Sports Med 2019 Jan;49(1):83-94
Department of Exercise Science, University of South Carolina, Columbia, SC, 29208, USA.
Background: A recent meta-analysis reported that exercise interventions are effective for promoting weight loss in adolescents with overweight-obesity. However, the meta-analysis did not investigate whether there is an optimal exercise dose for promoting weight loss in overweight and obese adolescents. A common method of expressing exercise dose is the calculation of metabolic equivalents (METs), expressed as MET-h/week.
Objectives: The objective of this study was to determine the association between exercise dose (MET-h/week) and weight loss [body weight, body mass index (BMI)] in adolescents with overweight-obesity.
Data Sources: Trials included in the original meta-analysis were extracted, and a subsequent search to identify studies published between May 2015 and May 2018 was conducted. The search included electronic databases (PubMed, Web of Science SPORTDiscus, Google Scholar) and the reference lists of eligible articles and relevant reviews.
Study Selection: The inclusion criteria were as follows: (i) randomized controlled trial; (ii) structured exercise intervention, alone or combined with other intervention components; (iii) control group received no structured exercise or behavioral modification designed to increase physical activity; (iv) participants overweight or obese (BMI ≥ 85th percentile); and (v) participants aged between 10 and 19 years.
Appraisal And Synthesis Methods: Fifteen trials were extracted from the original meta-analysis. The current search identified an additional five trials (three articles). Data from 20 trials (16 articles) involving 1091 participants (54% female, 17% not reported) were included in the analysis. Effect sizes were reported as mean difference, and random effects meta-regression quantified the association between exercise dose and weight loss. Study quality was assessed using a modified Jadad's scale.
Results: Total body weight change (decrease) ranged from - 2.7 to 19.3 (median 2.5) kg, and BMI change (decrease) ranged from - 1.6 to 6.3 (median 0.9) kg/m. MET-h/week ranged from 5.4 to 36.0 (median 6.0). Each MET-h/week was associated with a 0.13 kg/m (95% confidence interval [CI] 0.08-0.19) and 0.33 kg (95% CI 0.08-0.59) decrease in BMI and body weight, respectively.
Limitations: The prescribed exercise dose for the majority of trials was low. As such, we were unable to discern whether there was an optimal exercise dose for weight loss (i.e., if the association between dose and weight loss was non-linear). Additionally, most trials had small sample sizes (median n = 34) and 17 trials had methodological limitations.
Conclusions: Each MET-h/week was associated with a 0.13 kg/m and 0.33 kg decrease in BMI and body weight, respectively. While this relationship appears to be linear, i.e., no optimal exercise dose, it should be emphasized that the exercise prescription dose for the majority of trials was low. Subsequent trials, with greater exercise dosage, are required to determine whether there is an 'optimal' dose for promoting weight loss in adolescents with overweight-obesity. However, the current findings lend support to the use of exercise prescription for promoting weight loss and improving health outcomes in this population.