Prevalence

Using BMI ≥ 95^th percentile, the prevalence of overweight in 1999-2002 was 10% in two- to five-year-olds and 16% in those six years and older⁷⁷ (Figure 3). For children two to five years of age, the prevalence was similar between all racial/ethnic subgroups and both sexes, but was lower than the prevalence in older children in the same racial/ethnic subgroups. Among children 6 to 11 years, differences were seen between racial/ethnic subgroups, with significantly more Mexican American (21.8%) and non-Hispanic black (19.8%) children categorized as overweight, compared with non-Hispanic whites (13.5%) (p<.05). Sex-specific differences were also seen, with the highest prevalence of overweight in 6- to 11-year-olds among Mexican American boys (26.5%), which was significantly higher than non-Hispanic black boys (17%), non-Hispanic white boys (14%), and Mexican American girls (17.1%), and similar to that of non-Hispanic black girls (22.8%). Among youth aged 12 to 19 years, significantly more non-Hispanic black (21.1%) and Mexican American (22.5%) children had overweight BMI measurements than non-Hispanic whites (13.7%) (p<.05), with no differences between males and females.

Figure

Prevalence of Overweight 1999-2002 % with BMI equal to or greater than 95%with standard error bars. Prevalence of Overweight or at Risk for Overweight 1999-2002 % with BMI equal to or greater than 85% with standard error bars. (more...)

NHANES does not provide separate estimates for Native American children. In a population-based survey of 12,559 schoolchildren aged 5 to 17 years representing 18 tribes in the Midwest in 1995-1996, the overall age-adjusted prevalence of overweight was significantly greater in males (22.0%, 95% CI 21.0–23.0) than in females (18.0%, 95% CI 17.0–19.0).⁷⁸ In five-year-olds, the overweight prevalence was not significantly different in boys (16.1%) and girls (11.6%). Between ages 6 and 11 years, overweight prevalence remained similar between sexes, ranging from 12.0% to 24.6% in boys and 15.0% to 20.7% in girls. Beginning at age 12, males had consistently higher prevalence of overweight (20.9% to 25.9%) than females (15.9% to 22.5%).

Given the differences in reporting, it is difficult to directly compare prevalence estimates for Native Americans to other races/ethnicities. However, the overweight prevalence of Native American boys aged 6 to 11 is between that of non-Hispanic blacks (the second-highest prevalence) and the most prevalent group, Mexican Americans. Similarly, for girls 6 to 11, the prevalence of Native American overweight appears to rank between the second-highest (Mexican Americans) and the highest groups (non-Hispanic blacks). In adolescents, a similar ranking is seen in boys and girls, despite the younger age representation of Native American children (12 to 17 years) compared with other races (12 to 19 years). Thus, it appears that Native American children aged 6 to 17 rank as at least the second-highest group in prevalence of overweight among races.

The prevalence of overweight based on BMI changed little between 1960 and 1980 among children and adolescents in the United States.¹ Using the same reference population, sex- and age-specific subgroups aged 2–19 years showed an increase in overweight prevalence between the 1988-1994 and 1999-2000 surveys, which was similar to, or greater than, increases during the longer time period between earlier surveys (NHANES II [1976-1980] and NHANES III [1988-1994]).⁷⁵ In the 6–12 years before 2000, statistically significant increases in the prevalence of BMI measures above the 95^th percentile threshold for overweight occurred among all 2- to 5-year-olds (3.1%), all 6- to 11-year-olds (4.0%), and all 12- to 19-year-olds (5.0%), with 12- to 19-year-old boys increasing 4.2% and girls increasing 5.8% (p<.05). When analyzed by race/ethnicity, only non-Hispanic black and Mexican American children exhibited statistically significant increases in prevalence between 1988 and 2000. In Mexican Americans, the prevalence increased 13% in boys, and the prevalence increased 10% in both non-Hispanic black boys and girls in. Among all 12- to 19-year-olds, 11.2% met the adult definition of obesity (BMI of 30 or higher), with rates particularly high among non-Hispanic black females (20%) and Mexican American females (16%). Other data also demonstrate increased severity of excess weight among overweight children,⁷⁹ especially black and Mexican American children,¹² increasing the sense of urgency about childhood overweight.⁸⁰

Important caveats apply to estimating the prevalence of overweight prevalence and trends among groups other than non-Hispanic whites. Unfortunately, representative national data are unavailable to reliably estimate the prevalence of overweight in children and adolescents of Asian/Pacific Islander descent. While recent surveys such as NHANES 1999-2000 have over-sampled Mexican Americans and non-Hispanic blacks,⁷⁵ comparable race/ethnicity information for these groups is limited to NHANES III and NHANES 1999-2000, with some supplementation by Hispanic HANES (1982-1984) (Appendix R). Commonly used growth references, such as the CDC's sex-specific BMI-for-age charts, which are based primarily on white and black samples from 1963 through 1980 (through 1994 for those under age 6),⁶¹ may inaccurately measure the prevalence of overweight in Mexican American youth⁵⁴or in Native Americans. Similarly, blacks are represented but do not make up the majority, and metabolic consequences in blacks, whites, and Hispanics at the same BMI z-score have been shown to differ.³⁰ These same issues could pertain to applying the available growth references to Native Americans. Given the known differences in body composition and growth and development between races,^{47, 57, 81, 82} and possible differences in the validity of BMI as a proxy for percent body fat in different races,⁵⁰ it will be important to clarify the health significance of BMI measurements at various ages among boys and girls of racial/ethnic subgroups.⁴⁹

Behavioral Counseling Interventions

The most extensive treatment literature for childhood overweight involves behavioral counseling interventions. Behavioral counseling interventions are those activities delivered by primary care clinicians and related healthcare staff to assist patients in adopting, changing, or maintaining health behaviors proven to affect health outcomes and health status.⁹³ These interventions may occur, all or in part, during routine primary care and may involve both visit-based and outside intervention components, including referral to more intensive clinics in the community. Behavioral counseling interventions reviewed here included behavioral modification special diets, and/or activity components delivered to children and/or parents as individual or in groups.

We considered all trials published since 1985 (n = 22 from 23 publications) that addressed interventions that were feasible for primary care conduct or for primary care referral (including one that combined comprehensive behavioral treatment with pharmacotherapy, described separately below).⁹⁴–¹¹⁶We limited our consideration to post-1985 trials given the dramatic increases in overweight in children that have occurred during the 1980s and 1990s.^{5, 11, 80} A previous good-quality systematic review covering 16 of these trials concluded that this behavioral counseling treatment literature is limited, due to small sample sizes and marginal-quality trials testing primarily non-comparable interventions delivered in specialty obesity clinic treatment settings to significantly overweight school-aged children (40%–50% above ideal weight) with primarily short-term outcomes.⁷² We found limited improvement from these conclusions by including six additional studies published in the interim (Table 5). These studies continued to be very small (16 to 82 participants), to primarily analyze treatment completers only, and to examine very different interventions over a relatively short period of time. Studies also tended to target those who were quite overweight (see Figure 4). Inclusion criteria and weight outcome measures tended to be BMI-related more than the earlier literature, likely reflecting the growing consensus about the use of BMI.

Table 5

Randomized Controlled Trials Addressing Overweight in Children and Adolescents.

Figure

Figure 4. Effects of behavioral weight loss treatment on BMI for children ages 8 to 13: Modeled results using CDC Growth Charts: United States. Body mass index-for-age percentiles: Girls, 2 to 20 years.

Over half (n=13) of fair- or good-quality trials^{94, 96}–^{102, 105, 107, 112, 113, 116} reported intermediate behavioral (n=11) or physiologic (n=7) measures in addition to weight outcomes (Table 5). These outcomes were more common in recent research, and five of the six recent studies reported one or more. Two good-quality trials^{113, 116} reported behavioral changes but no physiological outcomes. While one of these trails¹¹⁶ indicated reduced total daily energy intake in the active treatment group, neither indicated changes in physical activity. One fair-quality study reported reductions in targeted dietary components (fat or glycemic load of diet), but not kilocalories,⁹⁶ while other fair-quality studies⁹⁷–^{102, 107, 112} measuring changes in eating behaviors, physical activity, and sedentary behaviors did not provide a clear picture due to differences in subjects, interventions, and measures. No good-quality trials of behavioral treatment without pharmacologic adjuncts reported intermediate physiologic outcomes, such as lipids or lipoproteins, glucose tolerance, blood pressure, or physical fitness measures. Only one trial of at least fair quality reported key intermediate physiologic measures such as lipids or lipoproteins, glucose tolerance, or blood pressure. After an intensive six-month behavioral weight-control program comparing a reduced glycemic load (RGL) diet with a reduced fat (RF) diet, insulin resistance scores (measured by the homeostatic model) increased significantly less in the RGL group than the RF group (-0.4 +/- 0.9 vs. 2.6 +/- 1.2, p=0.03).⁹⁶ Insulin resistance, however, increases with sexual maturation, which was not assessed. The significance of these results is further limited given baseline differences between groups and lack of consideration of physical activity as a confounder. The other fair-quality studies measured other physiological outcomes such as physical work capacity or physical fitness and most reported some improvement when physical activity or sedentary behaviors were addressed in the intervention.^{97, 98, 101, 102}

Considering all trials covered in the earlier review and this one (Table 5), no current trials addressed preschool children (two to five years of age). The majority of trials addressed children aged 6 to 12or 13 years (n = 15), with a growing number of studies addressing adolescents aged 11 or 12 years and older (n = 7). Studies generally include boys and girls, with some over-representation of females. Few studies clearly included 10% or more non-whites (n = 7), and many did not report participants' race/ethnicity (n = 12). Two studies included 100% black female adolescents,^{115, 116} but only one met at least fair quality criteria.¹¹⁶

Comprehensive behavioral treatment programs have been the most studied intervention for overweight (Table 5). Fair- or good-quality studies have produced from 7% to 26% (generally 10%–20%) decreases in percent overweight (the most commonly reported outcome) from baseline after 12 to 24 months of intensive treatment. Much of this research has come from a single research group treating select patients aged 8–12 in a multidisciplinary obesity clinic setting specializing in behavioral therapy approaches to changing diet and activity behaviors.⁷⁰ Figure 4 models the BMI impacts of a 10%–20% reduction in overweight after 12 months in girls enrolled at ages 8–12. Methods for these calculations are described in Appendix P.

Long-term (after 5 to 10 years) weight outcomes from a set of these studies in 8–12 year olds in a multidisciplinary obesity clinic setting¹¹⁷ generally maintained or improved weight-related treatment measures for the majority of patients. These studies are often cited,^{118, 119} but we excluded them from our review because most were prior to 1985, all involved intensive treatment-to-treatment comparisons without untreated controls, and we could not confirm the long-term results met our quality criteria (acceptable loss to follow-up of all those randomized, since analyses were not intention to treat).⁶⁸ Although this evidence offers hope of some success in treating childhood overweight for some subgroup of those treated, more generalizable and reliable evidence will be needed to accurately predict the probability of long-term treatment success in the broader population of overweight children and adolescents and to understand more about treatment responders.

Figure 5 demonstrates results from behavioral counseling studies in adolescents^{96, 112, 113, 115, 116} with two good-quality studies particularly relevant to primary care.^{113, 116}

Figure

Figure 5. Effects of behavioral weight loss treatment on BMI for adolescents using CDC Growth Charts: United States. Body mass index-for-age percentiles: Girls, 2 to 20 years.

One short-term, primary care conducted trial used a computer-based approach to generate tailored plans for counseling of obese (above the adult BMI cutoff of 30) adolescents (aged 12 to 16) by trained and experienced pediatricians, supplemented with multiple follow-up telephone counseling calls from a qualified counselor.¹¹³ Significant but small benefits were seen in BMI measures at seven months, primarily from stabilizing BMI (eliminating BMI increases) in those receiving the intensive intervention. While the magnitude of these benefits would be understated by this design, which compared two active treatments, changes were modest (Figure 5).

Similarly, a short-term trial that would be feasible for primary care involved an Internet- and e-mail-based family intervention targeting 57 overweight (mean BMI 36.37 kg/m²) non-Hispanic black females aged 11 to 15 years with at least one obese biological parent. ¹¹⁶ Compared to a diet and physical activity education intervention, the comprehensive behavioral intervention resulted in a statistically significant difference in weight and BMI change from baseline between the two groups at six months, due largely to prevention of weight or BMI gain in the experimental group.

Although both trials showed small but statistically significant benefits in BMI measures at 6–12 months, it is not clear that these BMI changes would have clinical benefits or be sustained.

Pharmacotherapy

One randomized placebo-controlled trial of sibutramine within a comprehensive behavioral treatment program in adolescents showed superior weight change outcomes after six months (4.6 kg greater weight loss, 95% CI 2.0–7.4 kg) in an intent-to-treat analysis⁹⁴ (Figure 5). With continued use, weight loss at six months was maintained through 12 months. The rate of adverse effects and discontinuation, however, was fairly high (12% discontinued and 28% reduced the medication). It is not clear that the additional short-term weight change provided a net benefit, since changes in serum lipids, serum insulin, serum glucose, and HOMA (homeostatic model of insulin sensitivity) did not differ between the groups. Among all trial completers (63%–76% of all participants) significant improvements from baseline were seen at 12 months in HDL cholesterol, serum insulin, and HOMA. Blood pressure was not improved, and in some cases, increased blood pressure was a reason for discontinuation. We found no evidence for the use of metformin for weight loss/disease prevention in normoglycemic obese adolescents with weight outcomes after more than three months, nor did we find acceptable evidence on alternative or complementary therapies.

Surgery

No acceptable-quality evidence evaluated the effectiveness of surgical approaches to overweight in adolescents. There are no controlled treatment outcome data on bariatric surgery approaches in adolescents. Stringent NIH guidelines for surgery in the morbidly obese adolescent¹²⁰ specify strict qualification criteria and performance of surgery only in specialized centers with comprehensive weight-management programs. For mature, morbidly obese adolescents with comorbidities who meet these criteria, the evidence in adults¹²¹ may be considered as a surrogate evidence source.

Behavioral Counseling Interventions

Few (n = 3) studies reported health outcomes as defined in our analytic framework,^{103, 112, 115} and two of these were rated at least fair quality (Table 5). In one fair-quality trial, depression scores, measured using reliable and valid instruments, showed improvement from baseline in treated adolescent girls but not controls, while reliably measured self-esteem scores improved from baseline in both groups.¹¹² In a second fair-quality study, significantly fewer children aged 8–12 who received comprehensive behavioral treatment had elevated total behavior problem scores or elevated internalizing behavior problem scores at 24 months' follow-up than at baseline.¹⁰³

Behavioral Counseling Interventions

Potential eating problems or weight management behaviors were the only harms addressed in two trials. One good-quality trial reported no adverse effects on problematic eating (using validated measures for dietary restraint, eating disinhibition, problematic weight management behaviors, weight concerns, and eating disorder psychopathology) after primary care-based comprehensive behavioral treatment in 37 of 44 adolescent trial completers.¹¹³ One fair-quality trial reported no effect on eating disorder symptoms, weight dissatisfaction, or purging/restricting behaviors in 47 8- to 12-year-olds in a family-based comprehensive behavioral treatment program, using a reliable measure (Kids' Eating Disorder Survey) that has been validated in slightly older children.^{103, 122} Differences between boys (no effect) and girls (elevated total scores) were not significant, but may be revealed in studies with larger sample sizes.

Pharmacotherapy

In the placebo-controlled phase of the sibutramine trial,⁹⁴ 44% (19/43) of patients in the active medication group reduced or discontinued the medication due to elevated blood pressure, pulse rate, or both. These were the main adverse events reported.

Surgery

We attempted to estimate the rate of harms from the uncontrolled cohort literature, but found loss to follow-up (25–60% at 4–24 months)¹²³–¹²⁵, and inadequate reporting prevented us from making reasonable estimates of rates of surgery-associated harms.