Childhood Obesity: Causes, Effects, and Prevention Strategies

The intent of this research study is an examination of the physiological and psychological effects of obesity among American children. Through qualitative examination, the researcher observes what factors contribute to obesity, with particular emphasis on genetic, environmental, and parental factors. In addition, the researcher examines the nutritional and dietary habits of youths in order to determine what factors are most likely to contribute to the growing epidemic striking this nation's youth, with in-depth investigation into the effects of obesity among children.

This research is relevant for a number of reasons. There is a growing body of evidence suggesting that young Americans are getting wider, to the point where their lives and their mental health are at stake (Crute, 2005). An epidemic has hit the United States, with an alarming rise in childhood obesity — a problem that may actually begin during the toddler years, as more and more children turn to television rather than outdoor activity for entertainment (Tweedie, 2004).

Studies suggest that one in five toddlers is already overweight by the time they reach their fourth birthday (Tweedie, 2004). Overweight toddlers typically become overweight adolescents, facing increased risks for stroke, heart disease, asthma, diabetes, and even abnormalities of foot structure as a result of excessive weight (Tweedie, 2004). Problems in adolescents include poor self-esteem, fears of being unpopular and unattractive, depression, and — perhaps most seriously — eating disorders (Tweedie, 2004).

Many studies have focused on single causes of obesity in children, including poor dietary habits and inactivity (Tweedie, 2004). The intent of this research study is to provide a more comprehensive examination of the physiological and psychological factors that contribute to childhood obesity. The researcher also identifies what the effects of obesity are in children, both physiologically and psychologically.

The researcher addresses the following questions: (1) What combination of physiological and psychological factors is most likely to contribute to obesity? (2) What are the combined physiological and psychological effects of obesity in children? To answer these questions, the research focuses on an investigational analysis of all combined factors — including genetic, environmental, and parental — that may contribute to obesity in youths. From the information gathered through the literature review and field research, the researcher intends to produce a theory grounded in research that not only explains but also helps provide avenues for addressing the epidemic affecting this nation's children.

Obesity rates among American youth have soared to crisis levels over the past ten years, and the impact is evident in homes across the nation. According to Blasi (2003), obesity is considered "the number one health risk for children in the United States today" (p. 321). The number of children classified as overweight has more than doubled in the last twenty to thirty years, with approximately one in five children defined as overweight by health standards (Blasi, 2003). Even though 20 to 30% of children can be classified as obese, the condition remains largely underdiagnosed and undertreated by many healthcare practitioners and families (Blasi, 2003). Some studies suggest that if a child is overweight by the time they reach age six, they are more than 50% likely to be obese when they reach adulthood (Blasi, 2003; Axmaker, 2001).

America's children are literally expanding each and every day. Young adolescents once carrying only small amounts of baby fat have been replaced by obese fifth graders. More and more middle and high school students are diagnosed with diabetes and increased risk factors for cancer, stroke, and heart disease (Crute, 2005; Tweedie, 2004). Health experts are calling it a national crisis; obesity is affecting children's education as well as their quality of life and life expectancy (Ogden, 2002).

The percentage of children and adolescents who are overweight or obese is now at its highest. Approximately 25% of children and adolescents are considered overweight, a figure that has doubled in the last 30 years (American Obesity Association, 2000). Among boys between the ages of 6 and 11, obesity rates have tripled during the last two decades, and increased more than two-and-a-half times for girls. Obesity is also associated with many adverse health effects including asthma, diabetes, hypertension, sleep apnea, psychosocial consequences, and increased risk of morbidity and mortality (American Obesity Association, 2000).

Because obesity is associated with chronic disease and adverse health outcomes, the growing incidence of obesity in the population has become a serious public health concern. This study is significant because it contributes to the current body of research aimed at overcoming this national crisis.

Obesity rates are rising among the nation's youth due to a variety of complex factors. One of the more commonly cited contributors to the obesity epidemic is inadequate participation in active sports, among both female and male young children (Tweedie, 2004).

According to the National Association of State Boards of Education (2004), only 8% of elementary schools, 6% of middle schools, and 6% of high schools required daily physical education classes. There was a time when all children were required to actively participate in physical education; this is no longer the case. When children are encouraged to participate, they are often given the message that winning is ultimately the most important aspect of play, rather than fun, health, and fitness.

The National Center for Health Statistics (2004) reported that nine million children over the age of six are obese. Another 15% are overweight and borderline "at risk." Data from the Institute of Medicine (2004) reported that 13% of Caucasian children ages 12 to 19 are overweight, 21% of African-American children ages 12 to 19 are overweight, and 23% of Mexican-American adolescents are overweight.

Environmental factors and genetics are two major contributors to childhood obesity, although physical educators nationwide have also observed the effects of individual behaviors and family dynamics resulting in poor nutrition choices and lack of exercise. Jerry Newberry, executive director of the National Education Association (NEA), was quoted in NEA Today (March 2005): "If kids aren't healthy, their learning suffers." This statement suggests that learning is suffering across the nation.

Part of the problem may be the inordinate amount of fast food that young people consume. According to Moran (1999), "thirty-three percent of adolescents eat fast food every day." Research shows that sedentary adolescents who eat high-sugar and high-fat meals have poorer cognitive skills, higher anxiety levels, and problems with hyperactivity. Unhealthy adolescents also tend to miss school more often.

NEA Today (March 2005) found that schools in every state had reported that "tens of millions of dollars" were lost because of absenteeism caused by inactivity and poor nutrition (Crute, 2005). Interestingly, despite this finding, few researchers have examined what effect, if any, a nutritional education program might have on childhood behaviors.

There are emotional downsides to childhood obesity as well. As a physical educator with 12 years of experience, the researcher has witnessed obese children who could not play sports, who could barely fit into their desks at school, and who could not get through a school day without being bullied by peers. "The psychological risks can be as great as the physical risks," says Ted Feinberg, assistant executive director of the National Association of School Psychologists. "Low self-esteem and depression can undermine children's learning, behavior, and well-being" (Moran, 1999).

The most immediate consequence of being overweight during childhood and adolescence is psychosocial (Dietz, 1998). The social implications of obesity are a major problem area that is often neglected. "The obese do less well academically, have poorer job prospects and lower self-esteem. The latter is often caused by repeated failures at weight loss" (Dietz, 1998). Obese children are often taller than their non-overweight peers and are apt to be viewed as more mature — an inappropriate expectation that may result in adverse effects on their socialization (Dietz, 1998). Overweight children and adolescents report negative assumptions made about them by others, including being inactive or lazy, being strong or tougher than others, not having feelings, and being unclean (American Obesity Association, 2000).

This epidemic did not occur overnight. Obesity and overweight are chronic conditions.

This study was concerned with genetics, family dynamics and parenting, and nutrition and dietary intake — all three of which contribute to childhood obesity. Specifically, the researcher attempts to determine what factors are contributing to the nation's epidemic rise in obesity among children, and what the effects are of the growing girth plaguing the nation's children. The objective of the research is the development of a concrete theory that clearly defines the effects of all contributing factors, with the intent of providing healthcare providers and researchers with new avenues for exploring the epidemic affecting this nation's children.

The purpose of this study was to survey 50 K–12 physical educators in order to determine their perceptions of the unintended physiological and psychological consequences of childhood obesity in their classrooms over tenures ranging from 3 to 30+ years. In doing so, the researcher aims to provide clear information that may help guide future research related to childhood obesity.

Obesity — a state or condition present in the body resulting in abnormal levels of fat. The term is typically used for people who are more than 20 to 30% overweight for their combined sex, age, and height (Crofton, 2005). Obesity may also be defined as being over 100 pounds above normal body weight. It is considered a level above overweight and is typically associated with symptoms including fatigue, depression, and problems with compulsive eating (Crofton, 2005).

Physiological — the biological effects of a given phenomenon or substance.

Psychological — the emotional and mental effects of a given phenomenon or substance.

Psychosocial — the combined social and emotional effects of a given phenomenon. Relates to how individuals perceive themselves and their place in the world. Psychosocial factors can influence one's self-esteem and may include society's perceptions that overweight or obese people are lazy, inefficient, and poor learners (Tweedie, 2004).

There are a variety of factors and many theories that play a role in childhood obesity, making it a complex issue to address. It is vital that researchers examine obesity and its impact on children from a variety of different perspectives in order to gain a clear and accurate picture of how and why the problem is occurring.

For the purpose of this paper, a concentrated review of literature was conducted focusing specifically on the following factors: the role of genetics, family dynamics and parenting, and nutritional choices. The researcher assumes that all three of these factors inherently contribute to childhood obesity, based on the preliminary data presented in this review.

Studies from a variety of disciplines — including pediatric nutrition and epidemiology — demonstrate that childhood obesity is not caused by any single thing; rather, "obesity has a multifactorial origin" (Gable & Lutz, 2000). Some of these factors include genetic disposition, family demographics, parenting beliefs and practices, child television viewing and computer use, physical activity, "food as reward," increasingly hectic family lifestyles, and the abundance of large-portion, high-fat foods.

One particular theory holds that obesity is a result of an imbalance of energy. "This epidemic is a result of energy imbalance over a long period of time" (Strauss, 2005). Energy balance functions like a scale: when calories consumed are greater than calories used, weight gain results. Overweight conditions and obesity result from this energy imbalance. According to Richard S. Strauss, MD, the relationship can be summarized as follows:

Weight gain: Calories consumed > Calories used
Weight loss: Calories consumed < Calories used
No weight change: Calories consumed = Calories used

Weight gain involves eating too many calories and not getting enough physical activity (Strauss, 2005). The cause of energy imbalance for each individual may be due to a combination of several factors. "A person's body weight," according to Strauss (2005), "is the result of genes, metabolism, behavior, environment, culture, and socioeconomic status."

The most common method for determining whether adults or children are overweight or obese is the body mass index (BMI) (Grantmakers in Health, 2001).

Body Mass Index = (Weight in pounds × 703) ÷ (Height in inches × Height in inches)

Because BMI for children is expected to increase as they grow, an overweight classification cannot be based on a single number. Rather, the determination of whether a child is overweight is a function of age- and sex-specific percentiles based on the Growth Charts for the United States issued by the Centers for Disease Control and Prevention (CDC) in May 2000 (Grantmakers in Health, 2001). Children with a BMI above the 95th percentile for their age and sex are considered overweight. Those between the 85th and 95th percentile are considered at risk of being overweight. The terms "obese" and "overweight" are often used interchangeably, but both refer to children above the 95th percentile (Grantmakers in Health, 2001).

The Office of Genetics and Disease Prevention (2005) found that fat stores are regulated over a long period of time by complex systems that involve input and feedback from fatty tissues, the brain, and endocrine glands such as the pancreas and the thyroid. Overweight and obesity can result from only a very small positive energy imbalance sustained over a long period of time (Office of Genetics and Disease Prevention, 2005).

Strauss notes that behavior and environment play a large role in causing people to become overweight or obese. These are, according to many researchers, the greatest areas for prevention and treatment actions (Strauss, 2005). "Genetics and the environment may increase the risk of personal weight gain. However, the choices a person makes in eating and physical activity also contribute to overweight and obesity" (Strauss, 2005).

"A person's body weight is regulated by numerous physiological mechanisms that maintain balance between energy intake and energy expenditure" (Strauss, 2005). Under normal conditions, these systems are extraordinarily precise; for example, a positive energy balance of only 120 kcal per day — approximately one serving of a sugar-sweetened soft drink — would produce a 50-kg increase in body mass over ten years. Therefore, any factor that raises energy intake or decreases energy expenditure by even a small amount will cause obesity in the long term.

Bourbeau, Crawford, Freeman et al. (2005) suggest that rapidly declining rates of sports participation among youths have contributed to the obesity epidemic. The researchers identify several underlying trends contributing to this decline: (1) personnel issues, including the number of teachers and coaches supporting intramural programs; (2) facility issues, including problems securing space to meet student demand; and (3) cultural issues, which either pressure children to play numerous competitive sports at once or to do nothing at all (Bourbeau, Crawford & Freeman, 2005, p. 11).

There are also many behaviors and amusements that children currently engage in that have contributed to youth obesity rates, including sedentary entertainments such as video games, computer media, television, MP3 players, and cell phones — all of which promote inactivity at a young age (Bourbeau, Crawford & Freeman, 2005).

The physical effects of obesity have been well documented. Children who are obese are at greater risk for lifelong health problems including heart disease, stroke, high blood pressure, Type II diabetes, and orthopedic problems resulting from increased stress on the joints and bones (Hoot, 2004; Blasi, 2003; Tweedie, 2004; Crute, 2000). More devastating than the physical complications, however, are the psychosocial effects of being overweight. Children who are overweight are more likely to suffer negative emotional consequences. Generally, children tend to "develop negative attitudes about overweight peers" early in life; such attitudes often result in the stigmatization of overweight children (Hoot, 2004). Overweight children are more often thought of as "lazy, stupid, slow, and self-indulgent" (Hoot, 2004, p. 70). They are also more likely to be perceived by other children as less likeable, which typically results in exclusion from "social development opportunities" including play (Hoot, 2004, p. 70).

Studies have shown that obese children are more likely to experience depression and low self-esteem (Hoot, 2004; Blasi, 2003) and more likely to be socially withdrawn than other children (Hoot, 2004). These trends are noted in children as young as ages 4 and 5 (Davison & Birch, 2001; Hoot, 2004).

There is a substantial body of evidence confirming a genetic influence on obesity rates. Bouchard (1990) notes that "not all children who eat non-nutritious foods, watch several hours of television daily, and are relatively inactive develop obesity. Genetics have recently been shown to influence fatness, regional fat distribution, and response to overfeeding."

Ebbeling, Ludwig, and Pawlak (2002) point out that genetic factors can have a tremendous impact on an individual's predisposition for becoming obese or overweight. The Lancet published a report in 1997 about two massively obese Pakistani children who were found to have a mutation in the gene encoding leptin — a hormone normally produced by adipocytes and secreted in proportion to body-fat mass (Ebbeling, Ludwig, & Pawlak, 2002). Since that finding, "five genetic mutations that cause human obesity have been identified, all presenting in childhood" (Ebbeling, Ludwig, & Pawlak, 2002). Many additional candidate alleles — such as those in the variable nucleotide tandem repeat region of the insulin gene — have been discovered that appear to affect the risk of early-onset obesity (Ebbeling, Ludwig, & Pawlak, 2002).

According to The Lancet, single-gene defects account for only a small fraction of human obesity. It is very rare for people to have single-gene mutations causing severe obesity beginning in infancy, although the Office of Genetics and Disease Prevention (2005) notes that "studying these individuals is providing insight into the complex biological pathways that regulate the balance between energy input and energy expenditure." Ebbeling, Ludwig, and Pawlak (2002) found that predisposition to obesity appears to result from a complex interaction among at least 250 obesity-associated genes.

The CDC labels obesity as a condition that results from an environment of caloric abundance and relative physical inactivity, modulated by a susceptible genotype. There are some rare obesity syndromes caused by single-gene mutations, but the CDC's findings confirm that the greatest proportion of human obesity is not due to single-gene mutations. Genetic predisposition may not be health destiny, but studies indicate that inherited genetic variation is an important risk factor for obesity (CDC, 2005). Evidence from twin, adoption, and family studies strongly suggests that biological relatives exhibit similarities in the maintenance of body weight. Genetic factors are also implicated in the degree of effectiveness of diet and physical activity interventions for weight reduction (CDC, 2005). Each genetic variation may contribute a small amount of risk and may interact with environmental elements to produce the clinical condition of obesity (CDC, 2005).

The Office of Genetics and Disease Prevention (2004) found that biological relatives tend to resemble each other in body weight. Individuals with a family history of obesity may be predisposed in ways that make prevention especially important. Another finding indicates that individuals in environments of constant food intake and physical activity respond differently: some people store more energy as fat in an environment of excess, while others lose less fat in an environment of scarcity. These different responses are largely due to genetic variation between individuals (Office of Genetics and Disease Prevention, 2005).

Whitaker and Dietz (1998) suggest that prenatal over-nutrition might affect the lifelong risk of obesity. Their hypothesis stated that maternal obesity increases the transfer of nutrients across the placenta, inducing permanent changes in appetite, neuroendocrine functioning, or energy metabolism. Results of their observational studies showed a direct relationship between maternal obesity, birth weight, and obesity later in life; however, "the relative contributions of shared maternal genes vs. intrauterine factors are difficult to differentiate" (Ebbeling, Ludwig, & Pawlak, 2002). Findings in animal studies indicate long-term consequences of maternal obesity — the offspring of female rats with diet-induced obesity were heavier than offspring of rats with the same genotype but without obesity. These findings suggest that the obesity epidemic could accelerate through successive generations, independent of further genetic or environmental factors (Ebbeling, Ludwig, & Pawlak, 2002).

In addition, infants born to overweight mothers have been found to be less active and to gain more weight by age three months when compared with infants of normal-weight mothers (Bouchard, 1990).

The Lancet (2002) also stated that under-nutrition at important stages of fetal development could induce permanent physiological changes that result in obesity. For this reason, the nutrition transition could place many children in developing nations at particularly high risk of obesity (Ebbeling, Ludwig, & Pawlak, 2002). If these are the possibilities for obesity, an opportune time to initiate prevention would be before conception.

Children who were bottle-fed appear to be more at risk of obesity later in childhood than those who were breastfed (Ebbeling, Ludwig, & Pawlak, 2002). This relationship was explained in relation to permanent physiological changes caused by some intrinsic factor unique to human milk, or to psychological factors such as locus of control over feeding rate (baby vs. parent) or taste preference (Ebbeling, Ludwig, & Pawlak, 2002).

Research has shown that during early childhood, BMI normally decreases until ages 5–6 years and then increases throughout adolescence (Ebbeling, Ludwig, & Pawlak, 2002). "The age at which this BMI redirection occurs has been termed the adiposity rebound" (Ebbeling, Ludwig, & Pawlak, 2002). Several observational studies have described an increased risk for obesity later in life in individuals who experience early adiposity rebound; however, the biological importance and predictive value of this association remains a matter of debate (Ebbeling, Ludwig, & Pawlak, 2002).

For children who are predisposed to gain weight, preventing obesity is the best course (Office of Genetics and Disease Prevention, 2005). Predisposed individuals may require individualized interventions and greater support to successfully maintain weight. Strauss (2005) points out that a child's genes are not necessarily his or her destiny — obesity can be managed in many cases with a combination of diet, physical activity, and medication (Office of Genetics and Disease Prevention, 2005).

Children cannot change their genes, but they can change their behavior. The public messages aimed at preventing children from becoming overweight emphasize a nutritious diet and daily physical activity. Many who follow this advice from the outset are able to maintain a healthy weight, even with genetic susceptibility to weight gain. However, these lifestyle interventions have a range of uptake and effectiveness, especially when obesity is already present. Public health interventions aimed at the general population are not a complete solution (CDC, 2005).

Of the many factors associated with overweight and obesity, studies suggest that parenting and family dynamics perhaps play the largest role in a child's development and propensity for developing obesity. The ecosystems model recognizes relationships between and among individuals, families, psychosocial groups, institutions, and society — all of which may contribute to an individual's tendency toward obesity (Caple & Salicido, 1995). Gable and Lutz (2000) point out that "ecological theory posits that some of the potential risk factors that directly touch obese children are associated with aspects of family dynamics."

For example, research indicates that food choices are related to the demographic characteristics of the family. Single-parent households and households in which both parents work full time tend to favor the consumption of prepared foods, which tend to be high in sodium and fat (Crockett & Sims, 1995). Household income also indirectly influences children's eating habits and weight. "Between 1977–1978 and 1987–1988, lower-income households reduced their vegetable consumption by twenty-two percent, as compared to twelve percent in high-income households" (Lutz, Blaylock, & Smallwood, 1993). These findings suggest that healthy foods are expensive and require more time to prepare. Dual-worker or single-parent households may not have the time to prepare healthy meals, and low-income families may not have reliable sources of income to regularly provide healthy foods. Although food availability in the home sets the stage for eating habits, that availability is often affected by parents' time and income levels (Lutz, Blaylock, & Smallwood, 1993).

Parents' beliefs about children's nutritional needs and their attitudes toward mealtimes can also make a difference in children's weight. A common response to a child's increasing weight is to restrict non-nutritious foods. Yet, when a child's intake is restricted, profound negative consequences can result. Gingras (2000) shows that establishing food restrictions can actually have a detrimental effect on a child's natural ability to regulate food choices and feelings of satiety. By enforcing rigid guidelines, parents alter their child's responsiveness to internal signals of hunger and satiety. When parents impose eating practices with few opportunities for children to learn self-control, children learn to depend on external signals — such as looking at a clock to determine hunger, or overeating comfort foods as a way of coping with stress. Parents need to learn to trust their children to eat when hungry and to stop once they feel satisfied. It remains the parent's responsibility, however, to provide healthy food choices at appropriate times. Whether a child learns to appreciate the role of healthy foods in their well-being and to recognize their body's signs of hunger and fullness is linked to the nutrition and mealtime environment created by parents (Gable & Lutz, 2000).

The rapid advancement of society has systematically eliminated the need for physical exertion. "Children are spending more time at home watching television, sitting in front of computer screens, and playing video games, drastically reducing the amount of time they spend actively engaged in physical activities" (Henry J. Kaiser Family Foundation, 2004). During the same period in which childhood obesity has increased so dramatically, there has also been an explosion in media targeted at children. TV shows and videos, specialized cable networks, video games, computer activities, and Internet websites are now directed at children more than ever before (Henry J. Kaiser Family Foundation, 2004). "Children today spend an average of five-and-a-half hours a day using media — the equivalent of a full-time job, and more time than they spend doing anything else besides sleeping" (Henry J. Kaiser Family Foundation, 2004).

Research examining dual-income and single-parent households suggests that single parents are under more stress and spend less time at home than two-parent, single-income families (Bianchi, 1995). Children in these households spend more time on household tasks and may more frequently prepare their own meals consisting of packaged food items, or spend more time unsupervised engaging in sedentary activities (Bianchi, 1995).

"Parental modeling is crucial to the eating behaviors of children as well as self-esteem and body image" (Henry J. Kaiser Family Foundation, 2004). When parents react negatively to their own body weight, children learn that the body of the person they love and admire is somehow unacceptable — a potentially dangerous lesson. Proponents of a family perspective contend that individuals develop a normal or distorted body image in the context of family life (Hawthorn-Hoeppner, 2000). In homes where talk about weight is prominent and a focus on dieting is central, distorted cultural attitudes tend to arise. Derogatory statements related to weight and nutrition can negatively impact children. These types of homes serve as defining mechanisms for the construction of collective identity; they create a common outlook on the value of being thin. This discourse on weight can lead to dysfunctional consequences such as binge eating, food hiding, and eating disorders (Hawthorn-Hoeppner, 2000).

"With many overweight children, it isn't the extra pounds but the parent reaction to the pounds that takes the greatest emotional toll" (Hawthorn-Hoeppner, 2000). As a result, parents face a balancing act of helping the child without giving the impression that they are not loved unconditionally. A useful model for explaining parental influence on a child's behavior is the expectancy-value model of Eccles and Harold (1991), in which socialization behaviors are thought to be influenced jointly by parental expectations for the child's success in a given area and the value parents place on that success. Parents who expect their child can be successful — and who value success in an area — will be more likely to influence their children to pursue that behavior (Henry J. Kaiser Family Foundation, 2004).

Four socialization variables influence physical activity behaviors in children, according to Welk (1999): (a) Parental Encouragement — obvious verbal and non-verbal encouragement for a child; (b) Parental Involvement — the parent provides direct assistance or participation in the child's activity, such as family walks or playing catch; (c) Parental Facilitation — efforts made by parents to make it easier for children to be physically active, such as providing access to facilities or equipment; and (d) Parent Role Modeling — the parent models an active lifestyle, promoting self-efficacy and signaling that physical activity is valued (Welk, 1999).

With regard to nutrition and dietary intake, data indicate that Americans are consuming more calories but are not compensating with increased physical activity (Public Health Reports, 2000). According to the U.S. Department of Agriculture (USDA), Americans in the 1990s were consuming more food and several hundred more calories per day than they did in the 1970s. Much of this increase can be associated with eating away from home. A study by McCrory and colleagues (1999) found that an increasing proportion of household food income was spent on food prepared away from home, and that frequently eating restaurant food was associated with being overweight. In two-career families where no one is available to prepare healthy meals, warming up packaged foods, picking up fast food, or dining out has become the norm (Grantmakers in Health, 2001). As a result, the number of meals eaten outside the home has nearly doubled over the past few decades. According to the USDA, food prepared away from home provided 34% of total food consumption in 1995, up from 19% in the late 1970s (Grantmakers in Health, 2001).

When eating out, people tend to eat more or choose higher-calorie foods than they do at home (Putnam, 1999). Food eaten outside the home is, on average, higher in fat and lower in micronutrients than food prepared at home (Lin, Frazzo, & Guthrie, 1999). As people spend more time and money eating away from home, their expectations regarding volume and value have created a demand for portion sizes that are not healthy. In 1957, an average muffin was 1.5 ounces, compared to at least 5 ounces in 1997. A theater serving of popcorn was 3 cups in 1957, compared to 16 cups in 1997. The average size of a soda was 8 ounces in 1957, compared to 32 ounces in 1997 (Putnam, 1999). Susan Zepeda, Ph.D., executive director of the Health Care Foundation for Orange County, noted that "the one factor driving the increases in portion sizes in restaurants is that it allows owners to justify price increases without adding much to their overall costs" (Grantmakers in Health, 2001).

Another important contributing factor is the proliferation of high-calorie convenience foods. Americans are eating more fast food and other foods high in fat and sugar content — including prepackaged foods, cookies, chips, candy, and soft drinks. These foods are extensively marketed, relatively low in price, and readily available in vending machines and convenience stores.

"Massive efforts by food manufacturers and restaurant chains to encourage people to buy their brands must play a role. Promotions, pricing, packaging, and availability all encourage Americans to eat more food, not less" (Public Health Reports, 2000). "The food industry spends about $11 billion annually on advertising and another $22 billion on trade shows, supermarket 'slotting fees,' incentives, and other consumer promotions" (Gallo, 1996). In 1998, promotion costs for popular candy bars ranged from $10 million to $50 million, for soft drinks up to $115.5 million, and for the McDonald's restaurant chain just over a billion dollars. These figures dwarf the National Cancer Institute's $1 million annual investment in the educational component of its 5-a-Day campaign to increase consumption of fruits and vegetables, and the $1.5 million budget of the National Heart, Lung, and Blood Institute's National Cholesterol Educational Campaign (Cleeman & Lenfant, 1998). American children are bombarded daily with dozens of television commercials promoting fast food, snack food, and soft drinks (Public Health Reports, 2000). These advertisements are even commonplace in schools, thanks to Channel One — a private venture that provides free video equipment and a daily television "news" program in exchange for mandatory student viewing of commercials, along with school district contracts for exclusive soft drink marketing in vending machines and sports facilities (Public Health Report, 2000). "Advertising directly affects the food choices of children, who now have far more disposable income than they had several decades ago and far greater influence on their parents' buying habits" (Putnam, 1999).

These problems are compounded among residents of low-income neighborhoods, where there are often few grocery store options and limited access to fresh fruits and vegetables. Among the options that do exist, foods high in fat and sugar tend to be relatively inexpensive compared to healthier choices (Grantmakers in Health, 2001). The National Longitudinal Survey of Youth (2000) documents that the overweight prevalence among low-income African-Americans and Hispanics was 27.4%, while the prevalence among high-income whites was only 8%. According to Strauss and Pollack (2001), "the prevalence of obesity decreases as educational level increases. Among adults who have not completed high school, 26% are obese. For those who have completed college, the obesity rate is 15%."