Summary: Excess visceral adiposity contributes to elevated cardiometabolic risk, and waist circumference is commonly used as a surrogate measure of visceral adipose tissue. Although regular aerobic exercise is known to improve abdominal obesity, its effect on waist circumference is unclear. A systematic review and meta‐analysis was performed to determine (1) the effect of aerobic exercise on waist circumference in adults with overweight or obesity; (2) the association between any change in waist circumference and change in visceral adipose tissue and/or bodyweight with aerobic exercise interventions; and (3) if reductions in waist circumference with exercise are moderated by clinical characteristics or components of aerobic exercise prescription. Twenty‐five randomized controlled trials (1686 participants) were included. Regular aerobic exercise significantly reduced waist circumference by 3.2 cm (95% confidence interval [CI] −3.86, −2.51, p ≤ 0.001) versus control. Change in waist circumference was associated with change in visceral adipose tissue (β = 4.02; 95% CI 1.37, 6.66, p = 0.004), and vigorous intensity produced superior reduction (−4.2 cm, 95% CI −4.99, −3.42, p < 0.0001) in waist circumference compared with moderate intensity (−2.50 cm, 95% CI −3.22, −1.79, p = 0.058). These findings suggest regular aerobic exercise results in modest reductions in waist circumference and associated visceral adipose tissue and that higher intensity exercise may offer superior benefit to moderate intensity.

Aim This systematic review aimed to determine the effect of aerobic exercise interventions, including high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT), on liver fat in adults. A secondary aim was to investigate the interaction between total weekly exercise volume and exercise-related energy expenditure and change in liver fat. Methods Relevant databases were searched to December 2020 for randomised trials, comparing HIIT to control, MICT to control, or HIIT to MICT. Studies were excluded if they did not implement ≥2 weeks intervention or assess liver fat using magnetic resonance-based techniques. Weighted mean differences and 95% confidence intervals (CI) were calculated. Regression analyses were undertaken to determine the interaction between weekly exercise volume in minutes and kcal with change in liver fat %. Results The search returned 28,262 studies of which 19 were included involving 745 participants. Both HIIT and MICT elicited moderate reductions in liver fat % when compared to control (HIIT:-2.85%, 95%CI:-4.86 to -0.84, p=0.005, I²=0%, n=114, low certainty evidence; MICT:-3.14%, 95%CI:-4.45 to -1.82, p<0.001, I²=5.2%, n=533, moderate certainty evidence). There was no difference between HIIT or MICT (-0.34%, 95%CI:-2.20 to 1.52, p=0.721, I²=0%, n=177, moderate certainty evidence). Neither total exercise volume in minutes (β=0.0002, SE=0.0017, Z=0.13, p=0.89) nor exercise-related energy expenditure in kcal (β=0.0001, SE=0.0002, Z=-0.63, p=0.52) were related to changes in liver fat %. Conclusion HIIT elicits comparable improvements in liver fat to MICT despite often requiring less energy and time commitment. Further studies should be undertaken to assess the relative importance of aerobic exercise prescription variables, such as intensity, on liver fat.