medwireNews: The optimal exercise for improving insulin resistance in children and adolescents with overweight is a minimum of two to three 60-minute sessions per week of high-intensity interval training (HIIT) with or without resistance training, suggests a systematic review and extensive network meta-analysis.
The analysis included 55 studies involving a total of 3051 children and adolescents, 50.4% girls, with a mean age of 13.5 years. Most of the studies were randomized trials comparing at least one exercise intervention – aerobic or endurance, resistance or strength training, concurrent training (aerobic and resistance training), or HIIT – for at least 4 weeks with no treatment, usual care or education, and included both boys and girls.
The participants had overweight or obesity, which was mostly defined based on age- and sex-specific BMI cut-off points.
The results, published in JAMA Pediatrics, showed that physical exercise was associated with a significant mean reduction in fasting insulin of 4.38 µU/mL compared with the control intervention. There was also a significant mean reduction in homeostatic model assessment for insulin resistance (HOMA-IR) of 0.87, increasing to a 1.36 reduction among participants who had levels of 3.16 or greater at baseline.
There was no significant association between physical exercise and fasting glucose, 2-hour oral glucose tolerance or glycated haemoglobin levels.
Antonio García-Hermoso (Universidad Pública de Navarra, Pamplona, Spain) and colleagues highlight that the association between exercise and fasting insulin and HOMA-IR was “nonlinear” and to achieve the “clinically meaningful” reduction in fasting insulin required a minimum of about 900 metabolic equivalent of task minutes (MET-min) per week of physical exercise, with a levelling off seen at around 1500 MET-min per week.
For HOMA-IR, the minimum level of exercise needed was 1200 MET-min per week, but in this case, higher levels of exercise were associated with continued improvements, particularly among children with starting levels of 3.16 or above.
The researchers note that 900 to 1200 MET-min/week is “equivalent to two to three 60-minute sessions of moderate to vigorous activity per week.”
Improvements in fasting insulin levels were seen across all types of exercise, with significant mean reductions compared with the control intervention of 1.42 µU/mL with aerobic training, 2.70 µU/mL with concurrent training and 4.98 µU/mL with HIIT/resistance training.
This was similar for HOMA-IR levels, with mean reductions of 0.70 with aerobic training, 0.87 with HIIT, 1.03 with concurrent training and 1.20 with HIIT/resistance training. And for fasting glucose levels, with significant mean reductions of 1.43 mg/dL for aerobic training, 2.81 mg/dL for concurrent training and 5.01 mg/dL for HIIT/resistance training.
Ranking these exercise interventions by type, García-Hermoso et al found that HIIT/resistance training ranked the highest for fasting insulin levels, HOMO-IR, and fasting glucose levels, with a surface under cumulative ranking of 94.7%, 95.1% and 93.9%, respectively. Concurrent training ranked second.
“Performing HIIT, with or without resistance training, induces metabolic stress on the muscles, leading to increased glucose uptake”, consequently improving insulin resistance, the researchers explain. They add that concurrent training “is more efficient for increasing lean body mass and adiponectin concentration compared with aerobic training alone.”
The investigators note that, on average, the certainty of evidence that their findings are based on “varied from low to moderate.”
They therefore conclude: “It will be crucial to further investigate and establish minimum physical activity recommendations that effectively address insulin resistance, prevent metabolic syndrome, and reduce type 2 diabetes risk in this specific population.”
By Lucy Piper
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