High-Intensity Aerobic Exercise Improves Both Hepatic Fat Content and Stiffness in Sedentary Obese Men with Nonalcoholic Fatty Liver Disease

Abstract

We compared the effects of 12-week programs of resistance training (RT), high-intensity interval aerobic training (HIAT), and moderate-intensity continuous aerobic training (MICT). The primary goal was to evaluate the therapeutic effects of the exercise modalities for the management of nonalcoholic fatty liver disease (NAFLD). A total of 61 sedentary obese men with NAFLD were randomized into one of the following exercise regimens (RT, HIAT, or MICT). Hepatic fat content was decreased to a similar extent in the RT, HIAT, and MICT groups (−14.3% vs. −13.7% vs. −14.3%) without significant changes in weight and visceral fat. The gene expression levels of fatty acid synthesis were significantly decreased in the subjects’ monocytes. Hepatic stiffness was decreased only in the HIAT group (−16.8%). The stiffness change was associated with restored Kupffer cell phagocytic function (+17.8%) and decreased levels of inflammation such as leptin (−13.2%) and ferritin (−14.1%). RT, HIAT, and MICT were equally effective in reducing hepatic fat content, but only HIAT was effective in improving hepatic stiffness and restoring Kupffer cell function. These benefits appeared to be independent of detectable weight and visceral fat reductions; the benefits were acquired through the modulation of in vivo fatty acid metabolism and obesity-related inflammatory conditions.

Exercise Training as Treatment of Nonalcoholic Fatty Liver Disease

“…Nine randomized control trials and four uncontrolled studies have investigated the effects of aerobic training in NAFLD (Table 1) [9][10][11][19][20][21][22][23][24][25][26][27][28]. All of the studies included at least one aerobic training experimental group, with three studies containing multiple aerobic training groups of differing exercise intensities [11,22,24].…”

“…Maximum heart rate (MHR), heart rate reserve (HRR), maximal predicted heart rate (MPHR), metabolic equivalent of task (MET), or VO 2max were used to determine exercise intensity prescriptions-where intensities range from light to moderate (30-39% of HRR, 57-63% of HRR, 2.0-3.9 METs, and 37-45% of VO 2max ) moderate (40-59% of HRR, 64-76% of HRR, 4.0-5.9 METs, and 46-63% of VO 2max ), and vigorous (60-89% of HRR, 77-95% of HRR, 6.0-8.4 METs, and 64-90% of VO 2max ) [9][10][11][19][20][21][22]24,26,27,29]. Exercise modalities included recreational walking, treadmill running, cycle ergometry, cross-training, rowing, and rhythmic exercise [10,11,[20][21][22][23][24][25][26][27]. Six studies used single modality exercise, while four studies used a multitude of exercise modalities [9][10][11][20][21][22][23][25][26][27].…”

“…Exercise modalities included recreational walking, treadmill running, cycle ergometry, cross-training, rowing, and rhythmic exercise [10,11,[20][21][22][23][24][25][26][27]. Six studies used single modality exercise, while four studies used a multitude of exercise modalities [9][10][11][20][21][22][23][25][26][27]. Only two studies did not specify aerobic training.…”

“…Although liver enzymes are insensitive markers of liver injury in NASH, a decrease in liver aminotransferases with treatment interventions may correlate histologic improvement in liver injury [31,32]. Overall, aerobic training reduces both systemic levels of ALT and AST [9][10][11]19,25,27,28]. Shamsoddini et al showed that moderate-intensity treadmill running significantly improved mean ALT from 36.9 ± 16.4 U/L to 24.4 ± 7.2 U/L, p = 0.002; and improved AST from 29.7 ± 9.0 U/L to 20.9 ± 4.4 U/L, p = 0.02 in an eight-week aerobic training intervention in 10 ultrasound-confirmed NAFLD patients [10].…”

“…While weight loss has remained fundamental to disease management, the benefits of exercise extend beyond weight loss alone. Exercise improves NAFLD independent of weight loss, however, the optimal exercise dose and pathophysiologic mechanisms by which exercise confers improvement in NAFLD remains unknown [9][10][11][12]. The practice guidelines for the management of NAFLD of the American Association for the Study of Liver Diseases (AASLD) recommends exercise; however, no specific approach or duration of exercise is otherwise detailed for practitioners [13].…”