treating the behavior as a desirable product. Thus, people would voluntarily adopt the new health behavior because they believe that the behavior is beneficial and offers fulfillment of their needs (17). In this regard, marketing theory would be used to first determine the desires of the American public and then design the campaign to meet these desires, “selling” physical activity. After “selling” exercise, it would then be necessary to address the subsequent issues of a person’s geographic location, self-efficacy, and overcoming exercise barriers (10-14, 17).

Once a public health campaign addressed the public at large, efforts to become more specific to the individual would be a key aspect in physical activity promotion. For example, free sessions with healthcare professionals within community centers could be offered. These appointments would allow people to find ways of incorporating daily activity into their lives, regardless of their geographic location. Ways to decrease perceived barriers could also be discussed. A person’s self-efficacy should increase by addressing the key components of geographic location and perceived barriers, causing them to exercise more. Additionally, healthcare providers could develop a workout plan specific to individuals. The plan would include the type of exercise, when and where they would workout, and for how long (9-15).

Communities and cities could also help individuals increase physical activity. This would be accomplished by making physical environments more conducive to exercise. Attractive trails for walking, biking, or running could be made or outdoor basketball courts could be built. Exercise and weight loss groups could also be adopted or more emphasized within communities. Lastly, employers could pair up with local gyms (if accessible) to allow for discounts for their employees, and health professionals could go into schools to speak with kids about ways to improve their activity levels (6, 10-14). Ultimately, The Dietary Guidelines have failed to address these issues and provide the American public with the necessary “tools” to incorporate physical activity into their lifestyle, failing in their efforts to help curb the U.S. weight problem.


The current data indicate that the U.S. weight problem is deteriorating rather than improving (4). The physical activity recommendations set forth by The 2005 Dietary Guidelines for Americans have not impacted the prevention or reduction of overweight or obese individuals. This is due to their ignorance of the need to address a person’s self-efficacy, geographic location, and exercise barriers. The apparent use of the HBM illustrates a key factor in their fruitless recommendations. The Dietary Guidelines provide scientific data in regards to physical activity but fail to address fundamental principles of human behavior that are necessary to yield a successful approach to public health. The exercise recommendations fail to help aid the U.S. overweight and obesity crisis. A new approach is needed immediately.


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