Background: Physical activity (PA) reduces visceral adipose tissue (VAT) in adults; however, the dose to reduce VAT in youth is unclear. Objective: To examine whether high intensity PA preferentially reduces waist circumference (WC) and VAT compared to lower intensity PA. Design: Randomized controlled trial. Participants: Youth were 13-18yrs, overweight, with one additional risk factor for type 2 diabetes (T2DM).
Intervention: 6-months, exercising 3 times/week at a high intensity (70-85% of Heart Rate Reserve HRR), or low intensity (40-55% HRR). Primary outcome: VAT (cm2) measured by MRI at L4-L5, and WC at the height of the iliac crest (cm). Results: 94 Youth were randomized to either high intensity (n=30); low intensity (n=32) or control (n=32). Changes in WC and VAT were not significant across groups. A trend towards a reduction in VAT in the training groups, compared to controls was demonstrated in sub-analysis (-14.3 ± 9.6 % vs. +0.01 ± 0.4 %, p= 0.059). Peak fitness increased significantly in both the high and low intensity arms (1.3 ± 0.6 and 1.4 ± 0.6 ml/kg/min, p < 0.05). Conclusions: Training at 55-65% HRR improves fitness by ~10%, and ~2 days/week elicits modest non-significant reductions in VAT in overweight youth.