Sedentary Americans: How Lack Of Emphasis On Exercise Education And Programs Exacerbates America’s Obesity Epidemic—Susanna Hamilton
Introduction
The obesity epidemic in the United Sates is well-documented, and the statistics are grim. In 1985, there were no states which reported an obesity rate of greater than 10-14%, and only 8 states fell into that 10-14% category (obesity being defined as a BMI of 30 or higher). In 1990, 34 states fell into the category of 10-14% obesity rate. By 2006, 4 states were in the 15-19% obesity rate category, 2 states were in the >30% category, and the remainder were quite evenly spread between 20 and 29% (1). A host of medical problems have been associated with obesity, ranging from the obvious to the surprising. These problems include heart disease and stroke, hypertension, diabetes, cancers, gallbladder disease, osteoarthritis, gout, and respiratory problems (2).
Nearly everyone has heard the rhetoric about the tried and true ways in which to combat obesity: healthy diet and exercise. However, either by accident or by design, diet receives the lion’s share of publicity about weight loss and weight maintenance. On two out of three websites for major diet programs, Atkins and South Beach, exercise is not mentioned at all in their plan (3,4). For a third diet program, Weight Watchers, exercise is mentioned, but only in passing and is not stressed (5). To be sure, a healthy diet is extremely important, but evidence from studies as well as implementation of the Social Cognitive Theory (6,7) show that increased exercise would help the problem of obesity just as much, if not more, than diet. However, there has been very little in the way of public awareness campaigns regarding exercise and its health benefits – both to help in the fight against obesity and in other areas of general health. Greater emphasis needs to be placed on the public’s awareness about the importance of exercise at every age.
The Focus On Diet Alone Is Bound To Fail—Slow Effects Lead To Lack Of Positive Reinforcement And Low Self-Efficacy
As stated above, when trying to combat obesity, the importance of diet is great. To this end, the USDA has for years relied on its promotion of the “food pyramid,” which explicitly shows how many servings of each types of foods are recommended every day to maintain a healthy diet. Categories of food groups consist of grains, vegetables, fruits, milk, and meats and beans (8). Promotion of and education about the food pyramid, while valuable, relies on the Theory of Reasoned Action. This theory aims to predict people’s behaviors (like new diets) by using their attitudes towards behaviors, the subjective norms towards behaviors, and his or her behavioral intention to carry out behaviors (9). It is based on the assumptions that a change in beliefs (such as a new-found belief that a healthy diet will help you lose weight) will lead to a change in behavior (such as an adoption of the food pyramid in making dietary decisions). Furthermore, it assumes that actions necessarily follow intentions (9). While this model certainly has useful aspects, it is fundamentally flawed in its use when it comes to the adoption of a healthy diet. Personal experience for many people, as well as common sense, says that most overweight and obese people know and believe that a healthy diet will lead to weight loss. But the acquisition of that belief does not necessarily lead to a change in eating behavior. (10). Even if an obese person intends adopt a new behavior and start following a healthy diet, the growing awareness of a healthy diet coinciding with American’s growing waistlines proves that actions in this case often do not follow intentions. A major reason for this is the time it takes for a healthy diet to take effect. Unless people are literally starving themselves, weight loss through a healthy diet alone is a slow and gradual process. It requires constant adherence, and nearly an all-day-every-day perseverance, which few people possess (10,11,12). Due to this fact, a healthy diet alone, while noble, promotes very little self-efficacy and positive reinforcement. Either people do not attempt healthy diets, because they know they cannot stick to them, or they quickly revert to their old diets. It takes a long time to see results (a reduction in Calories of 500-1000 per day will result in a drop of 1-2 pounds per week), and in the interim, grand intentions often stay intentions rather than leading to behaviors (13). Furthermore, once people fall off the wagon (a piece of birthday cake at a colleague’s party), self-efficacy lowers even further, leading to a pattern of unhealthy eating behavior.
For those people for whom the Theory of Reasoned Action initially does take hold and who change their diets to be healthier, countless studies have shown that the vast majority of people who lose weight on a lower-calorie, healthier diet eventually re-gain most or all of the weight they lost (11). For example, in a study conducted by the American Journal of Clinical Nutrition, obese men were placed on a very low calorie diet for 10 weeks, and after those 10 weeks were followed up to monitor weight gain. After being taken off the strict diet, many of the men re-gained the weight which they had lost. However, a second subset of men in the cohort were placed on the same low-calorie diet along with exercise. The two groups of men lost about the same amount of weight during the initial 10 week study phase, but after the diet phase, those who were put on the exercise program were less likely to re-gain the weight which they had lost (12). Indeed, a fact sheet from the American Medical Association (11) states that for maintaining weight loss, “weight regain is common. Combining a very low calorie diet with…physical activity…may help increase weight loss and prevent weight regain” (11).
Lack Of Focus On Exercise Fails To Recognize Its Immediate Positive Physical And Mental Effects Which Lead To High Self-Efficacy And Positive Reinforcement
The hallmark of the Social Cognitive Theory, a model for predicting behavior based on the interplay between people’s environments, behaviors and personal factors (6), is the concept of self-efficacy: people’s own senses of their abilities to adopt a new behavior. High self efficacy means that people believe a particular goal is attainable, whereas low self efficacy means that people know or believe that achievement of a goal is unlikely (7). As stated above, adoption of a new healthy diet in order to achieve weight-loss tends to little positive reinforcement. For one thing, an obese person who has just finished a low-calorie, healthy meal is unlikely to feel anything except hunger (11). Secondly, as stated before, the health and weight effects of a healthy diet are gradual, and as such, are unlikely to foster positive reinforcement. Exercise, on the other hand, has healthy diet beaten on both of these fronts (12,14).
First of all, exercise causes your body to release endorphins: hormones which give a person a natural high and general feeling of well-being (14). Personal experience shows that upon completion of exercise, whether that be a light workout or a 15-mile run, people immediately have a feeling of accomplishment and that feeling serves as positive re-enforcement for the rest of the day in terms of a healthy lifestyle. People feel physiological positive and immediate effects upon completion of exercise, which increase self-efficacy in a way that healthy eating cannot.
Secondly, exercise has immediate health effects which are indirectly related to weight loss. Studies have shown that exercise helps ease anxiety and depression (15,16). It stands to reason, therefore, that this reduction in anxiety and depression symptoms will lead to higher self-efficacy when it comes to continuing an exercise program. These positive effects feed off of each other: exercise releases endorphins and reduces depression and anxiety, which leads to higher self-efficacy in an exercise program, which reinforces the exercise program.
Lack Of Physical Education Classes In School Sets A Bad Pattern For Physical Activity Later In Life
The CDC recommends at least 30 minutes of moderate physical activity at least 5 days per week or at least 20 minutes of vigorous activity at least 3 days per week. However, the CDC reports that in 2005, there were only 7 states in which greater than 55% of the population met the recommended amount of physical activity. In four states, less than 40% of the population met the recommendations. In most states, between 40 and 55% met the recommendations (17). Furthermore, this pattern of physical inactivity begins at an early age. The CDC reports that in 2003, 52.8% of females and 58.5% of males in high school were enrolled in a physical education class. Only 34.9% of females and 43.6% of males were physically active during PE class during that same year (18).
Not surprisingly, this pattern of inactivity which begins at an early age persists later in life. A report on aging from the World Health Organization states that people who exercise early in life are more likely to exercise as adults (19). Conversely, and American Heart Association fact sheet reports that “inactive children are more likely to become inactive adults” (20).
These data are troubling, especially when examined using the framework of the Social Cognitive Theory, which includes life experience as one of its factors. The Social Cognitive Theory states that a people’s experiences in a behavior, whether that experience be successful or unsuccessful, has direct impact on their self-efficacy toward a behavior. Previous successful experience in a behavior will positively impact self-efficacy, whereas unsuccessful experience lowers it (7). This theory explains why many people may be reluctant to begin an exercise program, or have low self-efficacy in doing so. People who have led sedentary lifestyles all throughout childhood will not have positive exercise experiences to draw upon in order to increase self-efficacy, whereas people who participated in sports or physical education classes in their youth will be more likely to be comfortable using physical activity as a tool with which to combat obesity.
Indeed, a study of former college rowers conducted in the Journal of American Board of Family Practice shows that, for both men and women, incidences of obesity were significantly lower later in life than for the population at large. This indicates that people who participated in athletics in college had successful experiences with exercise, and as a result, have high self-efficacy when it comes to adopting an exercise program later in life (21).
Conclusion
Nobody contests the fact that maintaining a healthy diet is important, especially when it comes to a reduction in saturated fats, trans fats and cholesterol, in combating the obesity problem in our country. However, it is unrealistic and irresponsible to emphasize diet alone because people are bound to fall off the wagon. The focus on a healthy diet overlooks key flaws in the Reasoned Action Model, has low self-efficacy and as a result, a low success rate. One need only to look at trends in the obesity rates in America to support this notion. An exercise program is just as important, if not more important, than diet in maintaining a healthy weight. Because its immediate effects promote self-efficacy and a healthy cycle of behavior, it’s vital in the battle to combat obesity, yet too often it is overlooked and not stressed enough. The most important step we as a society can take to reverse this inactivity trend in the United States is to increase physical activity at all ages, especially in youths, both in school and outside of school. The Social Cognitive Model postulates that positive experience in a behavior leads to high self-efficacy later in life, and studies such as that of the college rowers show this to be the case. Kids need to get moving at an early age. Get them comfortable with physical activity. That way, when they gain unwanted weight later in life, they are in a position to know they have the power and ability to do something about it, and not just sink into a dangerous and possibly deadly food cycle.
References
1. Department of Health and Human Services: Centers for Disease Control and Prevention. U.S. Obesity Trends: 1985--2006. www.cdc.gov/nccdphp/dnpa/obesity/trend/maps/index.htm. Accessed 30 November, 2007.
2. WebMD. Weight Loss: Health Risks Associated With Obesity. http: www.webmd.com/cholesterol-management/obesity-health-risks. Cleveland Clinic. Accessed 30 November, 2007.
3. Atkins Phases. Atkins Advantage: The New Look of Nutrition. http://www.atkins.com/articles/atkins-phases. Accessed 30 November, 2007.
4. The South Beach Diet Online: About the Diet. http://southbeachdiet.com/public/about-the-south-beach-diet/about-the-south-beach-diet.asp?GID=201. Accessed 30 November, 2007.
5. Weight Watchers. The Flex & Core Plan. http: www.weightwatchers.com/plan/eat/plans.aspx. Accessed 30 November, 2007.
6. Bandura, A. Social learning theory. Englewood Cliffs, NJ: Prentice Hall, 1977.
7. Bandura, A. Social cognitive theory: An agentic perspective. Annual Review of Psychology. 2001; 52, 1-26.
8. Department of Agriculture. My Pyramid Plan. www.mypyramid.gov. Accessed 30 November, 2007.
9. Fishbein, M., & Ajzen, I. Belief, Attitude, Intention, and Behavior: An Introduction to Theory and Research. Reading, MA: Addison-Wesley, 1975.
10. Cachelin, FM et al. Beliefs About Weight Gain And Attitudes Toward Relapse In A Sample Of Women And Men With Obesity. Obesity Research 1998; 6(3): 231-7.
11. Department of Health and Human Services: National Institutes of Health: Weight-Control Information Network. Very Low Calorie Diets.. http://win.niddk.nih.gov/publications/low_calorie.htm. Accessed 30 November, 2007.
12. van Aggel-Leijssen, Dorien P.C., et al. Short-term effects of weight loss with or without low-intensity exercise training on fat metabolism in obese men. Am J Clin Nutr;73:523-31.
13. Department of Health and Human Services: National Heart Lung and Blood Institute: The Practical Guide: Identification,Evaluation, and Treatment of Overweight and Obesity in Adults. http://www.nhlbi.nih.gov/guidelines/obesity/prctgd_c.pdf. Accessed 30 November 2007
14. Michaels, Jillian. Exercise, Endorphins, and Your Health. Diet & Body. http://dietandbody.com/exercise/2007/08/exercise-endorphins-and-you.htm. Accessed 30 November 2007.
15. Trivedi, MH, et al. Exercise as an Augmentation Strategy for Treatment of Major Depression. J. Psychiatric Pract. 2006 Jul; 12(4): 205-13.
16. MayoClinic.com. Depression and anxiety: Exercise eases symptoms. http: www.mayoclinic.com/health/depression-and-exercise/MH00043. Mayo Clinic, Accessed 30 November, 2007.
17. Department of Health and Human Services: Centers for Disease Control and Prevention. U.S. Physical Activity Statistics: Definitions.. www.cdc.gov/nccdphp/dnpa/physical/stats/definitions.htm. Accessed 30 November, 2007.
18. Department of Health and Human Services: Centers for Disease Control and Prevention. Participation in High School Physical Education---United States, 1991--2003. www.cdc.gov/mmwR/preview/mmwrhtml/mm5336a5.htm. Accessed 30 November 2007.
19. Whitaker, Robert C. et al. Predicting Obesity in Young Adulthood from Childhood and Parental Obesity. New England Journal of Medicine. 1997 337(13): 869-873.
20. American Heart Association. Children’s Need For Physical Activity: Fact Sheet. www.americanheart.org/print_presenter.jhtml?identifier=771. Accessed 30 November, 2007.
21. O’Kane, John W. et al. Prevalence of Obesity in Adult Population of Former College Rowers. J. American Board of Family Practice. 2002 Nov-Dec; 15(6): 451-454.
The obesity epidemic in the United Sates is well-documented, and the statistics are grim. In 1985, there were no states which reported an obesity rate of greater than 10-14%, and only 8 states fell into that 10-14% category (obesity being defined as a BMI of 30 or higher). In 1990, 34 states fell into the category of 10-14% obesity rate. By 2006, 4 states were in the 15-19% obesity rate category, 2 states were in the >30% category, and the remainder were quite evenly spread between 20 and 29% (1). A host of medical problems have been associated with obesity, ranging from the obvious to the surprising. These problems include heart disease and stroke, hypertension, diabetes, cancers, gallbladder disease, osteoarthritis, gout, and respiratory problems (2).
Nearly everyone has heard the rhetoric about the tried and true ways in which to combat obesity: healthy diet and exercise. However, either by accident or by design, diet receives the lion’s share of publicity about weight loss and weight maintenance. On two out of three websites for major diet programs, Atkins and South Beach, exercise is not mentioned at all in their plan (3,4). For a third diet program, Weight Watchers, exercise is mentioned, but only in passing and is not stressed (5). To be sure, a healthy diet is extremely important, but evidence from studies as well as implementation of the Social Cognitive Theory (6,7) show that increased exercise would help the problem of obesity just as much, if not more, than diet. However, there has been very little in the way of public awareness campaigns regarding exercise and its health benefits – both to help in the fight against obesity and in other areas of general health. Greater emphasis needs to be placed on the public’s awareness about the importance of exercise at every age.
The Focus On Diet Alone Is Bound To Fail—Slow Effects Lead To Lack Of Positive Reinforcement And Low Self-Efficacy
As stated above, when trying to combat obesity, the importance of diet is great. To this end, the USDA has for years relied on its promotion of the “food pyramid,” which explicitly shows how many servings of each types of foods are recommended every day to maintain a healthy diet. Categories of food groups consist of grains, vegetables, fruits, milk, and meats and beans (8). Promotion of and education about the food pyramid, while valuable, relies on the Theory of Reasoned Action. This theory aims to predict people’s behaviors (like new diets) by using their attitudes towards behaviors, the subjective norms towards behaviors, and his or her behavioral intention to carry out behaviors (9). It is based on the assumptions that a change in beliefs (such as a new-found belief that a healthy diet will help you lose weight) will lead to a change in behavior (such as an adoption of the food pyramid in making dietary decisions). Furthermore, it assumes that actions necessarily follow intentions (9). While this model certainly has useful aspects, it is fundamentally flawed in its use when it comes to the adoption of a healthy diet. Personal experience for many people, as well as common sense, says that most overweight and obese people know and believe that a healthy diet will lead to weight loss. But the acquisition of that belief does not necessarily lead to a change in eating behavior. (10). Even if an obese person intends adopt a new behavior and start following a healthy diet, the growing awareness of a healthy diet coinciding with American’s growing waistlines proves that actions in this case often do not follow intentions. A major reason for this is the time it takes for a healthy diet to take effect. Unless people are literally starving themselves, weight loss through a healthy diet alone is a slow and gradual process. It requires constant adherence, and nearly an all-day-every-day perseverance, which few people possess (10,11,12). Due to this fact, a healthy diet alone, while noble, promotes very little self-efficacy and positive reinforcement. Either people do not attempt healthy diets, because they know they cannot stick to them, or they quickly revert to their old diets. It takes a long time to see results (a reduction in Calories of 500-1000 per day will result in a drop of 1-2 pounds per week), and in the interim, grand intentions often stay intentions rather than leading to behaviors (13). Furthermore, once people fall off the wagon (a piece of birthday cake at a colleague’s party), self-efficacy lowers even further, leading to a pattern of unhealthy eating behavior.
For those people for whom the Theory of Reasoned Action initially does take hold and who change their diets to be healthier, countless studies have shown that the vast majority of people who lose weight on a lower-calorie, healthier diet eventually re-gain most or all of the weight they lost (11). For example, in a study conducted by the American Journal of Clinical Nutrition, obese men were placed on a very low calorie diet for 10 weeks, and after those 10 weeks were followed up to monitor weight gain. After being taken off the strict diet, many of the men re-gained the weight which they had lost. However, a second subset of men in the cohort were placed on the same low-calorie diet along with exercise. The two groups of men lost about the same amount of weight during the initial 10 week study phase, but after the diet phase, those who were put on the exercise program were less likely to re-gain the weight which they had lost (12). Indeed, a fact sheet from the American Medical Association (11) states that for maintaining weight loss, “weight regain is common. Combining a very low calorie diet with…physical activity…may help increase weight loss and prevent weight regain” (11).
Lack Of Focus On Exercise Fails To Recognize Its Immediate Positive Physical And Mental Effects Which Lead To High Self-Efficacy And Positive Reinforcement
The hallmark of the Social Cognitive Theory, a model for predicting behavior based on the interplay between people’s environments, behaviors and personal factors (6), is the concept of self-efficacy: people’s own senses of their abilities to adopt a new behavior. High self efficacy means that people believe a particular goal is attainable, whereas low self efficacy means that people know or believe that achievement of a goal is unlikely (7). As stated above, adoption of a new healthy diet in order to achieve weight-loss tends to little positive reinforcement. For one thing, an obese person who has just finished a low-calorie, healthy meal is unlikely to feel anything except hunger (11). Secondly, as stated before, the health and weight effects of a healthy diet are gradual, and as such, are unlikely to foster positive reinforcement. Exercise, on the other hand, has healthy diet beaten on both of these fronts (12,14).
First of all, exercise causes your body to release endorphins: hormones which give a person a natural high and general feeling of well-being (14). Personal experience shows that upon completion of exercise, whether that be a light workout or a 15-mile run, people immediately have a feeling of accomplishment and that feeling serves as positive re-enforcement for the rest of the day in terms of a healthy lifestyle. People feel physiological positive and immediate effects upon completion of exercise, which increase self-efficacy in a way that healthy eating cannot.
Secondly, exercise has immediate health effects which are indirectly related to weight loss. Studies have shown that exercise helps ease anxiety and depression (15,16). It stands to reason, therefore, that this reduction in anxiety and depression symptoms will lead to higher self-efficacy when it comes to continuing an exercise program. These positive effects feed off of each other: exercise releases endorphins and reduces depression and anxiety, which leads to higher self-efficacy in an exercise program, which reinforces the exercise program.
Lack Of Physical Education Classes In School Sets A Bad Pattern For Physical Activity Later In Life
The CDC recommends at least 30 minutes of moderate physical activity at least 5 days per week or at least 20 minutes of vigorous activity at least 3 days per week. However, the CDC reports that in 2005, there were only 7 states in which greater than 55% of the population met the recommended amount of physical activity. In four states, less than 40% of the population met the recommendations. In most states, between 40 and 55% met the recommendations (17). Furthermore, this pattern of physical inactivity begins at an early age. The CDC reports that in 2003, 52.8% of females and 58.5% of males in high school were enrolled in a physical education class. Only 34.9% of females and 43.6% of males were physically active during PE class during that same year (18).
Not surprisingly, this pattern of inactivity which begins at an early age persists later in life. A report on aging from the World Health Organization states that people who exercise early in life are more likely to exercise as adults (19). Conversely, and American Heart Association fact sheet reports that “inactive children are more likely to become inactive adults” (20).
These data are troubling, especially when examined using the framework of the Social Cognitive Theory, which includes life experience as one of its factors. The Social Cognitive Theory states that a people’s experiences in a behavior, whether that experience be successful or unsuccessful, has direct impact on their self-efficacy toward a behavior. Previous successful experience in a behavior will positively impact self-efficacy, whereas unsuccessful experience lowers it (7). This theory explains why many people may be reluctant to begin an exercise program, or have low self-efficacy in doing so. People who have led sedentary lifestyles all throughout childhood will not have positive exercise experiences to draw upon in order to increase self-efficacy, whereas people who participated in sports or physical education classes in their youth will be more likely to be comfortable using physical activity as a tool with which to combat obesity.
Indeed, a study of former college rowers conducted in the Journal of American Board of Family Practice shows that, for both men and women, incidences of obesity were significantly lower later in life than for the population at large. This indicates that people who participated in athletics in college had successful experiences with exercise, and as a result, have high self-efficacy when it comes to adopting an exercise program later in life (21).
Conclusion
Nobody contests the fact that maintaining a healthy diet is important, especially when it comes to a reduction in saturated fats, trans fats and cholesterol, in combating the obesity problem in our country. However, it is unrealistic and irresponsible to emphasize diet alone because people are bound to fall off the wagon. The focus on a healthy diet overlooks key flaws in the Reasoned Action Model, has low self-efficacy and as a result, a low success rate. One need only to look at trends in the obesity rates in America to support this notion. An exercise program is just as important, if not more important, than diet in maintaining a healthy weight. Because its immediate effects promote self-efficacy and a healthy cycle of behavior, it’s vital in the battle to combat obesity, yet too often it is overlooked and not stressed enough. The most important step we as a society can take to reverse this inactivity trend in the United States is to increase physical activity at all ages, especially in youths, both in school and outside of school. The Social Cognitive Model postulates that positive experience in a behavior leads to high self-efficacy later in life, and studies such as that of the college rowers show this to be the case. Kids need to get moving at an early age. Get them comfortable with physical activity. That way, when they gain unwanted weight later in life, they are in a position to know they have the power and ability to do something about it, and not just sink into a dangerous and possibly deadly food cycle.
References
1. Department of Health and Human Services: Centers for Disease Control and Prevention. U.S. Obesity Trends: 1985--2006. www.cdc.gov/nccdphp/dnpa/obesity/trend/maps/index.htm. Accessed 30 November, 2007.
2. WebMD. Weight Loss: Health Risks Associated With Obesity. http: www.webmd.com/cholesterol-management/obesity-health-risks. Cleveland Clinic. Accessed 30 November, 2007.
3. Atkins Phases. Atkins Advantage: The New Look of Nutrition. http://www.atkins.com/articles/atkins-phases. Accessed 30 November, 2007.
4. The South Beach Diet Online: About the Diet. http://southbeachdiet.com/public/about-the-south-beach-diet/about-the-south-beach-diet.asp?GID=201. Accessed 30 November, 2007.
5. Weight Watchers. The Flex & Core Plan. http: www.weightwatchers.com/plan/eat/plans.aspx. Accessed 30 November, 2007.
6. Bandura, A. Social learning theory. Englewood Cliffs, NJ: Prentice Hall, 1977.
7. Bandura, A. Social cognitive theory: An agentic perspective. Annual Review of Psychology. 2001; 52, 1-26.
8. Department of Agriculture. My Pyramid Plan. www.mypyramid.gov. Accessed 30 November, 2007.
9. Fishbein, M., & Ajzen, I. Belief, Attitude, Intention, and Behavior: An Introduction to Theory and Research. Reading, MA: Addison-Wesley, 1975.
10. Cachelin, FM et al. Beliefs About Weight Gain And Attitudes Toward Relapse In A Sample Of Women And Men With Obesity. Obesity Research 1998; 6(3): 231-7.
11. Department of Health and Human Services: National Institutes of Health: Weight-Control Information Network. Very Low Calorie Diets.. http://win.niddk.nih.gov/publications/low_calorie.htm. Accessed 30 November, 2007.
12. van Aggel-Leijssen, Dorien P.C., et al. Short-term effects of weight loss with or without low-intensity exercise training on fat metabolism in obese men. Am J Clin Nutr;73:523-31.
13. Department of Health and Human Services: National Heart Lung and Blood Institute: The Practical Guide: Identification,Evaluation, and Treatment of Overweight and Obesity in Adults. http://www.nhlbi.nih.gov/guidelines/obesity/prctgd_c.pdf. Accessed 30 November 2007
14. Michaels, Jillian. Exercise, Endorphins, and Your Health. Diet & Body. http://dietandbody.com/exercise/2007/08/exercise-endorphins-and-you.htm. Accessed 30 November 2007.
15. Trivedi, MH, et al. Exercise as an Augmentation Strategy for Treatment of Major Depression. J. Psychiatric Pract. 2006 Jul; 12(4): 205-13.
16. MayoClinic.com. Depression and anxiety: Exercise eases symptoms. http: www.mayoclinic.com/health/depression-and-exercise/MH00043. Mayo Clinic, Accessed 30 November, 2007.
17. Department of Health and Human Services: Centers for Disease Control and Prevention. U.S. Physical Activity Statistics: Definitions.. www.cdc.gov/nccdphp/dnpa/physical/stats/definitions.htm. Accessed 30 November, 2007.
18. Department of Health and Human Services: Centers for Disease Control and Prevention. Participation in High School Physical Education---United States, 1991--2003. www.cdc.gov/mmwR/preview/mmwrhtml/mm5336a5.htm. Accessed 30 November 2007.
19. Whitaker, Robert C. et al. Predicting Obesity in Young Adulthood from Childhood and Parental Obesity. New England Journal of Medicine. 1997 337(13): 869-873.
20. American Heart Association. Children’s Need For Physical Activity: Fact Sheet. www.americanheart.org/print_presenter.jhtml?identifier=771. Accessed 30 November, 2007.
21. O’Kane, John W. et al. Prevalence of Obesity in Adult Population of Former College Rowers. J. American Board of Family Practice. 2002 Nov-Dec; 15(6): 451-454.
Labels: Nutrition, Obesity, Physical Activity, Purple
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