No other behaviors were targeted in the study in order to “isolate” the specific effects of reduced television viewing on changes in BMI. In addition to the classroom curriculum, parents also received newsletters and a television time-management monitor that allowed them to set time limits on the home television; 42 percent of parents reported that they actually installed the device. Results revealed significant reductions in BMI, triceps skinfold thickness, waist circumference, and waist-to-hip ratios among children in the intervention school compared with children in the control school, over a single school year.
The Planet Health intervention—a curriculum-based intervention for sixth- and seventh-grade students using behavioral choice and social cognitive approaches (discussed earlier)—also focused on reducing television viewing (Gortmaker et al., 1999). Other lessons included an emphasis on dietary and physical activity change. Teacher training sessions were held prior to implementation. Obesity prevalence decreased in girls in the inter-vention schools (from 23.6 percent to 20.3 percent) and increased in girls in the control schools (from 21.5 percent to 23.7 percent). For boys, obesity prevalence decreased in both groups, with no significant differences between groups. Number of television hours declined for both genders in the intervention schools as compared with controls and for girls in the intervention schools there was an increase in fruit and vegetable consumption.
The positive results of Stanford SMART and Planet Health suggest that obesity prevention efforts should involve reductions in sedentary television viewing time (see Chapter 8) and that school curricula should include television viewing reduction components.
Evidence from school intervention studies demonstrates some effectiveness of behavior-based nutrition and physical activity curricula. Evidence is most compelling from curricula for reducing television viewing, from vigorous PE interventions, and from large-scale, multicomponent intervention studies.
The extent to which schools are currently implementing such curricula, however, is unclear. Constraints include the limited availability of health educators who are trained in behavior-change methods, and the lack of sufficient time in the school day for specifically focusing on eating and physical activity behaviors. More staff training and the allocation of more time are two priorities. The impact of health education material can also be expanded by incorporating nutrition and physical activity information into science, math, history, social studies, and other courses.
Schools should ensure that nutrition, physical activity, and wellness concepts are taught throughout the curriculum from kindergarten through