Aerobic capacity and exercise performance in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is one of the leading causes of chronic liver disease worldwide. Exercise has proven effective in treating NAFLD, and many clinical initiatives seek to increase uptake of exercise in this population. This study aimed to elucidate the physiological responses of individuals with NAFLD to graded exercise testing.

Seventeen participants with presumed NAFLD and 15 without were assessed through symptom-limited, Modified Bruce treadmill testing. Gas exchange, impedance cardiometry, and perceived exertion ratings were used to assess exercise performance, response and perception. Patient-self reports were also obtained.

Individuals with NAFLD were older (49.00 [38.50, 54.50] vs. 30.00[22.00, 42.00] years, P=0.018) with higher Body Mass Index (32.54[27.38, 34.98] vs. 25.62[23.76, 30.72], P=0.012), but demonstrated no other differences with regards to sex, race, blood pressure, resting heart rate, or habitual activity. Individuals demonstrated no between-group differences in total exercise time, anaerobic threshold (AT) onset time, or cardiac output. While individuals with NAFLD displayed a decreased peak oxygen consumption (VO2) (25.70[23.60, 27.20] vs. 31.00[26.00, 42.70], P=0.036) relative to controls, a similar difference was not found for the percentage of predicted VO2max achieved, suggesting that NAFLD may not impair exercise physiology beyond what is observed in obese individuals.

Exercise capacity appears preserved in participants with NAFLD relative to their control counterparts. Peak VO2 is reduced among these patients, suggesting impaired aerobic capacity. Future studies may seek to determine whether this finding is directly related to the diagnosis of NAFLD, or more generally to states of obesity and physical deconditioning.