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School-based childhood obesity interventions

This is an excerpt from Science of Long-Term Weight Loss, The by Timothy Lohman & Laurie A. Milliken.

School-Based Obesity Interventions
There have been many school-based approaches to treating childhood obesity, since children spend their days in school and consume one or more meals there. One of the most ambitious studies in childhood obesity was the Pathways study. This was a large multicenter trial involving over 1,500 Native American children, where a large group of investigators developed a 3-year intervention beginning with the third grade and ending in the fifth grade. Many of these children were already at risk for obesity or were obese. The average percent fat of these third graders was 32%, and 28.9% of these children were above the 95th percentile compared with a national sample where only 11% of children were above the 95th percentile (Caballero et al. 2003).

The obesity intervention approach of Pathways included four components: school curriculum, food services, physical activity, and family. All four components took place on school grounds. Children from seven Native American communities in the United States participated in this study (Caballero et al. 2003). During the 3-year intervention, the heights and weights of all children were evaluated each year, with 21 schools participating in the intervention and 20 schools participating as controls. Body fat was measured initially at the beginning of third grade and at the end of fifth grade. Unfortunately, children in both the intervention and the control schools averaged an increase of 7% fat from 32% to 39% over the 3 years, with no significant effect of the intervention. Significant changes in psychosocial factors, in food service practices, and in physical activity occurred over the 3-year intervention period in favor of the intervention schools. Also, the fat content of the diet (measured using diet recalls) for school lunches was lower for children in the intervention schools. The family component involved regularly scheduled demonstration events at the school throughout the 3-year intervention.

Joel Gittelsohn, from the Center for Human Nutrition at Johns Hopkins University in Baltimore, Maryland, and a coinvestigator of the Pathways study, coordinated the formative research across four field centers and managed the work in two Apache tribes. When asked to reflect on this study, he stated that they did a good job while students were in school for both healthy eating and physical activity; however, the family component should have been expanded to work more closely with individual families, and with a low rate of participation, many families were not reached (Gittelsohn et al. 2003). The Pathways intervention did not extend beyond the school grounds, and positive changes within schools were likely offset by features of the community food and physical activity environment. Thus the Pathways intervention apparently did not have sufficient overall impact on the food intake and physical activity levels of the children to produce an effect on obesity.

Gittelsohn and his colleague, Mohan Kumar (2007), reviewed many studies focusing on the school environment, pointing out the limitations of study results in preventing childhood obesity. They noted that the food environment of the child includes family meals, supermarkets and small convenience stores, and fast-food restaurants along with the school cafeteria. They developed the concept of healthy eating zones around schools as an important potential intervention component often not included in school interventions. Formative research is also a key strategy for developing a culturally appropriate and effective intervention, yet it was not described in many studies. They argued that parental and community interventions will be necessary in future obesity prevention studies.

Several years later, Mary Story (previously one of four investigators on the Pathways study) and colleagues carried out a 2-year intervention (Project Bright Star) in kindergarteners and first graders in 14 Native American schools (Story et al. 2012). At baseline, the children averaged 19.5% fat, with a BMI of 16.7 kg/m2. After the 2-year intervention, both groups increased in body fat by about 4%. The main difference between the intervention and control groups was in the prevalence of overweight but not the obese categories (based on BMI), with the intervention having a significantly smaller incidence of overweight. No follow-up was carried out, so it is not known whether the observed changes were sustained.

Another large school-based intervention of 3 years in 42 schools (21 intervention schools) with 54% Hispanic and 18% non-Hispanic Black children was carried out at seven field sites around the country (Group et al. 2010). The BMI z-score decreased more in the intervention schools than in the control schools along with the percentage of students with waist circumference greater than the 90th percentile. BMI percentiles greater than the 85th percentile showed a similar decrease of 4% in both the intervention and control schools (primary study outcome). In the control schools, the BMI percentile decreased, which was unexpected. Fasting insulin in the control group increased by about 4%, which was significantly greater than in the intervention group. All three of the interventions were insufficient for producing body composition changes in young children.

Three other school-based programs (SPARK, TAAG, CATCH) were aimed primarily at physical activity, with changes in body weight or percent fat as a secondary outcome. In each case, body fat or BMI did not decrease in children of elementary or middle school age in response to the intervention (Nader et al. 1999). In Sports, Play and Active Recreation for Kids (SPARK), a 2-year physical activity intervention for fifth and sixth graders (Sallis et al. 1997), there were no effects on skinfolds or after-school physical activity, but the study showed significant increases in physical activity performed during physical education classes.

In a 2-year physical activity intervention (Trial of Activity for Adolescent Girls, TAAG, funded by the National Institutes of Health) in 36 schools in six regions of the United States, a small increase was measured in physical activity (assessed by accelerometry) in middle school girls, but there was no effect on physical fitness or obesity. This multicenter randomized study illustrated the difficulties of changing physical activity in a population where activity levels usually decline. If physical activity cannot be easily increased with an extensive school-based intervention including many resources over a 2-year period, a more general public health approach may not be effective (Webber et al. 2008).

One of the longest follow-ups to a school-based intervention, the Child and Adolescent Trial for Cardiovascular Health (CATCH), was carried out by Nader and colleagues (1999). This study is an exception to the general lack of follow-up in school-based interventions. A 3-year follow-up of the CATCH 3-year intervention was carried out. The CATCH intervention was designed to modify school lunches and increase physical activity to improve cardiovascular health in 56 intervention and 40 control schools during grades three through five. The longitudinal follow-up measured eating and activity attitudes and behaviors and cardiovascular disease risk factors (Nader et al. 1999). Nader indicated that the behavioral changes found at the end of fifth grade persisted through to the eighth grade, including a decrease in energy intake and an increase in level of physical activity in the intervention schools.

A comprehensive review of the health benefits of physical activity and fitness in school-aged children and youth (Janssen and Leblanc 2010) led to three recommendations: (1) achieving 60 minutes per day of moderate-intensity physical activity, (2) adding vigorous-intensity activities when possible for muscle and bone benefits, and (3) making sure that aerobic activities make up the majority of physical activity (Janssen and Leblanc 2010). Also, the review of school-based physical activity programs by Dobbins and colleagues (2013) found small effects on behavior and physical activity levels and the need to design longer-term studies.

Tamara Brown reviewed 59 school-based interventions and found that 21 studies (31%) significantly improved BMI scores as compared with control schools. Interventions that combined diet and physical activity had the greatest BMI effect (11 of the 28 studies were significant for BMI). In her recommendations for future studies, Brown states the following:
Many new policy interventions are community-based and multilevel; multicomponent interventions are required that involve the school, family and wider community. It would be interesting to evaluate how school-based elements of such intervention “fit” and interact within the wider community and family. (Brown 2011, 677)

Doak and colleagues (2006) carried out a comprehensive review of 25 school-based interventions and rated 17 as effective based on either height and weight or skinfold statistical comparisons (Doak et al. 2006). The authors concluded their review with nine recommendations to improve future intervention research studies. Two critical recommendations, rarely carried out in research studies, are to emphasize long-term sustainability and to report the frequency distribution for BMI and adiposity measures in response to the intervention for the whole target population.

The addition of these recommendations would provide an understanding of long-term success, which is the overall goal of a weight loss plan. Providing the frequency distribution for BMI and fatness gives information about to whom the results can be applied as well as showing the variability of the BMI or fatness changes, since there can be considerable variability in the response to the intervention.

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