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Educating the Student Body
found no effect (Dobbins et al., 2009). And in a meta-analysis pertaining to 
prospective, randomized, and nonrandomized clinical trials of school-based 
physical activity interventions that lasted at least 6 months, no effects on 
BMI were found (Harris et al., 2009).
Taken together, the evidence concerning the effects of school-based 
physical activity interventions and their observational associations with 
BMI, overweight, and obesity is inconsistent. While some studies docu-
ment no effects on body weight, others report significant associations with 
measures of skinfolds and percent body fat, and some document significant 
relationships with BMI. There are several possible explanations for these 
inconsistent findings. First, body weight can increase among participants 
in physical activity interventions, as observed in a 4-year physical educa-
tion intervention among students in elementary schools. In that study, stu-
dents in the intervention experienced greater annual increases in fat mass 
compared with the controls (Lofgren et al., 2012). Additionally, physical 
activity/physical education interventions may not increase the frequency 
and intensity of physical activity sufficiently to have the desired impacts on 
children’s body weight (Dobbins et al., 2009). Moreover, interventions may 
not last long enough to have a measurable impact on children’s BMI, over-
weight, or obesity. The inconsistency in the evidence concerning the effects 
of physical education and physical activity on body weight among children 
and adolescents merits additional investigation. Future studies should be 
of longer duration and include programs that entail higher frequency and 
greater intensity of physical activity.