The standout finding of this study was that, despite similar reductions in body weight and fat mass in COMBO and ADF, reductions in liver fat were greater in COMBO, suggesting that just losing weight isn’t the only important factor for reducing liver fat. To maximize these reductions, it may be pivotal to combine a hypocaloric diet with exercise.

That said, this finding (i.e., a greater reduction in liver fat in COMBO compared to ADF) was technically nonsignificant, so further trials utilizing a similar design are needed. In the meantime, other research can shed light on the question of whether exercise reduces liver fat independent of changes in body weight. If this is indeed the case, it’s possible that exercise truly had an additive effect in the summarized study.

Fortunately, this subject is quite well studied. Multiple trials have reported that exercise significantly decreases liver fat independent of weight loss.^[2]^[3]^[4] According to a 2018 meta-analysis, in the absence of significant weight loss, exercise interventions reduce liver fat by 2.16%, on average, in people with NAFLD.^[5] However, the addition of significant weight loss still produced larger reductions in liver fat.

The evidence is pretty clear that exercise can reduce liver fat independent of weight loss, but how much exercise is needed? The summarized study utilized a relatively demanding moderate-intensity aerobic exercise protocol (300 minutes per week), which may be an unsustainable approach for many people. This may have been why, although there were no dropouts in COMBO, 25% of the participants assigned to EX dropped out.

After 3 months, the summarized study found a nearly 5.5% reduction in liver fat in the COMBO group, which is on par with reductions yielded by other lifestyle intervention with considerably less exercise volume. In an observational study that instructed participants (including 50 with NAFLD) to reduce their energy intake and perform aerobic exercise that only moderately increased heart rate for at least 180 minutes per week, participants reduced liver fat by 4.6% over 9 months.^[6] Similarly, a randomized controlled trial in participants with NAFLD reported that two to three sessions of supervised nordic walking per week (performed at 60–75% of VO₂max for 30–60 minutes) combined with a dietary intervention reduced liver fat by 7.6%.^[7] Finally, evidence from a couple of meta-analyses indicate that exercise interventions (without dietary interventions in most studies) involving roughly three sessions of 30–60 minutes of aerobic exercise per week for 12 weeks significantly reduced liver fat.^[5]^[8] One of these meta-analyses reported an average reduction in liver fat of 3.3%.^[5]

In sum, less demanding exercise interventions than used in the summarized study seem to be able to promote similar reductions in liver fat. At the moment, there doesn’t appear to be a clear relationship between reductions in liver fat and the weekly frequency and volume of exercise in people with NAFLD.^[9]

Exercise type may also play a role. The present study used prolonged moderate-intensity aerobic exercise, which may not suit many people’s preferences.

A 2017 meta-analysis reported that aerobic and resistance exercise interventions produce similar reductions in liver fat in people with NAFLD, even though energy expenditure tended to be lower in resistance exercise interventions.^[8]

Additionally, the following results have been reported in trials that performed head-to-head comparisons between different exercise interventions in participants with NAFLD:

4 weeks of either moderate-intensity aerobic exercise (55% of VO₂max) or high-intensity interval aerobic exercise (repeated cycles of 4 minutes at 80% of VO₂max followed by 3 minutes at 50% of VO₂max), which were matched for energy expenditure (about 400 kcal per session), produced similar reductions in liver fat.^[10]
6 months of either moderate-intensity aerobic exercise (45%–55% of maximum predicted heart rate for 150 minutes per week) or vigorous aerobic exercise (65%–80% of maximum predicted heart rate for 150 minutes per week) produced similar reductions in liver fat.^[11]
4 months of either aerobic exercise (60%–65% of heart rate reserve for 180 minutes per week) or resistance exercise (three full-body sessions per week consisting of 9 exercises performed for 3 sets of 10 repetitions using 70%–80% of 1-repetition maximum) produced similar reductions in liver fat.^[12]
3 months of either aerobic exercise (60%–75% of VO₂max for 180 minutes per week) or resistance exercise (three full-body sessions per week consisting of 10 exercises performed for 2 sets of 8–12 repetitions to fatigue each) produced similar reductions in liver fat.^[13]

Although head-to-head comparisons are sparse, the available evidence indicates that different types of exercise have similar effects on reducing liver fat. Further research is needed to clarify the most effective form of exercise for reducing liver fat, as well as the ideal amount of exercise. Moreover, it remains unclear whether combining aerobic and resistance exercise is superior to either mode of exercise alone for reducing liver fat.^[9]

However, as it stands, the available evidence indicates that various types of exercise interventions can be used to reduce liver fat. Thus, the general recommendation to accumulate at least 150 minutes of moderate-intensity or 75 minutes of high-intensity exercise per week is a suitable target for most people.^[9] Following this recommendation, the mode, frequency, and duration of exercise should be customized to the individual’s preferences and goals to maximize adherence.

Alternate-day fasting and exercise for reducing liver fat Original paper