The Obesity Epidemic

Overweight and obesity have become an epidemic in the past two decades, affecting about one billion people around the world today. Although the problem is most severe in developed countries, it is not limited to the developed world, as evidenced by the “under-nutrition” and “over-nutrition” that co-exist in developing countries. Increased prevalence of childhood overweight and obesity and related co-morbidities are perhaps most disturbing from the standpoint of the future. The economic costs of excess body weight and related co-morbidities are astronomical and will continue to rise. Today, unfortunately, there are more questions than answers regarding why we have this crisis and what we should do about it. Balancing the energy equation to attain and maintain a healthy body weight seems a simple concept, yet putting this concept into practice in everyday life has, for many, apparently become a losing battle.

What is obesity?
There are various methods to determine whether a person is overweight or obese, but the most commonly used is body mass index (BMI). In adults, BMI is calculated by dividing a person’s body weight (in kg) by the square of the height in meters. Overweight is defined as a BMI of 25 to 29.9, and obesity is defined as a BMI of 30 or greater. In children, overweight and obesity is determined from the pediatric growth charts for the U.S. population (http://www.cdc.gov/growthcharts). A BMI between the 85th and 95th percentile for age and sex is considered at risk for overweight, and a BMI at or above the 95th percentile is considered overweight or obese (AAP 2003).

Epidemiology of obesity
The World Health Organization (WHO) estimates that there are one billion overweight and obese people in the world, with about 300 million of them being obese (WHO 2002). In the U.S. in particular, the increasing trend of overweight and obesity is staggering. According to the results of the 1999–2000 National Health and Nutrition Examination Survey (Flegal et al. 2002; NCHS 2002), 64 percent of the U.S. adult population is overweight; about half of this population is classified as obese, which represents a doubling in the prevalence of obesity in adults in the past 20 years.

Perhaps more alarming than the trend in adults is the increasing trend toward overweight in children. From 1999-2000 data, about 30 percent of children and adolescents ages 6 to 19 years old are overweight or at risk of overweight (Ogden et al. 2002; CDC 2003a). About half of these children are overweight, representing a doubling to tripling of the prevalence of overweight in these age groups in the past two decades. The rates of overweight and at risk of overweight are even higher among minorities and economically disadvantaged children. For example, the rates of overweight and at risk of overweight exceed 40% among 12-19 year old non-Hispanic blacks and Mexican Americans.

According to the U.S. Surgeon General (2001), about 300,000 deaths per year in the U.S. are attributable to obesity, and obese individuals have a 50–100 percent increased risk of premature death from all causes compared to people with a healthy body weight.

What causes obesity?
Overweight and obesity are very complex conditions, with numerous contributing factors, such as genetics, metabolism, behavior, the environment, culture, and socioeconomic class (Office of the Surgeon General 2001). A few genetic diseases (e.g., Prader-Willi syndrome) and medical conditions (e.g., Cushing’s disease) are associated with obesity, but in most situations, body weight is a matter of balancing the energy equation of calories consumed (eating) and calories expended (physical activity).

Although obesity has been viewed by some as a character flaw (e.g., lazy, weak) or the result of bad habits (e.g., eating when not hungry to satisfy emotional needs, eating in front of the TV), recent research supports the view that, in developed countries, weight gain and obesity are an “inevitable outcome of the mismatch between our evolutionary endowment and modern lifestyles” (Lowe 2003). Our current environment has been termed “obesigenic” because of a reduction in required energy expenditure resulting from technological advances in our everyday lives and the ready availability of good tasting, relatively inexpensive, calorie-dense food.

Several food-related factors may be at play in the obesity epidemic (Peters 2003), including a greater number of meals eaten away from home, a broader variety of “fast foods,” the relatively higher energy density of foods that are popular today, and a decrease in the cost of food as a proportion of disposable income. In addition, food portion sizes have increased over the last 25 years (Nielsen and Popkin 2003), and Rolls and coworkers (2002; Kral et al. 2002) have demonstrated that total energy intake increases when people are offered larger portions. Other food-related issues currently circulating include the “supersizing” of serving portions (Rolls 2003), caloric content of fast food, advertising, especially that targeted at children, availability of sugar-sweetened soft drinks in school cafeterias, and the “demonization” of certain specific foods (i.e., “good” foods vs. “bad” foods), notably sugar-sweetened, carbonated soft drinks, by some public health officials and activists groups. “Addiction” to food has also become an area of interest for future research.

Today’s sedentary lifestyles have also been cited as a major factor in the increasing prevalence of obesity. The WHO (2002) estimates that physical inactivity causes 1.9 million deaths globally and is related to about 10–16 percent each of cases of breast cancer, colon and rectal cancers, and diabetes, and about 22 percent of cases of ischemic heart disease. The problem of physical inactivity has been most concerning in children. It has been reported that 20 percent of U.S. schoolchildren ages 8–16 years have two or fewer periods of vigorous exercise a week, while more than 25 percent watch at least four hours of television per day (AAP 2003). It is not surprising that children who watch four or more hours of television per day have higher BMIs than those watching two or fewer hours of television per day.

Obesity-related diseases
Excess body weight is strongly associated with type 2 diabetes, cardiovascular disease, cancer, arthritis, breathing disorders, and psychiatric disorders such as depression (CDC 2003b). Recently, it was reported that obesity is associated with increased death rates from all cancers combined as well as cancers at multiple specific sites; the heaviest adult men and women (BMI 40 and greater) had 52 percent and 62 percent higher risk of death from cancer, respectively, compared to men and women of normal weight (Calle et al. 2003). Co-morbidities in children have also increased at an alarming rate. For example, until recently, type 2 diabetes was rare in children, but its prevalence has been rising along with that of overweight and obesity in children.

Treatment of obesity
Studies have shown that even a modest weight loss of about 5–15 percent of body weight by overweight and obese individuals can reduce the risk for some diseases, especially cardiovascular disease (Office of the Surgeon General 2001). However, weight loss and especially maintenance of weight loss are major challenges; there is no “magic bullet.” The standard of weight loss programs has been a multidisciplinary approach including low calorie diets, exercise, and behavior modification. Such programs are effective in acute weight loss. Sadly, however, most patients eventually regain the weight they lost.

To date, the scientific consensus has been that all calories, regardless of source, are the same. However, the recent popularity of the “Atkins” diet with high-protein and low-carbohydrate intake and the “low carb” craze has raised questions about this assumption and has prompted further ongoing research.

Current pharmaceutical approaches to weight loss include sibutramine, which works on brain neurotransmitters to reduce food intake and hunger, and orlistat, which reduces breakdown of fat in the gastrointestinal tract with a consequent reduction in fat absorption. For the severely obese, gastric bypass surgery has become more common with remarkable success in reduction of excess body weight and related co-morbidities.

Conclusions
There is much yet to be learned regarding the various contributing factors for overweight and obesity and what strategies will be effective in reversing this trend. According to Peters (2003), although much is known about the factors contributing to obesity, scientific evidence is lacking to apportion a role for each of these factors in the obesity epidemic that has been building over the last two decades. Further, according to Jeffery and Utter (2003), “…there is genuine uncertainty in the scientific community about how the energy imbalance leading to increased national body weight is occurring.”

Recognizing the daunting task ahead and the critical need for scientific and public policy answers, Exponent has assembled a multidisciplinary team to work with clients on a comprehensive approach to the global overweight and obesity crisis. The Exponent team has professional expertise in medicine (e.g., internal medicine, pediatrics, occupational medicine, and preventive medicine), epidemiology, public health, statistics/biostatistics, nutrition, nutritional biochemistry, social psychology, experimental cognitive psychology, kinesiology, exercise physiology/fitness, and physical education. These experts have experience in the following areas:

Research

• Controlled clinical trials
• Descriptive and analytical epidemiology studies
• Statistical evaluation of large databases
• Survey design and management, including questionnaire development

Evaluations

• Dietary intake
• Health economics
• Health outcomes
• Public health
• Health risk and risk apportionment

Literature reviews

• Targeted searches and reviews
• Evaluation of scientific validity of published studies
• Preparation of summary reports

Food regulatory and government affairs

• Preparation and submission of health claims and qualified health claims
• Interactions with government agencies regarding proposed product claims

Scientific issues management

• Issue evaluation and strategy development
• Development of scientific and medical advisory boards
• Mobilization of key scientific and medical experts globally

Health communication

• Development of materials for health care professionals and consumers
• Liaisons with key organizations
• Scientific and lay presentations
• Media interviews

Liability management

• Development of scientific strategy
• Scientific and medical expert testimony.

In addition, because overweight and obesity are global issues, Exponent has developed networks of key opinion leaders in scientific and medical disciplines related to obesity in countries around the world to work with clients on local issues. For more information, contact Harriett Butchko, M.D. at hbutchko@exponent.com or (630) 274-3221.

References:

American Academy of Pediatrics (AAP). Prevention of Pediatric Overweight and Obesity. Policy Statement. Pediatrics 2003; 112(2): 424-430.

Calle, EE, Rodriguez, C, Walker-Thurmond, K, and Thun, MJ. Overweight, Obesity, and Mortality from Cancer in a Prospectively Studies Cohort of U.S. Adults. New Engl J Med 2003; 348(17): 1625-1638.

Centers for Disease Control and Prevention (CDC). Nutrition, Physical Activity, and Obesity Prevention Program. Resource Guide for Nutrition and Physical Activity Interventions to Prevent Obesity and Other Chronic Diseases. 2003a.

Centers for Disease Control and Prevention (CDC). Nutrition and Physical Activity. 2003b; www.cdc.gov.

Flegal, KM, Carroll, MD, Ogden, CL, and Johnson, CL. Prevalence and trends in obesity among US adults, 1999-2000. JAMA 2002; 288(14):1723-1727.

Jeffery, RW, and Utter, J. The Changing Environment and Population Obesity in the United States. Obesity Research 2003; 11(supplement): 12S-22S.

Kral, TVE, Roe, LS, Meengs, JS, Wall, DE, Rolls, BJ. Increasing the portion size of a packaged snack increases energy intake. Appetite 2002; 39:86.

Lowe, MR. Self-regulation of Energy Intake in the Prevention and Treatment of Obesity: Is It Feasible? Obesity Research 2003; 11(supplement): 44S-59S.

National Center for Health Statistics (NCHS). Prevalence of Overweight and Obesity Among Adults: United States, 1999-2000. 2002; www.cdc.gov/nchs

Neilsen, SJ, and Popkin, BM. Patterns and Trends in Food Portion Sizes, 1977-1998. JAMA 2003; 289: 450-453.

Office of the Surgeon General. The Surgeon General’s Call to Action to Prevent and Decrease Overweight and Obesity 2001. Rockville, MD.

Ogden, CL, Flegal, KM, Carroll, MD, and Johnson, CL. Prevalence and trends in overweight among US children and adolescents, 1999-2000. JAMA 2002; 288(14):1728-1732.

Peters, JC. Combating Obesity: Challenges and Choices. Obesity Research 2003; 11(supplement): 7S-11S.

Rolls, BJ, Morris, EL, and Roe, LS. Portion Size of Food Affects Energy Intake in Normal-weight and Overweight Men and Women. Am. J. Clin. Nutr 2002; 76: 1207-1213.

Rolls, BJ. The Supersizing of America. Nutrition Today 2003; 38(2): 42-53.

World Health Organization (WHO). The World Health Report 2002. Reducing Risks, Promoting Healthy Life. Geneva.

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