Effects of the Youth Fit 4 Life physical activity/nutrition protocol on body mass index, fitness and targeted social cognitive theory variables in 9- to 12-year-olds during after-school care

James J. Annesi, Kennesaw State University
Stephanie M. Walsh
Brittney L. Greenwood
Nicole Mareno, Kennesaw State University


Aim Childhood overweight and obesity is unacceptably high in industrialised nations. School-based interventions have largely been atheoretical and ineffective. This study aimed to test a new theory-based protocol for its effects on measures of fitness and body mass index (BMI), and its proposed psychosocial mediators, during elementary after-school (out-of-school hours) care. Methods Nine- to 12-year-old participants of YMCA-based after-school care in the southeastern Unites States were randomised into either the experimental Youth Fit 4 Life (YF4L) treatment group (n = 86) or a typical care group (n = 55) for 45 min/day. YF4L is based on social cognitive theory, emphasising mastery over physical activities and the development of self-management/self-regulatory skills to support healthy behaviours. Physiological and psychosocial variables were assessed over a 9-month elementary school year. Results Of the overall sample, 28% were overweight or obese at baseline. YF4L was associated with significantly greater improvements in BMI, and measures of self-regulation, mood, self-efficacy, cardiovascular endurance and strength over both 3 and 9 months. Changes in self-regulation, mood and self-efficacy significantly mediated the treatment type–BMI relationship over both 3 months (R 2 = 0.12, P = 0.002) and 9 months (R 2 = 0.13, P = 0.001), with change in self-regulation being a significant independent mediator. Changes in BMI and self-regulation reciprocally reinforced one another. Gender was not a significant moderator of those relationships. Conclusions The YF4L treatment mitigated rise in BMI in 9- to 12-year-old enrollees of after-school care. The treatment's basis in social cognitive theory was supported. Because of its positive effects and ability to utilise existing staff, large-scale application is warranted after sufficient replication.