William T. O’Donohue, Lorraine T. Benuto and Lauren Woodward Tolle (eds.)Handbook of Adolescent Health Psychology201310.1007/978-1-4614-6633-8_38© Springer Science+Business Media New York 2013
Obesity in Adolescence
(1)
University of Miami Miller School of Medicine, 1601 Northwest 12th Avenue, Miami, FL 33136, USA
Abstract
This chapter reviews research addressing obesity during adolescence. Epidemiologic findings indicate that obesity has increased dramatically in adolescents during the past several decades so that currently approximately one-third of adolescents in the United States are overweight, with about 17 % considered obese. Rates of obesity are greater among youth from ethnic minority and lower-income families. Overweight adolescents have a high likelihood of remaining overweight as adults. Etiologic factors indicate the important role of hereditary, early growth, and environmental factors, with behavioral factors of excessive caloric intake and decreased energy expenditure resulting in positive energy balance and increased adiposity over time. Review of the correlates of obesity reveals that adolescents have increased risk for several physical health disorders, including high blood pressure, high cholesterol, metabolic syndrome, type 2 diabetes, orthopedic problems, sleep apnea, asthma, and fatty liver disease. Psychosocial correlates of obesity in adolescents include increased risk for problems related to body image problems, self-esteem, social isolation and discrimination, depression, and reduced quality of life. Research on interventions for obesity in adolescents reveals the challenges of weight control over time; however there is some support for the efficacy of behavioral interventions targeting reduced caloric intake, increased physical activity, and reduced sedentary behavior. Medical interventions including pharmacological and surgical approaches have shown some efficacy, but more research is needed to demonstrate their safety and acceptability, as well as long-term effects. In recent years, Internet-delivered behavioral interventions have shown some promise and these approaches will likely be needed in order to more effectively reach the population of overweight adolescents. Given the tremendous challenge in successfully treating obesity during adolescence, and the costs of its continuation into adulthood, a public health approach is needed to address the environmental factors that are responsible for the increased incidence of obesity in youth.
Obesity has increased dramatically in American youth over the past several decades. Given the fact that obesity increases health risks, decreases quality of life, and is a chronic condition and difficult to treat, it constitutes a significant public health issue. The objective of this chapter is to review research concerning the epidemiology and prognosis of obesity in adolescents, etiologic factors, as well as physical health and psychosocial correlates, and approaches to intervention.
Epidemiology and Prognosis
Being overweight is defined as being heavier than is healthy given a person’s height. This includes having more body fat than is desired. Typically being classified as an overweight adult consists of having a body mass index (BMI) between 25 and 29.9. An adult is considered obese once his/her BMI is 30 or higher. BMI is calculated by taking a person’s weight in kilograms and dividing it by the square of the person’s height in meters (CDC, 2009a). A similar calculation is computed to determine a child’s BMI; however, gender and age are also added into the equation to account for differences in expected body fat at different developmental levels according to gender. A child or adolescent’s BMI which is at or above the 95 percentile compared to same aged and gender peers is considered obese (CDC, 2011); a BMI between the 85th and 95th percentile would be considered in the overweight range.
Although BMI is a generally accepted measure for obesity, it is not diagnostic since it is not a direct measure of body fat. Other measures of body fat distribution include skinfold thickness tests, waist circumference, calculation of waist-to-hip circumference ratios, ultrasound, computed tomography, and magnetic resonance imaging (MRI; CDC, 2009a).
Data from the United States National Health and Nutrition Examination Survey (NHANES) from 2007 to 2008 indicated that 17 % of children aged 2–19 years old met criteria for being obese according to BMI (Ogden, Carroll, Curtin, Lamb, & Flegal, 2010). For the 12–19-year-old group, the overall rate of obesity across ethnic groups and gender was 18 %, with 12 % of the sample having a BMI at or above the 97th percentile. When adolescents were divided into ethnic groups, the data indicated that 24 % of non-Hispanic Black adolescents, 22 % of Hispanic adolescents, and 16 % of non-Hispanic Caucasians met criteria for obesity according to BMI. Using logistic regression models, significant differences in the prevalence of obesity among ethnic groups were evident for adolescents. Specifically, Hispanic males had significantly higher odds of having a high BMI compared with non-Hispanic Caucasian males, and non-Hispanic Black females were significantly more likely than non-Hispanic Caucasian females to have a high BMI.
In addition to the data available from NHANES, there is another national study focused specifically on adolescents and their weight trajectories over time. The US National Longitudinal Study of Adolescent Health began in 1994 and initially recruited over 20,000 adolescents across the country in order to follow this nationally representative cohort into adulthood. Recent reports from this study indicate that obesity prevalence doubled from adolescent years to when the sample entered their early 1920s and then doubled again by the time the sample was in their late 1920s to early 1930s (Gordon-Larsen, The, & Adair, 2010). By 2008, obesity prevalence increased to 36.1 %, and was highest among non-Hispanic Black females. Obesity in adolescence has been associated with continued obesity in young adulthood, especially for non-Hispanic Black females, while across all ethnic and racial groups and for both men and women, only 5 % of normal-weight adolescents become severely obese (BMI > 40) in adulthood (The, Suchindran, North, Popkin, & Gordon-Larsen, 2010).
Etiologic Factors
Being obese is generally thought to be the result of a chronic caloric imbalance, with more calories being consumed than expended each day. History of obesity, hereditary factors, environment, metabolism, behavior, culture, and socioeconomic status all play a role in obesity.
Hereditary Factors and Early Growth
Most obese adolescents were overweight and/or obese as children. In fact, the origins of obesity are being traced to early childhood development. Adiposity rebound is a relatively new construct studied in the pediatric obesity literature. This refers to the time at which young children’s BMI begins to increase after a nadir. Children who experience early adiposity rebound (before the age of 5 years) have increases in mean BMI from age three to adolescence while those that experience late adiposity rebound have decreases in BMI from age three to adolescence. Early rebound has also been associated with increased depositions of fat in middle childhood. Data indicate that these differences are maintained into adulthood (Rolland-Cachera, Deheeger, Maillot, & Bellisle, 2006; Williams & Goulding, 2009).
There is also evidence to support a genetic component to obesity. For example, Whitaker, Wright, Pepe, Seidel, and Dietz (1997) found that parental obesity significantly increased the risk of obesity in adulthood for both children that were obese and those who were not, especially when children were under the age of 10 years old. Among those who were obese during childhood, 79 % in the 10–14-year-old group had at least one parent who met criteria for obesity.
Although some of the increased risk for obesity may be attributed to genetics, it is difficult to distinguish the genetic from the environmental component. Historically, high drives for storing fat were followed by periods of stress or high energy use resulting in decreases in body fat. Babies became thinner once they started growing and walking. However, the current environment consists of an excessive availability of high-fat and energy-dense foods combined with an increase in sedentary activities. This combination results in a disconnect between our biology and environment. While there is some inconsistency in the literature, there is evidence to support that both under- and overnutrition while a child is in utero can be related to obesity development (Adair, 2008).
Environmental Factors
The significant rise of obesity rates, specifically within adolescents, may be attributed to several multidimensional environmental changes that have impacted adolescents’ perceptions and value of nutritional intake, physical activity, and cognitions about maintaining a healthy lifestyle. While research has implicated the role of genetics and metabolism (Allison, Matz, Pietrobelli, Zannolli, & Faith, 1999; Meyer & Stunkard, 1993) in determining adolescents’ weight, the significant rise in adolescent obesity suggests that environmental factors (e.g., changes in nutrition, physical activity, and family environmental factors) are influential.
Dietary Factors
One important environmental factor is the current degree and type of food available to adolescents. Changes in dietary intake among adolescents have been linked to higher daily total energy intake. The consumption of food and beverages with higher levels of fat and sugar has increased substantially (Kantor, 1999; Putnam & Gerrior, 1999; Tippett & Cleveland, 1999). For example, data from the 2007 Youth Risk Behavior Survey indicated that in the past week 79 % of high school students had not eaten fruits and vegetables five or more times per day and 34 % had consumed soda at least one time per day (Eaton et al., 2008). Similar findings regarding factors related to fatty food consumption across countries have been documented (Gerrits et al., 2010), with self-control, concern about diet, and unhealthy eater prototype being related to the amount of fatty foods consumed.
Adolescents’ access and frequency of visits to fast-food restaurants, where food is higher in fat and energy relative to food served at home, has increased substantially with over 30 % of youth eating at least one fast-food meal a day and 75 % reporting eating fast food at least once a week (Bowman, Gortmaker, Ebbeling, Pereira, & Ludwig, 2004; French, Story, Neumark-Sztainer, Faulkerson, & Hannan, 2001; Lin, Guthrie, & Blaylock, 1996; Lin, Guthrie, & Frazao, 1999a, 1999b). Further, the frequency of fast-food restaurant use by adolescents has been linked to increased intake of total calories, percent of calories from fat, daily servings of soft drinks, cheeseburgers, french fries, and pizza. An inverse relationship between fast-food restaurant usage and daily servings of fruit, vegetables, and milk has also been documented (French, Story, Neumark-Sztainer, Faulkerson, & Hannan, 2001). In addition to nutritional associations, fast-food restaurant use has also been associated with other behaviors including increased rates of student employment, more time spent watching television, greater availability of “junk food” in the home, and more perceived barriers to healthy eating (French et al., 2001).
Not all unhealthy eating habits can be attributed to the fast-food industry. Even at school, adolescents are frequently limited to school lunches consisting of high calorie foods such as pizza or hamburgers (Miller, Gold, & Silverstein, 2003). In addition, school-wide food practices such as allowing students to have food in the classroom and hallways and using food as a reward are linked to increased BMI in middle school students (Kubik, Lytle, & Story, 2005). Further, the cost of healthy food relative to foods with higher fat and sugar content appears to affect adolescents’ food choice. That is, there is some support to suggest that reducing the price of fruit and vegetables within high schools results in a substantial increase in fresh fruit and vegetable sales (French, 2003). There is even evidence to support that adolescents would prefer to have healthier options offered at school. Goslinger, Madsen, Woodward-Lopez, and Crawford (2011) conducted a study with a sample of over 5,000 youth in low-income areas across California which found that most students reported that it was important to have access to purchase fruit at school, more so than they valued the availability of chips, candy, or soda. Although students report wanting healthier choices, there is also evidence to support that the actual behavior of students may differ depending on the availability of unhealthy foods and snacks at school. For example, nearly 20 % of middle school students reported buying snacks from a vending machine at least 2 out of 5 days in the past school week instead of purchasing school lunch (Parks, Sappenfield, Huang, Sherry, & Bensyl, 2010). In general, the choices available from school vending machines include sodas and calorie-dense snacks. Therefore, many researchers and obesity activists promote making environmental changes, especially in the school setting, to assist students in making better nutritional choices.
Physical Activity
In addition to caloric intake, lack of energy expenditure (typically as a result of physical activity) is also a major contributor to adolescent obesity. Sallis, Prochaska, and Taylor (2000) conducted a comprehensive review of the literature on variables that are potentially related to physical activity in youth. Results indicated that adolescents who were males, white, and younger; perceived themselves as competent athletically; previously engaged in physical activity; had support from parents and others; and had opportunities to exercise were more likely to engage in physical activity than those who did not have these attributes.
Several studies have shown that physical activity levels decrease significantly from childhood to adolescence (Heath, Pratt, Warren, & Kann, 1994), particularly among black girls (Kimm et al., 2002). While it is generally believed that the current generation of adolescents is far less active than past generations, an examination of physical activity of high school students between 1993 and 2003 using the Youth Risk Behavior Survey (YRBS) demonstrated that while there were statistically significant decreases in physical activity by high school boys and adolescents in grades nine and ten, decreases over time were generally small (Adams, 2006). That is, children decrease physical activity as they enter adolescence, but the overall trend in decreased physical activity among adolescents from 1993 to 2003 was minimal. However, results from the 2007 national YRBS indicated that among high school students nationwide, 35 % had watched television 3 or more hours per day on an average school day during the past month and 65 % had not met recommended levels of physical activity during the past week (Eaton et al., 2008). Specific traits associated with declines in physical activity in adolescence have been examined. For example, higher perceived behavioral control, support for physical activity, and self-efficacy have been associated with smaller declines in physical activity in a review of the available literature on longitudinal patterns of physical activity in adolescents (Craggs, Corder, Van Sluijs, & Griffin, 2011).
Adolescents’ access to physical activity facilities (e.g., parks, public facilities, YMCAs, and schools) within their neighborhood is related to their engagement in exercise and risk of being overweight (Gordon-Larsen, Nelson, Page, & Popkin, 2006). That is, the risk of being an overweight adolescent decreases with increasing number of physical activity facilities available to adolescents within their neighborhood. However, adolescents who live in neighborhoods with a high proportion of ethnic minorities and those with a lower education are at a higher risk for lack of physical activity facilities.
Family Factors
It also appears that the family environment impacts adolescent overweight. Family influence on eating habits begins at a young age and continues into adulthood. One important factor in influencing young children’s energy intake is maternal behavior or style related to children’s eating. There is substantial research documenting the significant role of maternal behavior in affecting young children’s eating behavior. For example, research shows that stringent parental controls over children’s food intake can result in preferences for high-fat, energy-dense foods; negatively affect the variety of food children are willing to eat; and alter children’s responsiveness to internal cues of hunger and satiety (Birch & Fisher, 1998). Modeling of eating behaviors is another way parents influence childhood obesity. Breakfast consumption in adolescents (which has been identified as having multiple health benefits) has been associated with parental breakfast eating and living in two-parent families (Pearson, Biddle, & Gorely, 2009). In addition to parental modeling of positive eating habits, other aspects of parent involvement have been found to positively influence physical activity in adolescents. Family cohesion, effective parent-child communication and parental engagement have been found to positively predict bouts of moderate to vigorous physical activity per week in both adolescent males and females (Ornelas, Perreira, & Ayala, 2007).
There are also various negative parental influences on obesity rates that have been identified in the literature. Even after controlling for sociodemographic variables, adolescents with an overweight mother or father were at an increased likelihood of being overweight or obese as a young adult based on the US National Longitudinal Study of Adolescent Health (Crossman, Sullivan, & Benin, 2006). Lower parental education and a weaker perception that parents care during adolescence were related to a higher risk for being overweight as an adult female, whereas being African American or Native American reduced the risk for being overweight (Crossman, Sullivan, & Benin, 2006). Adolescent males were at increased risk for becoming overweight as adults when they perceived a close relationship with their parents and when their parents were viewed as trying to control their eating behaviors. Further, the amount of television viewing within the home by adolescents was positively related to an increased BMI in young adulthood (Hancox, Milne, & Poulton, 2004).
Health and Psychological Correlates of Obesity in Adolescence
With increasing rates of obesity among youth populations, it is also important to consider the physical health and psychological correlates and consequences of this condition. The consequences of childhood and adolescent obesity are far reaching, not only including health-related physical outcomes but also psychological, social, and behavioral consequences. The consequences of being overweight may be severe, including higher risk for cardiovascular diseases, type 2 diabetes, cancer, hypertension, dyslipidemia, stroke, orthopedic problems, and sleep apnea (CDC, 2009b). In addition to health consequences, there are also significant psychological and psychosocial consequences of being overweight, including psychological distress, discrimination, and medical treatment expenses for various health problems.
Health Correlates
With increasing rates of obesity among youth, it is important to consider the potential adverse health effects of this condition. The toll of obesity on adolescents’ health is well documented. Today adolescents exhibit a higher frequency of health difficulties that were once only seen in adults. Such conditions include high blood pressure, type 2 diabetes, metabolic syndrome, polycystic ovary disease, fatty liver disease, sleep apnea, and orthopedic complications (Daniels, 2006; Dietz, 1998; Reilly, 2005).
Reilly et al. (2003) compiled empirical data which described the health consequences of obesity in youth. Among these health problems were associations between obesity (as measured by BMI and central obesity/waist circumference) and cardiovascular risk factors such as high blood pressure, dyslipidemia, abnormal left ventricular mass, and insulin resistance. The prevalence of cardiovascular risk factors among obese youth is high and has been estimated at 58 % with one risk factor and 25 % with two or more (Freedman, Dietz, Srinivasan, & Berenson, 1999).
Related to increased cardiovascular risk is the risk for metabolic syndrome among obese children and adolescents. This condition refers to the clustering of metabolic and cardiovascular risk factors (i.e., large waist circumference, high triglycerides, low levels of HDL cholesterol, high blood pressure, and high fasting blood glucose or insulin resistance) and is associated with increased risk for type 2 diabetes. Estimates of the prevalence of metabolic syndrome among obese youth range from 6.8 to 28.7 %, though it is speculated that these may underestimate the true extent of the problem (Cook, Weitzman, Auinger, Nguyen, & Dietz, 2003; Weiss et al., 2004). Weiss et al. (2004) found that the prevalence of metabolic syndrome increased with the severity of obesity, reaching as much as 50 % in extremely obese children. Nathan and Moran (2008) recently estimated that half of obese adolescents have metabolic syndrome.
Asthma also represents a common and prevalent complication associated with obesity in youth. Previously, researchers were unclear about the association between asthma and obesity, but recent studies illustrate a significant relationship between these conditions (Gennuso, Epstein, Paluch, & Cerny, 1998; Reilly, 2005). Visness et al. (2010) reported results on the relationship between asthma and obesity based on data collected in a 7-year NHANES. Results of the survey, which reflected data on 16,000 children and adolescents, showed significant relationships between obesity and a diagnosis of asthma, with non-atopic asthma showing a greater correlation. This relationship was previously demonstrated in a study of 300 Israeli youth, where obesity was associated with more wheezing, more frequent physician-diagnosed asthma, and more prevalent inhaler use than in non-obese youth (Bibi et al., 2004).
The long-term health consequences of obesity in youth are also important to consider. Several researchers have reported the long-term continuation of cardiovascular risk from childhood into adulthood (Freedman et al., 1999; Reilly, 2005) and have cited a significant relationship between obesity in adolescence with premature mortality (Daniels, 2006; Must, Jacques, Dallal, Bajema, & Dietz, 1992). Such studies are difficult to conduct given their longitudinal design; however, there is evidence to support the lifetime trajectory of obesity and related health complications.
Psychological and Psychosocial Correlates
In addition to the health consequences of obesity, psychological and psychosocial functioning are also areas of concern for obese adolescents. Body image difficulties represent one area where obese adolescents may struggle with psychological challenges. Researchers have noted adolescence as a time of particular vulnerability to body image concerns (Wardle & Cooke, 2005). There is an established relationship between weight issues and body dissatisfaction, most notably in girls (Davidson & Birch, 2002; Davidson, Markey, & Birch, 2003; Ricciardelli & McCabe, 2001). Among adolescent boys, findings show body dissatisfaction among overweight as well as underweight boys (Presnell, Bearman, & Stice, 2004). These findings suggest that body dissatisfaction is certainly a prevalent concern among obese adolescents; however, it is not a concern that is specific only to the overweight adolescent population.
Obese and overweight adolescents exhibit psychological difficulties beyond those related to dissatisfaction with body image. The effects may extend into other parts of their lives such as perceptions of competence with physical activity, school, as well as in social settings. For example, obese girls are more likely to be victims of bullying, while obese boys are more likely to be victims of bullying as well as perpetrators of bullying (Griffiths, Wolke, Page & Horwood, 2006). The social effects of obesity were described in an investigation of the relationship between overweight and social marginalization (Strauss & Pollack, 2003). Results showed that overweight adolescents were rated as less popular than their normal-weight peers and were less likely to be selected as friends by their peers, a social stigmatization trend that has also been shown among preschool-aged children (Musher-Eizenman, Holub, Barnhart Miller, Goldstein, & Edwards-Leeper, 2004). Overweight adolescents have been described as being “more isolated and more peripheral to social networks” and reported to have lower rates of best friend reciprocity (Strauss, Smith, Frame, & Forehand, 1985).
The social correlates of obesity may be largely explained by the societal stigma related to obesity that is well documented in the literature. Obese individuals are frequently stereotyped as ugly, mean, stupid, and lazy (Faulkner et al., 2001; Latner & Stunkard, 2003; Wardle, Volz, & Golding, 1995). Similar descriptions have been given in studies with young children presented with pictures of children of varying physical characteristics. Young children consistently rated overweight children as least liked and least likely to be a playmate (Richardson, 1971). Given the association between adolescent friendships and self-esteem, it is hypothesized that social marginalization contributes to reduced self-esteem and increased rates of depression among overweight teens (Caskey & Felker, 1971; Strauss et al., 1985).
Of the many psychological consequences of obesity, the prevalence of depression among overweight and obese adolescents is a topic of considerable debate. Some studies found no association between depressive symptoms and BMI (e.g., Friedman & Brownell, 1995; Vila et al., 2004). Stice and Bearman (2001) found that higher body mass in adolescent girls did not predict depression 20 months and 4 years after enrollment. Similar results were described by Goodman and Whitaker (2002), showing no association between obesity at the time of enrollment and depression at a 1-year follow-up visit.
However, other researchers have found a significant relationship between obesity and depression among teens. In a study of Chinese adolescents, Xie et al. (2005) reported a significant relationship between high BMI and higher self-reported depressive symptoms among girls, mediated by perceived peer isolation. When compared to normal-weight peers, obese adolescents had significantly more depressive symptoms, and this difference persisted when comparing obese adolescents to those who were in the overweight range (Sjoberg, Nilsson, & Leppert, 2005). In a study by Stice, Hayward, Cameron, Killen, and Barr (2000), body dissatisfaction and dietary restraint were shown to be significant risk factors for depression among adolescent girls and in a study of seventh, ninth, and eleventh graders, Faulkner et al. (2001) found more and stronger associations for obese adolescent girls than for obese boys. These associations included greater likelihood of social isolation, feelings of hopelessness, as well as greater likelihood for past suicide attempts. Together these results indicate an inconsistent relationship between obesity and depression in adolescents.
In addition to the psychological and psychosocial consequences of obesity, there has also been research addressing the prevalence of psychiatric disorders among obese adolescents. Lamertz, Jacobi, Yassouridis, Arnold, and Henkel (2002) investigated this issue in their community survey study of German youth ranging in age from 14 to 24 years. Results indicated no significant relationships between BMI and mental disorders or psychopathology (i.e., anxiety, substance abuse, mood disorders, somatoform disorders). In another community-based study, researchers found clinical diagnoses of anxiety and depression to be associated with higher weight status and higher BMI (Anderson, Cohen, Naumova, & Must, 2006), which they suggested may support anxiety and depression as precursors to obesity later in life. When the rates of psychopathology were investigated among a population of extremely obese adolescents (BMI > 40), significant differences emerged between the extremely obese group and the obese population-based controls, with the extremely obese teens having higher rates of mood, anxiety, somatoform, and eating disorders (Britz et al., 2000).
Overall, the research findings indicate that obese adolescents are at increased risk for psychological and psychosocial difficulties which are more likely the consequence of obesity rather than causal factors. Quality of life has been shown to be significantly lower in obese youth and at a level comparable to youth with cancer (Schwimmer, Burnwinkle, & Varni, 2003). A study conducted by Gortmaker, Must, Perrin, Sobol, and Dietz (1993) followed obese adolescents for 7 years. Results indicated that young obese women completed less years of school, had lower household incomes, experienced higher rates of poverty, and were less likely to be married than women who had not been obese. Obese men were less likely to be married. This study demonstrated the socioeconomic discrimination that many obese individuals may experience.
Obesity Interventions
Given the increasing rates and persistence of obesity in youth as well as the many adverse consequences, researchers have focused their efforts on developing interventions to treat obesity in adolescents and prevent its persistence into adulthood. Interventions have targeted increasing physical activity and improving dietary behavior through several approaches (Kamath et al., 2008), including schools, clinics, community-based programs, and eHealth programs delivered over the Internet or with mobile technology. Medical interventions including various medications and bariatric surgery have also been studied.
School-Based Interventions
Parents identify schools as having a great responsibility in reducing obesity in youth (Kropski, Keckley, & Jensen, 2008). Furthermore, recent trends in national legislation identify school-based intervention programs as preferable methods for reducing rates of obesity (Foster et al., 2008). Several approaches have been used in school-based obesity programs, including nutritional interventions (e.g., James, Thomas, Cavan, & Kerr, 2004), physical activity interventions (e.g., Sallis et al., 1993), and combinations of both intervention strategies (e.g., Coleman et al., 2005). The objective in these programs is generally preventive in focus, with an attempt to change behavioral patterns in all youth rather than selecting only overweight youth.
School-based health education programs have been somewhat successful in reducing dietary fat intake, increasing fruit and vegetable consumption, and increasing physical activity in children (Kelder, Perry, Lytle, & Klepp, 1994; Killen et al., 1988; Luepker et al., 1996; Perry et al., 1998; Sallis et al., 1997). These school-based programs have had several components, including a health education curriculum, as well as making changes in the school food service and physical education (PE) curriculum. Newer school-based programs have emphasized changing the school environment through social marketing approaches (Walsh, Rudd, Moeykens, & Maloney, 1993) so that health promotion attains a higher priority for children, teachers, school administrators, food service personnel, as well as parents.
In school-based obesity intervention programs focused on physical activity, researchers have geared programs toward increased duration of aerobic exercise during PE times (e.g., Sallis et al., 1993, 1997). The Eat Well and Keep Moving classroom-based intervention program focused on increasing fruit and vegetable consumption, limiting television viewing, and increasing physical activity (Lin et al., 1999a). The intervention was delivered by classroom teachers who integrated the intervention into their typical classroom curriculum. Similarly, Project SPARK included a physical activity curriculum whereby students participated in a “recommended schedule” of three 30-min classes per week, divided into three segments (i.e., warm up, cardiovascular, cool down/stretch) (Sallis et al., 1993, 1997).
Newer school-based health promotion programs have focused specifically on reducing obesity and several have been shown to be effective (Davis, Davis, Northington, Moll, & Kolar, 2002; Doak, Visscher, Renders, & Seideil, 2006). For example, Planet Health (Gortmaker et al., 1999) focused specifically on reducing obesity and added intervention components that targeted reducing time spent viewing television and playing video games. This intervention was successful at reducing obesity in girls, and decreasing television influenced the reduction in obesity. Another school-based study focused only on reducing television viewing and demonstrated a reduction in obesity (Robinson, 1999). The reduction of sedentary behavior is clearly an integral component of weight loss programs (Epstein et al., 1995) and has become a more prominent focus of treatment of obese youth in recent years (Leung, Agaronov, Grytsenko, & Yeh, 2011; Wahi, Parkin, Beyene, Uleryk, & Birken, 2011).
This focus on nutrition and physical activity is common among school-based intervention programs. Physical activity is often measured via minutes of participation in a PE classroom protocol. For example, participants in the Healthy Study Group diabetes risk reduction project participated in a minimum of 150 min of moderate to vigorous activity over 2 weeks during the required minimum of 225 min of PE class time (The Healthy Study Group, 2010). This multisite national study evaluated the effects of a comprehensive multicomponent school-based program to reduce obesity and risk of type 2 diabetes in 6th grade children followed until the end of 8th grade. Besides increasing physical activity, the program emphasized healthy nutrition, behavioral knowledge and skills, and communication strategies and social marketing to support the intervention. Results showed the intervention schools had greater reductions in BMI, prevalence of obesity, and fasting insulin (indicating reduced risk for type 2 diabetes).
Clinic-Based Interventions
Dietary Approaches
Several clinic-based studies have compared the effects of different dietary interventions with overweight adolescents, and preliminary findings suggest that type of nutritional intake may affect weight loss. In a 12-week randomized controlled trial comparing the effects of a low-carbohydrate diet with those of a low-fat diet on weight loss and serum lipids in overweight adolescents, those in the low-carbohydrate group displayed significantly greater reductions in their BMI and improvements in non-HDL cholesterol levels relative to adolescents in the low-fat group (Sondike, Copperman, & Jacobson, 2003). Adolescents in the low-fat group displayed improvements in LDL cholesterol level, but those in the low-carbohydrate group did not show these improvements. Less than half of treatment participants returned for a 1-year follow-up assessment, but none of them returned to their baseline BMI. In another trial with overweight adolescents comparing reduced carbohydrate and fat diets, the reduced carbohydrate treatment group displayed greater reductions in BMI and fat mass at 6- and 12-month follow-up (Ebbeling, Leidig, Sinclair, Hangen, & Ludwig, 2003).
Another approach to obesity intervention involves hospitalization or residential treatment to implement specific dietary interventions. One comparative study of dietary restrictions was conducted in a residential setting over 9 months. In this study, 121 extremely overweight adolescents were randomized into either an increased protein dietary intake or decreased carbohydrate intake group. Participants significantly reduced their weight, but there were no differences between dietary groups in weight loss (Rolland-Cachera et al., 2004). At 2-year follow-up, adolescents regained a significant portion of their weight due to increased energy intake (particularly snacking) and sedentary behaviors after returning home. However, it is important to note that recent research with obese adults indicates that reduced calorie diets result in weight loss regardless of which macronutrients are emphasized (Sacks et al., 2009).
Seventeen obese adolescents were admitted into a hospital for 1 month and then followed in an outpatient setting for a total of 12 months to implement a protein-sparing modified fast diet (a high-protein, low-calorie diet). Results indicated that nearly half displayed significant decreases in body weight after 1 year (Stallings, Archibald, Pencharz, Harrison, & Bell, 1988). In another report involving inpatient treatment, 122 obese youth participated in a 10-month comprehensive program with dietary restriction with a 14-month follow-up. Results from this non-randomized study indicated that these youth lost 49 % of their weight after 10 months, and at follow-up they maintained a 32 % weight loss; they also reported improved dietary habits and psychological well-being (Braet, Tanghe, Decaluwé, Moens, & Rosseel, 2004).
In another non-randomized study, 56 obese adolescents participated in a comprehensive 1-year outpatient program consisting of an acute phase with a very low-calorie diet (800 calories per day) followed by a less restrictive hypocaloric diet, moderate-intensity physical exercise, and behavior modification with parental involvement to reinforce behavioral changes (Sothern, Udall, Suskind, Vargas, & Blecker, 2000). Most youth (93 %) completed the acute phase with a mean weight loss of 9.4 kg; 63 % completed the 1-year program. The results at 1 year indicated that significant reductions in BMI occurred, particularly for the most obese adolescents. This study provides preliminary support for very low-calorie dietary approaches, but it is difficult to evaluate the unique effects of parent participation, exercise, and diet on treatment outcome. More controlled work using this approach is needed.
Multicomponent Family Approaches
Family-based behavioral interventions targeting both dietary intake and physical activity have been shown to be efficacious in overweight children, with significant weight loss maintained even 10 years after treatment (Epstein, Valoski, Wing, & McCurley, 1994, 1998), but fewer family-based studies have been conducted with overweight adolescents. In an early study of multicomponent family intervention, overweight adolescents (ages 13–17) were randomly assigned to either a mother and adolescent seen separately condition or adolescent seen alone condition (Coates, Killen, & Slinkard, 1982). Treatment included 14 weekly, 90-min group sessions, two-parent sessions, on-site exercise, and leader-facilitated interactions about weight control behaviors. At posttreatment, both treatment groups exhibited decreases in percentage overweight (8.6 % and 5.1 %, respectively, for adolescent-mother and adolescent alone). At 18-month follow-up, both groups continued to show decreases in percentage overweight from baseline (8.4 % adolescent-mother, 8.2 % child alone).
In a study with a predominately Caucasian sample of 12–16-year-old adolescents that were randomly assigned to three treatment formats (i.e., mothers and adolescents seen separately, mothers and adolescents seen together, adolescents seen alone), treatment type affected outcomes (Brownell, Kelman, & Stunkard, 1983). Treatment included 45–60-min group sessions for 1 year (16 weekly sessions then 1 session every 2 months) and participants were provided with nutrition and exercise education, rewards for attendance and weight loss, stimulus control, and behavior modification. At posttreatment, the mothers and adolescents that were seen separately displayed better outcomes (17.1 % decrease in percent overweight) than when mothers and adolescents were seen together (7.0 % decrease in percent overweight) or when adolescents were seen alone (6.8 % decrease in percent overweight). However, a study that sought to replicate these findings in a predominately African American adolescent sample was unsuccessful (Wadden et al., 1990). That is, treating the adolescent and the mother separately did not have a differential impact on treatment outcomes, although weight loss was positively correlated to the number of sessions attended by the parent.
In a randomized controlled trial of a family-based intervention conducted in Israel, 46 6–16-year-old overweight youth were randomly assigned to a multicomponent 3-month treatment group or a control group (Nemet et al., 2005). Youth were first invited to a session with their parents and a dietitian, and then youth meetings alternated with parent meetings, for a total of six meetings in the 3-month program. Participants followed a balanced hypocaloric diet, with a deficit of 30 % from reported intake or intake 15 % less than daily required intake, and also participated in an hour-long physical training program twice weekly; they were also encouraged to complete 30–45 min of walking or weight-bearing sport activities at least once per week. At posttreatment, youths in the multicomponent intervention group achieved significant reductions in body weight, BMI, and body fat percentage and significant increases in physical activity compared to participants in the control group. Long-term effects were positive with maintenance of body weight and a reduction in BMI and body fat percentages of the intervention group.
One promising intervention for adolescent obesity is the ShapeDown program (Mellin, Slunkard, & Irwin, 1987). In this non-randomized study, adolescents (ages 12–18) attended 14 weekly, 90-min group sessions. Sessions included nutrition education, on-site exercise, two parent sessions, and discussions about weight control behaviors. At posttreatment, adolescents who participated in the program demonstrated a significant decrease in their percentage overweight (5.9 %) and at a 15-month follow-up, program participants displayed further decreases in the percentage overweight (9.9 %).
A randomized controlled trial was conducted to evaluate the effects of an exercise program on BMI and psychological outcomes in 81 overweight adolescents (Daley, Copeland, Wright, Roalfe, & Wales, 2006). Overweight youth (ages 11–16 years) were randomly assigned to receive exercise therapy, an equal contact exercise placebo, or usual care. The exercise therapy group engaged in aerobic exercise activities for 30 min three times weekly for eight weeks (24 sessions). During the first 12 sessions, participants were also introduced to cognitive-behavioral strategies consistent with the transtheoretical model. During the last 12 sessions, behavioral interventions including goal setting, self-monitoring, and increasing social support were utilized. The results did not show significant reductions in BMI; however, the exercise therapy group and exercise contact group displayed significant improvements in physical self-worth compared to the usual care group which persisted 14- and 28-week follow-ups.
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