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Paed Obesity – Improved cardiovascular health

Evidence Summary
A meta-analysis from pooled results of randomised trials on exercise intervention alone with blood lipid measurements as an outcome in overweight and obese adolescents, demonstrated no conclusive difference in total cholesterol, triglycerides, HDL (high density lipoprotein) and LDL (low density lipoprotein)[1]. Almost all of the studies that used exercise only interventions were of poor quality in this meta-analysis.

In contrast, a systematic review of obese children <14 years old that had aerobic exercise alone (127 subjects) as an intervention had a decrease of LDL-cholesterol of -0.49 with a 95% confidence interval (CI) of -0.76 to -0.21[2]. The systematic review found that combined exercises (aerobic, strength and flexibility) had a moderate effect to improve HDL-cholesterol of 0.50 (95% CI 0.11 to 0.88), and two studies showed at least 60 minutes duration of combined exercises led to greater improvements in HDL-cholesterol of 0.53 (95% CI 0.09 to 0.97). Subgroup analysis identified an improvement of HDL-cholesterol of 0.74 (95% CI 0.23 to 1.26) when aerobic exercise program was at an intensity of <75% of maximum heart rate – so obese children may require lower intensities to generate such improvements. Furthermore, exercise programs of more than 3000 minute total duration of volume of exercise were only effective for lowering triglycerides by -0.61 (95% CI -0.92 to -0.30) possibly because a greater volume of physical activity does not directly influence the metabolism of lipoproteins.

A meta-analysis in 2015 of 6 vascular function studies with 219 overweight or obese children that were given at least 6 weeks of aerobic exercises with or without resistance exercises, found a mean difference in flow mediated dilatation of 1.54% (95% CI 0.24 to 2.84), which favours exercise over controls[3]. Moreover, the mean difference in cardiorespiratory fitness was 3.64 mL/kg/min (95% CI 1.57 to 5.7) significantly favouring exercise. Exercise training instigated an improvement in endothelial function, but the results needed to be interpreted with caution as the studies were heterogeneous with small sample sizes, and one study included a diet education programme. A more recent (2017) meta-analysis of randomised controlled trials of carotid arterial wall thickness in the obese paediatric population discovered a significant reduction in carotid intima-media thickness (IMT) of -0.306 (95% CI -0.540 to -0.072) in the physical activity groups[4]. Exercise programs with longer duration per week showed a greater decrease in carotid IMT of -0.060 (95% CI -0.136 to -0.015).

Aerobic fitness in obese children has been evaluated by a meta-analysis in 2011 which found an increase in peak VO¬2 of 0.46 (95% CI 0.18 to 0.74) in aerobic exercise groups compared to control groups[5]. Programs of more than 12 weeks > 3 times per week and >3000 minutes of total exercise time showed better post-treatment improvements. However, there were no differences in peak VO2 between combined exercise (aerobic and resistance) groups and controls 0.15 (95% CI -0.17 to 0.48), possibly because combined exercise groups had an emphasis on strength gains that may not impact on peripheral oxygen extraction[5].

The beneficial effects of aerobic exercise on resting blood pressure in obese children have been evaluated by a meta-analysis published in 2013[6]. It identified decreases in systolic BP to -0.46 (95% CI -0.66 to -0.27) and diastolic BP -0.35 (95% CI -0.60 to -0.10) in the exercise intervention groups compared to controls. The greatest improvements in systolic blood pressure were those interventions with an exercise frequency of three sessions weekly lasting longer than 60 minutes.

Quality of Evidence
Grade B – Moderate – there are some limitations to the RCTs in these meta-analyses.

Strength of Recommendation
Grade 1- Strong – there is a clear positive balance of benefit of exercise for cardiovascular health in the paediatric overweight or obese population.

Conclusion
Physical activity interventions involving an aerobic component in the obese or overweight paediatric population can improve blood lipid profile, aerobic fitness, and blood pressure. There is also evidence for positive changes related to vascular function. Longer term studies and the optimal exercise program to assess the clinical relevance of these findings are required
References

  1. Efficacy of exercise intervention for weight Loss in overweight and obese Adolescents: metaanalysis and Implications
    Stoner L, Rowlands D
    Sports Med. 2016 Nov; 46(11):1737-1751.
  2. Improvement of the lipid profile with exercise in obese children: a systematic review
    Escalante Y, Saavedra JM et al
    Prev Med. 2012 May; 54(5):293-301.
  3. Exercise and vascular function in child obesity: a meta-analysis
    Dias KA, Green DJ et al
    Pediatrics. 2015 Sep; 136(3):e648-59
  4. Effects of exercise on carotid arterial wall thickness in obese pediatric populations: a meta-analysis of randomized controlled trials
    Garcia-Hermoso A, Gonzalez-Ruiz K et al
    Child obes. 2017 April; 13(2):138-145
  5. Improvement of aerobic fitness in obese children: a meta-analysis
    Saavedra JM, Escalante Y et al
    Int J Pediatr Obes. 2011 Aug; 6(3-4):169-77
  6. Effects of exercise on resting blood pressure in obese children: a meta-analysis of randomized controlled trials
    Garcia-Hermoso A, Saavedra JM et al
    Obes Rev. 2013 Nov; 14(11):919-28

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