Across 41 studies (n = 1,517; 24 meta-analyzed) of supervised exercise without diet or drug co-interventions in fatty liver disease, resistance training produced the largest drop in liver fat (SMD -0.77, 95% CI -1.14 to -0.39), followed by moderate-intensity aerobic exercise (SMD -0.50, CI -0.95 to -0.04). High-intensity interval training showed no clear effect. Liver enzymes moved inconsistently, aerobic work improved transaminases and triglycerides, resistance training improved fasting glucose and HDL, and BMI, body fat and HbA1c barely changed. Certainty of evidence was low to very low.
The most useful finding is the dissociation: liver fat fell without meaningful weight or adiposity change. That fits mechanistic work suggesting muscle contraction improves hepatic fat handling and insulin sensitivity independent of the scale, which should reassure people who exercise faithfully and see no weight loss. Resistance training edging out aerobic work is notable, since guidelines have historically leaned on cardio, and lifting is often more feasible for people with joint pain or low fitness. The HIIT null result deserves caution; small, heterogeneous trials may simply be underpowered. The limits are serious: low-to-very-low certainty, mixed randomized and nonrandomized designs, short durations, and liver fat as a surrogate rather than outcomes like cirrhosis, cardiovascular events or mortality. Editorially, this is confirmatory rather than paradigm-shifting. It supports prescribing either resistance or moderate aerobic exercise for MASLD now, while the authors rightly say exact dose and modality recommendations await better trials.