Effects of sprint interval training on ectopic lipids and tissue-specific insulin sensitivity in men with non-alcoholic fatty liver disease

Purpose This study examined the feasibility of sprint interval exercise training (SIT) for men with non-alcoholic fatty liver disease (NAFLD) and its effects on intrahepatic triglyceride (IHTG), insulin sensitivity (hepatic and peripheral), visceral (VAT) and subcutaneous adipose tissue (ScAT). Methods Nine men with NAFLD (age 41 ± 8 years; BMI 31.7 ± 3.1 kg m −2 ; IHTG 15.6 ± 8.3%) were assessed at: (1) baseline (2) after a control phase of no intervention (pre-training) and (3) after 6 weeks of SIT (4–6 maximal 30 s cycling intervals, three times per week). IHTG, VAT and ScAT were measured using magnetic resonance spectroscopy or imaging and insulin sensitivity was assessed via dual-step hyperinsulinaemic-euglycaemic clamp with [6,6-D2] glucose tracer. Results Participants adhered to SIT, completing ≥ 96.7% of prescribed intervals. SIT increased peak oxygen uptake [ V ˙ O 2 peak: + 13.6% (95% CI 8.8–18.2%)] and elicited a relative reduction in IHTG [− 12.4% (− 31.6 to 6.7%)] and VAT [− 16.9% (− 24.4 to − 9.4%); n = 8], with no change in body weight or ScAT. Peripheral insulin sensitivity increased throughout the study ( n = 8; significant main effect of phase) but changes from pre- to post-training were highly variable (range − 18.5 to + 58.7%) and not significant ( P = 0.09), despite a moderate effect size ( g * = 0.63). Hepatic insulin sensitivity was not influenced by SIT. Conclusions SIT is feasible for men with NAFLD in a controlled laboratory setting and is able to reduce IHTG and VAT in the absence of weight loss.