August/September 2021 Issue
Focus on Fitness: Exercise for Fatty Liver Disease
By Jennifer Van Pelt, MA
Vol. 23, No. 7, P. 54
Metabolic-associated fatty liver disease (MAFLD) was recently introduced as a new name for nonalcoholic fatty liver disease by an international expert consensus panel to reflect its causes more accurately and eliminate its prominent association with alcohol use. With a global prevalence of approximately 25%, MAFLD is the leading cause of chronic liver disease worldwide.1,2
In MAFLD, fat accumulates in the liver cells, which, when healthy, should contain little or no fat. When imaging, biopsy, or blood biomarkers indicate fat build-up in the liver, and the individual also has overweight or obesity, type 2 diabetes, or other signs of metabolic dysfunction (eg, high waist circumference, hypertension, prediabetes, insulin resistance), MAFLD is diagnosed. There may or may not be symptoms of MAFLD until its later stages, when it progresses to liver fibrosis or cirrhosis.2
The increasing prevalence of MAFLD correlates with growing rates of obesity and metabolic syndrome. There are no pharmacological treatments specifically for MAFLD, though pharmaceuticals for treating underlying metabolic conditions may help indirectly. Dietary and exercise modifications are considered first-line treatments for MAFLD. Most guidelines don’t mention specific dietary patterns, other than decreasing sugar intake and avoiding processed foods; European guidelines do suggest following a Mediterranean diet. All guidelines recommend that those with MAFLD lose 7% to 10% of their body weight through a combination of diet modifications and moderate-intensity exercise.3 However, the frequency, type, and duration of exercise aren’t specified.
Research has shown that regular exercise combats the development and progression of metabolic conditions, such as type 2 diabetes, obesity, insulin resistance, and metabolic syndrome, that contribute to MAFLD. An April 2021 systematic review and meta-analysis of 15 randomized controlled trials evaluated the benefits of regular aerobic exercise in a total of 740 adults with MAFLD. Exercise interventions in the randomized controlled trials included continuous aerobic exercise of low or moderate intensity, combined aerobic and resistance training, and high-intensity interval training, performed for four to 24 weeks. Exercise session studies ranged from 30 minutes performed three days per week to 60 minutes performed seven days per week. Treadmill or stationary cycling were the most commonly used aerobic exercises in most studies.2
The meta-analysis found that both continuous and interval aerobic exercise significantly improved blood levels of alanine aminotransferase, a liver enzyme used to track liver damage, within 12 weeks. All categories of aerobic exercise—continuous, interval, and combination—were associated with improved intrahepatic triglycerides and reduced weight and BMI. The analysis didn’t find any difference between aerobic exercise intensities or weekly frequencies in reducing measures of MAFLD.2
Resistance training also has been researched for MAFLD, though not as thoroughly as aerobic exercise. A January 2017 systematic review and meta-analysis compared resistance training vs aerobic exercise for MAFLD. The researchers analyzed 24 studies of aerobic exercise and seven studies of resistance exercise in adults with MAFLD. Their analysis found that both aerobic and resistance exercise reduced fat accumulation associated with MAFLD when performed at similar frequency and duration; in the analyzed studies, average exercise time was 40 to 45 minutes per session, three times weekly for 12 weeks. No significant differences occurred in BMI nor blood levels of liver enzymes or lipids between the two types of exercises, leading the researchers to conclude that both improved MAFLD.4
The researchers also assessed measures of energy consumption and found that the energy and oxygen used was lower in those performing resistance exercise. The exact physiological mechanisms by which exercise improves MAFLD aren’t yet fully understood. Given the difference in energy requirements revealed by their analysis, the researchers speculated that resistance training and aerobic exercise may improve liver health through different mechanisms in the body. The suggested muscle activation and/or lipid metabolism may play a role during resistance training and cardiorespiratory exertion during aerobic exercise. They concluded that because many individuals with MAFLD have severe obesity, are older adults, or have mobility-limiting conditions, resistance training may be more appropriate as an exercise regimen because it requires less energy and cardiorespiratory exertion than aerobic exercise, which may be challenging for some of these individuals.4
Research also has shown that MAFLD increases cardiovascular morbidity and mortality, yet a lack of widespread awareness of the condition in the primary care setting has resulted in underdiagnosis in early stages, when dietary and exercise interventions are most beneficial.3
Nutrition professionals can facilitate awareness and improve diagnosis of MAFLD by encouraging clients with risk factors and associated metabolic conditions to inquire about testing with their primary care providers. And they can help clients with MAFLD integrate dietary and exercise interventions with physical abilities and exercise preferences to ensure long-term success. The following are practice tips for RDs:
• Help clients identify aerobic exercise they can perform, enjoy, and access. Gym memberships and cardiovascular equipment may not be ideal or affordable for all clients. Walking, inexpensive online or DVD low-impact exercise programs, and dancing can be performed more easily at home.
• Encourage clients with physical limitations to do what they can. For example, chair exercise programs incorporate both aerobic and resistance exercise and can be performed seated or with support when standing. For clients with mobility limitations and access to a pool, water exercise is an excellent option.
• Acknowledge that not all clients will be capable of performing aerobic exercise right away. Starting with resistance training with bands or light handheld weights, with exercises for all major muscle groups, appears to be as beneficial as aerobic exercise for improving MAFLD.
• Encourage clients who are physically able to try high-intensity interval training. Benefits can be achieved in less time, which may appeal to those with busy lifestyles. And high intensity doesn’t have to mean high impact. Intensity refers to the heart rate and level of exertion, which can be achieved with low-impact movements, and alternating intervals of resistance training with weights and low-impact aerobic exercise.
A February 2021 study of engagement with exercise in those with MAFLD highlighted that individuals with the condition were less aware of recommended weekly exercise guidelines and less likely to exercise regularly. Study participants indicated that lack of time, energy, and willpower/motivation were the most common barriers to exercising regularly to manage their MAFLD.5 Nutrition professionals are uniquely positioned to positively impact the management of MAFLD through effective dietary and exercise counseling.
— Jennifer Van Pelt, MA, is a certified group fitness instructor and health care researcher in the Lancaster, Pennsylvania, area.
1. Eslam M, Sanyal AJ, George J; International Consensus Panel. MAFLD: a consensus-driven proposed nomenclature for metabolic associated fatty liver disease. Gastroenterology. 2020;158(7):1999-2014.e1.
2. Słomko J, Zalewska M, Niemiro W, et al. Evidence-based aerobic exercise training in metabolic-associated fatty liver disease: systematic review with meta-analysis. J Clin Med. 2021;10(8):1659.
3. Ando Y, Jou JH. Nonalcoholic fatty liver disease and recent guideline updates. Clin Liver Dis (Hoboken). 2021;17(1):23-28.
4. Hashida R, Kawaguchi T, Bekki M, et al. Aerobic vs. resistance exercise in non-alcoholic fatty liver disease: a systematic review. J Hepatol. 2017;66(1):142-152.
5. O'Gorman P, Monaghan A, McGrath M, Naimimohasses S, Gormley J, Norris S. Determinants of physical activity engagement in patients with nonalcoholic fatty liver disease: the need for an individualized approach to lifestyle interventions. Phys Ther. 2021;101(2):pzaa195.