The impact of a 3-year after-school obesity prevention program in elementary school children.
BACKGROUND
Children tend to be sedentary during the after-school hours, and this has deleterious effects on their health. The objective of the present study was to determine the effects of a 3-year after-school physical activity (PA) program, without restriction of dietary energy intake, on percent body fat (%BF), cardiorespiratory fitness (CRF), and cardiometabolic markers in children.


METHODS
A cluster randomization design was employed. A total of 574 3rd grade children from 18 elementary schools in the southeastern United States participated. The intervention consisted of 80 minutes of age-appropriate moderate-to-vigorous PA each school day. The main outcomes of interest were %BF measured by dual-energy X-ray absorptiometry; CRF measured by heart rate in response to a submaximal step test; nonfasting total and high-density lipoprotein cholesterol (HDL-C); and resting blood pressure (BP).


RESULTS
Intent-to-treat analyses showed significant treatment by time interactions for %BF (p = 0.009) and CRF (p = 0.0003). The change pattern of the means suggested that %BF and CRF in intervention children improved relative to control children during the school months, rebounding to the levels of control children over the summers following years 1 and 2. Year-by-year analyses of what occurred during the months when the program was offered revealed dose–response relations for %BF and CRF, such that the clearest beneficial effects were seen for those youth who attended at least 60% of the after-school sessions. No significant intervention effects were seen for cholesterol or BP.


CONCLUSIONS
An after-school PA program was effective in reducing adiposity and improving CRF, especially in the children who attended the sessions at least 3 days/week. However, the favorable effects on %BF and CRF were lost over the summer. Thus, it is critical to incorporate strategies that attract and retain the children to receive an adequate dose of PA year-round.
Department of Health and Kinesiology, University of Texas at San Antonio, 6900 North Loop 1604 West, San Antonio, TX 78249, USA. zenong.yin@utsa.edu
Zenong
Z
Yin
Justin B
JB
Moore
Maribeth H
MH
Johnson
Marlo M
MM
Vernon
Bernard
B
Gutin
D015502:Absorptiometry, Photon / Q000379:methods; D050154:Adiposity; D000293:Adolescent; D001794:Blood Pressure; D002648:Child; D002652:Child Behavior / Q000502:physiology; D008076:Cholesterol, HDL / Q000097:blood; D005080:Exercise Test / Q000379:methods; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009765:Obesity / Q000097:blood / Q000175:diagnosis / Q000503:physiopathology / Q000517:prevention & control / Q000523:psychology; D010806:Physical Education and Training / Q000379:methods* / Q000458:organization & administration; D010809:Physical Fitness / Q000502:physiology*; D015397:Program Evaluation; D012572:School Health Services / Q000458:organization & administration*; D012574:Schools; D057185:Sedentary Behavior; D015144:Southeastern United States
D008076:Cholesterol, HDL