Aerobic exercise reduces liver fat and visceral adipose tissue (VAT) by a small amount even in individuals who do not experience clinically significant weight loss. There appears to be no difference between aerobic exercise dose or intensity with regard to efficacy of liver fat reduction.
Shelley E. Keating, a PhD student from the University of Sydney in Australia, and colleagues published the results of their randomized placebo-controlled study published online April 7 in the Journal of Hepatology.
The researchers tested the effects of commonly prescribed doses of aerobic exercise training over the course of 8 weeks and compared them with outcomes in the placebo group. The exercise groups consisted of low- to moderate-intensity, high-volume aerobic exercise (LO:HI) of 50% VO2peak for 60 minutes, 4 days a week; high-intensity, low-volume aerobic exercise (HI:LO) of 70% VO2peak for 45 minutes 3 days a week; and low- to moderate-intensity, low-volume aerobic exercise (LO:LO) of 50% VO2peak for 45 minutes 3 days per week.
The investigators used magnetic resonance imaging and proton magnetic resonance spectroscopy to analyze VAT and liver fat. The study participants (n = 36) were primarily women; the study included only 17 men.
Liver fat reduced by 2.62% ± 1.00% in the LO:HI group, by 2.38% ± 0.73% in the HI:LO group, and by 0.84% ± 0.47% in the LO:LO group. Liver fat increased in the placebo group by 1.10% ± 0.62% (P = .04).
Although the reductions in liver fat and VAT were small in the experimental groups, they were potentially clinically important. The investigators note, however, that exercise had no effect on levels of aminotransferases.
Patients who are obese have increased cardiometabolic risk relative to the normal-weight population. Excess visceral and liver adipose tissue are known to be independently associated with cardiometabolic risk in this patient population. Despite this knowledge, however, there are no exercise guidelines targeted at VAT or liver fat.
Although the current study was not powered to recommend an "optimal" dose of aerobic exercise for improving liver fat, recommendations could be developed on the basis of results from this study and others, said Rohit Loomba, MD, from the University of California, San Diego, and Helena Cortez-Pinto, MD, PhD, from the Faculdade de Medicina in Lisbon, Portugal, in an accompanying editorial.
"In summary, based upon the review of the available evidence, we offer the following recommendations to the clinicians and the patients suffering from [nonalcoholic fatty liver disease (NAFLD)] or those who are at risk of NAFLD," they write. "There is good quality evidence to support that regular exercise is beneficial in reducing the risk of NAFLD. In addition, both aerobic and resistance training [regimens] are equally effective in reducing liver fat in individuals with NAFLD even in the absence of weight loss," they write.
Two coauthors report various financial relationships with Merck Sharp & Dohme, NHMRC, Amylin Corporation, the Egg Board, NovoNordisk, Servier Laboratories, Pfizer, and iNova pharmaceuticals. The remaining authors, Dr Loomba, and Dr Cortez-Pinto have disclosed no relevant financial relationships.
J Hepatol. Published online April 7, 2015. Article abstract, Editorial full text
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