High-intensity interval on par with moderate-intensity continuous training for liver fat reduction

A high-intensity interval training (HIIT) leads to improvements in liver fat similar to those with moderate-intensity continuous training (MICT) despite often requiring less energy and time commitment, reports a recent study.

In this systematic review and meta-analysis, the investigators determined the effect of HIIT vis-à-vis MICT on liver fat in adults and examined the interaction between total weekly exercise volume and exercise-related energy expenditure and change in liver fat.

The team searched relevant databases up to December 2020 for randomized trials that compared HIIT to control, MICT to control, or HIIT to MICT. Studies that did not implement ≥2 weeks’ intervention or assess liver fat using magnetic resonance-based techniques were not included in the analysis.

The investigators calculated the weighted mean differences and 95 percent confidence intervals (CIs). They also performed regression analyses to determine the interaction between weekly exercise volume in minutes and kilocalories (kcal) with change in liver fat content.

A total of 28,268 studies were screened, of which 19 (n=745 participants) met the eligibility criteria.

Both HIIT and MICT resulted in moderate reductions in liver fat content when compared to control (HIIT: ‒2.85 percent, 95 percent CI, ‒4.86 to ‒0.84; p=0.005; I², 0 percent; n=114; low-certainty evidence; MICT: ‒3.14 percent, 95 percent CI, ‒4.45 to ‒1.82; p<0.001; I², 5.2 percent; n=533; moderate-certainty evidence).

No difference was observed between HIIT and MICT (‒0.34 percent, 95 percent CI, ‒2.20 to 1.52; p=0.721; I², 0 percent; n=177; moderate-certainty evidence).

Both total exercise volume in minutes (β, 0.0002; SE, 0.0017; z, 0.13; p=0.89) and exercise-related energy expenditure in kcal (β, 0.0003; SE, 0.0002, z, 1.21; p=0.23) were not associated with changes in liver fat content.

“Further studies should be undertaken to assess the relative importance of aerobic exercise prescription variables, such as intensity, on liver fat,” the investigators said.