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PLoS One. 2014 Dec 5;9(12):e114732. doi: 10.1371/journal.pone.0114732. eCollection 2014.

The outcomes of a 12-week Internet intervention aimed at improving fitness and health-related quality of life in overweight adolescents: the Young & Active controlled trial.

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Norwegian School of Sport Sciences, Oslo, Norway; Oslo and Akershus University College of Applied Sciences, Oslo, Norway.
Oslo and Akershus University College of Applied Sciences, Oslo, Norway.
Norwegian School of Sport Sciences, Oslo, Norway.



Overweight and obesity among adolescents may have consequences, with potentially lasting effects on health and health-related quality of life (HRQoL). Excess weight is also associated with decreases in physical activity and cardiorespiratory fitness. The aim of the current study was to investigate the short-term effects of a 12-week Internet intervention in a primary care setting intended to increase cardiorespiratory fitness and HRQoL among overweight and obese adolescents.


In this controlled trial, participants (13-15 years) were non-randomly allocated to an intervention- or a control group. The intervention group received 12-weeks access to an online program providing tailored physical activity counseling based on principles from Self-determination Theory and Motivational Interviewing. The control group received standard follow-up by the school nurses. The primary outcome measure of cardiorespiratory fitness was determined using a shuttle run test. The secondary outcomes: HRQoL, leisure time exercise, body image and self-determined motivation for physical activity and exercise, were assessed by self-report measures. Age- and gender-adjusted body mass index (BMI) was calculated based on measurements of height and weight. To compare pre-to post intervention differences within groups, a paired samples t-test was used while crude differences between groups were analyzed with an independent samples t-test.


Of the 120 participants, 108 completed the study, 75 in the intervention group and 33 in the control group. Exposure to the intervention had a small effect on cardiorespiratory fitness (0.14; 95% CI [0.01;0.28]; P = 0.04), and a moderate effect on HRQoL (5.22; 95% CI [0.90; 9.53]; P = 0.02). Moreover, the control group increased significantly in BMI, yielding a moderate preventive effect on BMI (-0.39; 95% CI [-0.74;-0.03]; P = 0.03) for the intervention group.


The results suggest that the Internet intervention with tailored physical activity counseling can have beneficial short-term effect on cardiorespiratory fitness, HRQoL and BMI among adolescents with overweight and obesity.


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