“In short duration studies, lifestyle changes that have focused on diet and exercise modification have shown promise in decreasing liver fat as a manifestation of early disease in [non-alcoholic fatty liver disease]. However, guidelines from specialist societies regarding recommendations for amounts and intensity of exercise/physical activity in NAFLD are variable,” Ki-Chul Sung, MD, PhD, from the division of cardiology and department of medicine at Kangbuk Samsung Hospital and Sungkyunkwan University School of Medicine, Seoul, Republic of Korea, and colleagues wrote. “Thus, at present it is unclear how much exercise is needed or how intense that exercise should be to prevent development of new fatty liver or to resolve existing fatty liver. We have utilized a retrospective study design of an occupational cohort … to assess relationships between exercise and change in fatty liver status over time.”

The adequate intensity and duration of exercise needed to target liver fat is still uncertain; therefore, Sung and colleagues aimed to determine the baseline amount of exercise that would be associated with inhibited development of new liver fat and resolution of baseline liver fat at a five-year follow up.

To assess the relationship between exercise and incident fatty liver, as well as exercise and resolution of existing fatty liver, the researchers gathered data from the Kangbuk Samsung Health Study. This cohort study consisted of men and women aged 18 years or older, and contained data from annual and biennial health screenings. Participants provided information on alcohol consumption, education and smoking history, which was evaluated against frequency of moderate or vigorous physical activity. To gauge their level of physical fitness, the participants were asked how many days per week they undertook physical activity, levels of perspiration and time spent on exercise sessions.

Taking height, body weight, and BMI into account, the researchers conducted statistical analyses using STATA version 11.2 and determined the HRs for incident fatty liver and resolution of fatty liver.

The study included 233,676 participants who were screened between 2002 and 2014. Of these participants, 126,811 were identified without fatty liver, yet 29,014 developed incident fatty liver during follow-up. Among those who did have liver fat, 42,536 had liver fat at baseline, 14,514 of whom experienced resolution of liver fat during follow-up.

Exercise was associated with reducing development of fatty liver and resolving existing fatty liver. For those who exercised at least 5 times per week, the HR for incident fatty liver was 0.86 (95% CI, 0.8-0.92; P < .001), and the HR for resolution of fatty liver was 1.4 (95% CI, 1.25-1.55; P < .001). Overall, there was a distinct association between exercise and reduction of fatty liver and resolution of fatty liver during follow-up.

“The novel results of our study are that any amount exercise is beneficial in either decreasing risk of development of new fatty liver, or in improving resolution of existing fatty liver, over 5 years of follow-up,” Sung and colleagues wrote. “During follow up, any increase in the number of weekly exercise sessions was associated with both a decrease in risk of incident fatty liver and resolution of existing fatty liver, and these associations were independent of any change in BMI during the period of follow-up.” – by Rafi Naseer