The Effect of High-intensity Interval Training vs Moderate-intensity Continuous Training on Liver Fat: A Systematic Review and Meta-Analysis

High-intensity interval training for cardiometabolic health in adults with metabolic syndrome: a systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

To assess the effectiveness of high-intensity interval training (HIIT) compared with traditional moderate-intensity continuous training (MICT) and/or non-exercise control (CON) for modification of metabolic syndrome (MetS) components and other cardiometabolic health outcomes in individuals with MetS.

DESIGN

Systematic review and meta-analysis DATA SOURCES: Five databases were searched from inception to March 2024.

STUDY APPRAISAL AND SYNTHESIS

Meta-analyses of randomised controlled trials (RCTs) comparing HIIT with MICT/CON were performed for components of MetS (waist circumference (WC), systolic blood pressure (SBP), diastolic blood pressure (DBP), high-density lipoprotein cholesterol (HDL-C), triglyceride (TG), and fasting blood glucose (BG)) and clinically relevant cardiometabolic health parameters. Subgroup moderator analyses were conducted based on the intervention duration and HIIT volume.

RESULTS

Out of 4819 studies, 23 RCTs involving 1374 participants were included (mean age: 46.2-67.0 years, 55% male). HIIT significantly improved WC (weighted mean difference (WMD) -4.12 cm, 95% CI -4.71 to -3.53), SBP (WMD -6.05 mm Hg, 95% CI -8.11 to -4.00), DBP (WMD -3.68 mm Hg, 95% CI -5.70 to -1.65), HDL-C (WMD 0.12 mmol/L, 95% CI 0.04 to 0.20), TG (WMD -0.34 mmol/L, 95% CI -0.41 to -0.27) and BG (WMD -0.35 mmol/L, 95% CI -0.54 to -0.16) compared with CON (all p<0.01). HIIT approaches demonstrated comparable effects to MICT across all parameters. Subgroup analyses suggested that HIIT protocols with low volume (ie, <15 min of high-intensity exercise per session) were not inferior to higher volume protocols for improving MetS components.

CONCLUSION

This review supports HIIT as an efficacious exercise strategy for improving cardiometabolic health in individuals with MetS. Low-volume HIIT appears to be a viable alternative to traditional forms of aerobic exercise.

Exercise-promoted adiponectin secretion activates autolysosomes to protect the liver of ApoE-/- mice from a high-fat diet

Fat is a "double-edged sword": while it is a necessary substance for the body, the long-term intake of excessive fat will cause obesity, with the liver subjected to lipotoxicity as it accumulates. It will then continue to deteriorate, eventually leading to liver failure, which is a negative impact of high-fat food intake. Research has shown that exercise can reverse the side effects of a chronic high-fat diet and help the body to mitigate the harmful effects of lipotoxicity. In our study, it was found that moderate-intensity cardio-training (MICT) and high-intensity interval exercise (HIIT) effectively protected the livers of high-fat diet (HFD) ApoE-/- mice against lipotoxicity. Previous results demonstrated that 12 weeks of HFD resulted in a significant elevation of CD36 in the livers of C57BL/6J mice, while knockdown of CD36 did not reduce the accumulation of fat in the liver. Therefore, we used ApoE-/- mice as experimental subjects. Although HFD caused the development of hyperlipidemia and atherosclerosis, it is interesting to note that, due to the knockdown of ApoE, the livers of ApoE-/- mice in the non-exercise group did not show significant lipid deposition; however, after 12 weeks of MICT and HIIT, the livers of ApoE-/- mice showed significant lipid deposition. After we analyzed the lipid metabolism in their livers, we found that this was caused by the promotion of transport of peripheral fat into the liver due to exercise. Moreover, 12 weeks of exercise effectively reduced atherosclerosis, and the livers of ApoE-/- mice in the exercise group were not damaged by lipotoxicity. The results showed that a 12-week exercise treatment activated AMPK in the livers of HFD ApoE-/- mice through the APN-AdipoR1 signaling pathway, improved hepatic lipid metabolism disorders, and promoted the nuclear translocation of TFEB to enhance autophagic-lysosomal lipid scavenging. After the peripheral lipid is input into the liver due to exercise, the energy generated through gluconeogenesis can be used to replenish the energy consumed by exercise and maintain the normal operation of various functions in the liver, based on which the high autophagic flux in the liver can be maintained and the lipid clearance rate can be enhanced to protect the liver from lipotoxicity.

The Release of Lipolytic Hormones during Various High-Intensity Interval and Moderate-Intensity Continuous Training Regimens and Their Effects on Fat Loss

To investigate the release of lipolytic hormones during various high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT), and their effects on fat loss. 39 young women categorized as obese (with a body fat percentage (BFP) ≥30%) were randomly allocated to one of the following groups: all-out sprint interval training (SIT, n =10); supramaximal HIIT (HIIT120, 120%V̇O2peak, n = 10); HIIT (HIIT90, 90%V̇O2peak, n = 10), or MICT, (60%V̇O2peak, n = 9) for a twelve-week observation period consisting of 3 to 4 exercise sessions per week. Serum epinephrine (EPI) and growth hormone (GH) were measured during the 1st, 20th, and 44th training sessions. Body weight (BW), body mass index (BMI), whole-body fat mass (FM) and BFP were assessed pre- and post-intervention. Following the 1st and 20th sessions, significant increases in EPI (p < 0.05) were observed post-exercise in HIIT120 and HIIT90, but not in SIT and MICT. In the 44th session, the increased EPI was found in SIT, HIIT120, and HIIT90, but not in MICT (p < 0.05). For the GH, a significant increase was observed post-exercise in all groups in the three sessions. The increased EPI and GH returned to baselines 3 hours post-exercise. After the 12-week intervention, significant reductions in FM and BFP were found in all groups, while reductions in BW and BMI were only found in the SIT and HIIT groups. Greater reductions in FM and BFP, in comparison to MICT, were observed in the SIT and HIIT groups (p < 0.05). 12-week SIT, HIIT120, and HIIT90, in comparison to MICT, were more efficacious in fat reduction in obese women, partly benefiting from the greater release of lipolytic hormones during training sessions.

Exercise improves surrogate measures of liver histological response in metabolic dysfunction-associated steatotic liver disease

BACKGROUND AND AIMS

Exercise is recommended for the management of metabolic dysfunction-associated steatotic liver disease (MASLD), yet effects on liver histology remain unknown, especially without significant weight loss. We aimed to examine changes in surrogate measures of liver histological response with exercise training.

METHODS

We conducted a post hoc pooled analysis of three randomised controlled trials (duration: 12-20 weeks) comparing aerobic exercise interventions with controls. The primary outcome measure was a ≥30% relative reduction in (MRI-measured) liver fat, as a surrogate measure of liver histological response (the threshold necessary for fibrosis improvement). Secondary outcome measures were changes in other biomarkers of liver fibrosis, anthropometry, body composition and aerobic fitness.

RESULTS

Eighty-eight adults (exercise: 54, control: 34; male: 67%) were included with mean (SD) age 51 (11) years and body mass index 33.3 (5.2) kg/m2. Following the intervention, exercise had ~5-fold (OR [95%CI]: 4.86 [1.72, 13.8], p = .002) greater odds of ≥30% relative reduction in MRI-measured liver fat compared with control. This paralleled the improvements in anthropometry (waist and hip circumference reduction), body composition (body fat, visceral and subcutaneous adipose tissue) and aerobic fitness (V̇O2peak, ventilatory threshold and exercise capacity). Importantly, these effects were independent of clinically significant body weight loss (<3% body weight).

CONCLUSION

Exercise training led to clinically meaningful improvements in surrogate serum- and imaging-based measures of liver histological change, without clinically meaningful body weight reduction. These data reinforce the weight-neutral benefit of exercise training and suggest that aerobic training may improve liver fibrosis in patients with MASLD.

EASL-EASD-EASO Clinical Practice Guidelines on the management of metabolic dysfunction-associated steatotic liver disease (MASLD)

Metabolic dysfunction-associated steatotic liver disease (MASLD), previously termed non-alcoholic fatty liver disease (NAFLD), is defined as steatotic liver disease (SLD) in the presence of one or more cardiometabolic risk factor(s) and the absence of harmful alcohol intake. The spectrum of MASLD includes steatosis, metabolic dysfunction-associated steatohepatitis (MASH, previously NASH), fibrosis, cirrhosis and MASH-related hepatocellular carcinoma (HCC). This joint EASL-EASD-EASO guideline provides an update on definitions, prevention, screening, diagnosis and treatment for MASLD. Case-finding strategies for MASLD with liver fibrosis, using non-invasive tests, should be applied in individuals with cardiometabolic risk factors, abnormal liver enzymes, and/or radiological signs of hepatic steatosis, particularly in the presence of type 2 diabetes (T2D) or obesity with additional metabolic risk factor(s). A stepwise approach using blood-based scores (such as FIB-4) and, sequentially, imaging techniques (such as transient elastography) is suitable to rule-out/in advanced fibrosis, which is predictive of liver-related outcomes. In adults with MASLD, lifestyle modification - including weight loss, dietary changes, physical exercise and discouraging alcohol consumption - as well as optimal management of comorbidities - including use of incretin-based therapies (e.g. semaglutide, tirzepatide) for T2D or obesity, if indicated - is advised. Bariatric surgery is also an option in individuals with MASLD and obesity. If locally approved and dependent on the label, adults with non-cirrhotic MASH and significant liver fibrosis (stage ≥2) should be considered for a MASH-targeted treatment with resmetirom, which demonstrated histological effectiveness on steatohepatitis and fibrosis with an acceptable safety and tolerability profile. No MASH-targeted pharmacotherapy can currently be recommended for the cirrhotic stage. Management of MASH-related cirrhosis includes adaptations of metabolic drugs, nutritional counselling, surveillance for portal hypertension and HCC, as well as liver transplantation in decompensated cirrhosis.

High-intensity interval training improves hypothalamic inflammation by suppressing HIF-1α signaling in microglia of male C57BL/6J mice

Repeated bouts of high-intensity interval training (HIIT) induce an improvement in metabolism via plasticity of melanocortin circuits and attenuated hypothalamic inflammation. HIF-1α, which plays a vital role in hypothalamus-mediated regulation of peripheral metabolism, is enhanced in the hypothalamus by HIIT. This study aimed to investigate the effects of HIIT on hypothalamic HIF-1α expression and peripheral metabolism in obese mice and the underlying molecular mechanisms. By using a high-fat diet (HFD)-induced obesity mouse model, we determined the effect of HIIT on energy balance and the expression of the hypothalamic appetite-regulating neuropeptides, POMC and NPY. Moreover, hypothalamic HIF-1α signaling and its downstream glycolytic enzymes were explored after HIIT intervention. The state of microglia and microglial NF-κB signaling in the hypothalamus were also examined in vivo. In vitro by using an adenovirus carrying shRNA-HIF1β, we explored the impact of HIF-1 signaling on glycolysis and NF-κB inflammatory signaling in BV2 cells. Food intake was suppressed and whole-body metabolism was improved in exercised DIO mice, accompanied by changes in the expression of POMC and NPY. Moreover, total and microglial HIF-1α signaling were obviously attenuated in the hypothalamus, consistent with the decreased levels of glycolytic enzymes. Both HFD-induced microglial activation and hypothalamic NF-κB signaling were significantly suppressed following HIIT in vivo. In BV2 cells, after HIF-1 complex knockdown, glycolysis and NF-κB inflammatory signaling were significantly attenuated. The data indicate that HIIT improves peripheral metabolism probably via attenuated HFD-induced microglial activation and microglial NF-κB signaling in the hypothalamus, which could be mediated by suppressed microglial HIF-1α signaling.

Histological improvements following energy restriction and exercise: The role of insulin resistance in resolution of MASH

BACKGROUND & AIMS

Metabolic-dysfunction associated steatohepatitis (MASH) is one of the most common liver diseases worldwide and is characterized by multi-tissue insulin resistance. The effects of a 10-month energy restriction and exercise intervention on liver histology, anthropometrics, plasma biochemistries, and insulin sensitivity were compared to standard of care (control) to understand mechanisms that support liver health improvements.

METHODS

Following medical diagnosis of MASH, subjects were randomized to treatment (n=16) or control (n=8). Liver fat (MRS), 18-hour plasma biochemical measurements, and isotopically-labeled hyperinsulinemic-euglycemic clamps were completed pre- and post-intervention. Body composition and cardiorespiratory fitness (VO2peak) were also measured mid-intervention. Treatment subjects were counseled to reduce energy intake and completed supervised, high-intensity interval training (3x/week) for 10 months. Control subjects continued physician-directed care.

RESULTS

Treatment induced significant (P<0.05) reductions in body weight, fat mass, and liver injury, while VO2peak (P<0.05) and fatty acid (NEFA) suppression (P=0.06) were improved. Both groups exhibited reductions in total energy intake, HbA1c, hepatic insulin resistance, and liver fat (P<0.05). Compared to control, treatment induced a two-fold increase in peripheral insulin sensitivity which was significantly related to higher VO2peak and resolution of liver disease, despite no group differences in peripheral insulin sensitivity.

CONCLUSIONS

Exercise and energy-restriction elicited significant and clinically-meaningful treatment effects on liver health, potentially driven by a redistribution of excess nutrients to skeletal muscle, thereby reducing hepatic nutrient toxicity. Clinical guidelines should emphasize the addition of aerobic exercise in lifestyle treatments for the greatest histologic benefit in individuals with advanced MASH.

CLINICAL TRIAL NUMBER

NCT03151798.

EASL-EASD-EASO Clinical Practice Guidelines on the Management of Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD)

Metabolic dysfunction-associated steatotic liver disease (MASLD), previously termed non-alcoholic fatty liver disease (NAFLD), is defined as steatotic liver disease (SLD) in the presence of one or more cardiometabolic risk factor(s) and the absence of harmful alcohol intake. The spectrum of MASLD includes steatosis, metabolic dysfunction-associated steatohepatitis (MASH, previously NASH), fibrosis, cirrhosis and MASH-related hepatocellular carcinoma (HCC). This joint EASL-EASD-EASO guideline provides an update on definitions, prevention, screening, diagnosis and treatment for MASLD. Case-finding strategies for MASLD with liver fibrosis, using non-invasive tests, should be applied in individuals with cardiometabolic risk factors, abnormal liver enzymes, and/or radiological signs of hepatic steatosis, particularly in the presence of type 2 diabetes (T2D) or obesity with additional metabolic risk factor(s). A stepwise approach using blood-based scores (such as FIB-4) and, sequentially, imaging techniques (such as transient elastography) is suitable to rule-out/in advanced fibrosis, which is predictive of liver-related outcomes. In adults with MASLD, lifestyle modification - including weight loss, dietary changes, physical exercise and discouraging alcohol consumption - as well as optimal management of comorbidities - including use of incretin-based therapies (e.g. semaglutide, tirzepatide) for T2D or obesity, if indicated - is advised. Bariatric surgery is also an option in individuals with MASLD and obesity. If locally approved and dependent on the label, adults with non-cirrhotic MASH and significant liver fibrosis (stage ≥2) should be considered for a MASH-targeted treatment with resmetirom, which demonstrated histological effectiveness on steatohepatitis and fibrosis with an acceptable safety and tolerability profile. No MASH-targeted pharmacotherapy can currently be recommended for the cirrhotic stage. Management of MASH-related cirrhosis includes adaptations of metabolic drugs, nutritional counselling, surveillance for portal hypertension and HCC, as well as liver transplantation in decompensated cirrhosis.

Progress and hotspot of diet or exercise therapy in the treatment of non-alcoholic fatty liver disease

Introduction

The primary treatment for non-alcoholic fatty liver disease (NAFLD) is modifying lifestyle through dietary or exercise interventions. In recent decades, it has received increasing attention. However, the lack of bibliometric analysis has posed a challenge for researchers seeking to understand the overall trends in this field.

Methods

As of February 3rd, 2024, 876 articles on treating NAFLD through diet or exercise therapy from 2013 to 2023 had been retrieved. Two software tools, VOSviewer and CiteSpace, were utilized to analyze the growth of publications, countries, institutions, authors, journals, citations, and keywords. Additionally, the keywords with strong citation burstiness were identified to determine the changes and future trends of research hotspots in this field.

Results

China had the highest number of articles, followed by the United States and South Korea. Yonsei University and Nutrients were the institutions and journals with the most significant contributions. Professor Younossi Zobair M, from the United States, is the most prolific author in this field. Through analyzing the keywords, three research hotspots were identified: research on the pathogenesis of NAFLD, research on the treatment modalities of NAFLD, and research on the risk factors and diagnosis methods of NAFLD. In recent years, the research emphasis in this field has changed, suggesting that future research will focus on two frontier keywords: "oxidative stress" and "aerobic capacity."

Conclusion

In the past eleven years, the attention in this field was still rising, and the authors, journals, countries and so on had formed a considerable cooperative relationship. There were also many highly influential and productive researchers in this field. It is speculated that new research will continue around "aerobic exercise" and "oxidative stress" in the future.

A systematic review and cluster analysis approach of 103 studies of high-intensity interval training on cardiorespiratory fitness

AIMS

This study aims to systematically review the systematic reviews and meta-analyses examining the effect of high-intensity interval training (HIIT) protocols on improving cardiorespiratory fitness (CRF) and to characterize the main patterns of HIIT modalities using clustering statistical procedures to examine their potential differences on improving CRF. Finally, we aimed to develop a comprehensive guideline for reporting HIIT protocols.

METHODS AND RESULTS

A systematic review was conducted on PubMed and Web of Science from their inception to 31 October 2022 for systematic reviews and meta-analysis aimed at assessing the effect of HIIT on CRF in the entire study population. The Assessment of Multiple Systematic Reviews 2 tool was used to evaluate the risk of bias of each review. Additionally, a principal component analysis testing the data adequacy for the factor solution through the Kaiser-Meyer-Olkin procedure test was conducted. Once the number of factors was identified, in order to identify data patterns according to the main characteristics of the HIIT protocols, a two-step cluster analysis was conducted. Nineteen systematic reviews and/or meta-analyses comprising 103 studies were included. Clustering of systematic reviews and meta-analyses identified three HIIT modalities ('HIIT-normal mixed', 'HIIT-long running', and 'HIIT-short cycling') underlying the interventions across the included studies. Similar effectiveness in increasing CRF among the three HIIT modalities was observed. Subgroup analyses showed no significant differences in CRF by sex, weight status, study design, and baseline physical activity level (P > 0.05), but differences were observed by age group, and exercise intensity indicator was used in the HIIT programmes (P < 0.05).

CONCLUSION

All three HIIT modalities produced significant improvements of CRF, although some modalities showed greater changes for some specific age groups or intensity indicators.

Exercise in the Management of Metabolic-Associated Fatty Liver Disease (MAFLD) in Adults: A Position Statement from Exercise and Sport Science Australia

Metabolic-associated fatty liver disease (MAFLD) is the most prevalent chronic liver disease worldwide, affecting 25% of people globally and up to 80% of people with obesity. MAFLD is characterised by fat accumulation in the liver (hepatic steatosis) with varying degrees of inflammation and fibrosis. MAFLD is strongly linked with cardiometabolic disease and lifestyle-related cancers, in addition to heightened liver-related morbidity and mortality. This position statement examines evidence for exercise in the management of MAFLD and describes the role of the exercise professional in the context of the multi-disciplinary care team. The purpose of these guidelines is to equip the exercise professional with a broad understanding of the pathophysiological underpinnings of MAFLD, how it is diagnosed and managed in clinical practice, and to provide evidence- and consensus-based recommendations for exercise therapy in MAFLD management. The majority of research evidence indicates that 150-240 min per week of at least moderate-intensity aerobic exercise can reduce hepatic steatosis by ~ 2-4% (absolute reduction), but as little as 135 min/week has been shown to be effective. While emerging evidence shows that high-intensity interval training (HIIT) approaches may provide comparable benefit on hepatic steatosis, there does not appear to be an intensity-dependent benefit, as long as the recommended exercise volume is achieved. This dose of exercise is likely to also reduce central adiposity, increase cardiorespiratory fitness and improve cardiometabolic health, irrespective of weight loss. Resistance training should be considered in addition to, and not instead of, aerobic exercise targets. The information in this statement is relevant and appropriate for people living with the condition historically termed non-alcoholic fatty liver disease (NAFLD), regardless of terminology.

Lifestyle interventions in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a dynamic chronic liver disease that develops in close association with metabolic irregularities. Between 2016 and 2019, the global prevalence among adults was reported as 38% and among children and adolescents it was about 10%. NAFLD can be progressive and is associated with increased mortality from cardiovascular disease, extrahepatic cancers and liver complications. Despite these numerous adverse outcomes, no pharmacological treatments currently exist to treat nonalcoholic steatohepatitis, the progressive form of NAFLD. Therefore, the main treatment is the pursuit of a healthy lifestyle for both children and adults, which includes a diet rich in fruits, nuts, seeds, whole grains, fish and chicken and avoiding overconsumption of ultra-processed food, red meat, sugar-sweetened beverages and foods cooked at high heat. Physical activity at a level where one can talk but not sing is also recommended, including leisure-time activities and structured exercise. Avoidance of smoking and alcohol is also recommended. Policy-makers, community and school leaders need to work together to make their environments healthy by developing walkable and safe spaces with food stores stocked with culturally appropriate and healthy food items at affordable prices as well as providing age-appropriate and safe play areas in both schools and neighbourhoods.

High-intensity Interval Training for the Management of Nonalcoholic Steatohepatitis: Participant Experiences and Perspectives

Background and Aims

High-intensity interval training (HIIT) is a therapeutic option for people with nonalcoholic steatohepatitis (NASH). However, the perspectives and experiences of HIIT for people with NASH are unknown, limiting translation of research. We explored the experiences and perspectives of both professionally supervised and self-directed HIIT in people with NASH and evaluated participant-reported knowledge, barriers, and enablers to commencing and sustaining HIIT.

Methods

Twelve participants with NASH underwent 12 weeks of supervised HIIT (3 days/week, 4×4 minutes at 85-95% maximal heart rate, interspersed with 3 minutes active recovery), followed by 12-weeks of self-directed (unsupervised) HIIT. One-on-one, semistructured participant interviews were conducted by exercise staff prior to HIIT and following both supervised and self-directed HIIT to explore prior knowledge, barriers, enablers, and outcomes at each stage. Interviews were audio-recorded, transcribed, coded, and thematically analyzed by two independent researchers.

Results

Four dominant themes were identified: (1) no awareness of/experience with HIIT and ambivalence about exercise capabilities; (2) multiple medical and social barriers to commencing and continuing HIIT; (3) exercise specialist support was a highly valued enabler, and (4) HIIT was enjoyed and provided holistic benefits.

Conclusions

People with NASH may lack knowledge of and confidence for HIIT, and experience multiple complex barriers to commencing and continuing HIIT. Exercise specialist support is a key enabler to sustained engagement. These factors need to be addressed in future clinical programs to augment the uptake and long-term sustainability of HIIT by people with NASH so they can experience the range of related benefits.

Physical Activity and Nonalcoholic Fatty Liver Disease: A Roundtable Statement from the American College of Sports Medicine

ABSTRACT

Although physical activity (PA) is crucial in the prevention and clinical management of nonalcoholic fatty liver disease, most individuals with this chronic disease are inactive and do not achieve recommended amounts of PA. There is a robust and consistent body of evidence highlighting the benefit of participating in regular PA, including a reduction in liver fat and improvement in body composition, cardiorespiratory fitness, vascular biology, and health-related quality of life. Importantly, the benefits of regular PA can be seen without clinically significant weight loss. At least 150 min of moderate or 75 min of vigorous intensity PA are recommended weekly for all patients with nonalcoholic fatty liver disease, including those with compensated cirrhosis. If a formal exercise training program is prescribed, aerobic exercise with the addition of resistance training is preferred. In this roundtable document, the benefits of PA are discussed, along with recommendations for 1) PA assessment and screening; 2) how best to advise, counsel, and prescribe regular PA; and 3) when to refer to an exercise specialist.

Exercise Training Is Associated With Treatment Response in Liver Fat Content by Magnetic Resonance Imaging Independent of Clinically Significant Body Weight Loss in Patients With Nonalcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis

INTRODUCTION

Exercise training is crucial in the management of nonalcoholic fatty liver disease (NAFLD); however, whether it can achieve clinically meaningful improvement in liver fat is unclear. We investigated the association between exercise training and the achievement of validated thresholds of MRI-measured treatment response.

METHODS

Randomized controlled trials in adults with NAFLD were identified through March 2022. Exercise training was compared with no exercise training. The primary outcome was ≥30% relative reduction in MRI-measured liver fat (threshold required for histologic improvement in nonalcoholic steatohepatitis activity, nonalcoholic steatohepatitis resolution, and liver fibrosis stage). Different exercise doses were compared.

RESULTS

Fourteen studies (551 subjects) met inclusion criteria (mean age 53.3 yrs; body mass index 31.1 kg/m 2 ). Exercise training subjects were more likely to achieve ≥30% relative reduction in MRI-measured liver fat (odds ratio 3.51, 95% confidence interval 1.49-8.23, P = 0.004) than those in the control condition. An exercise dose of ≥750 metabolic equivalents of task min/wk (e.g., 150 min/wk of brisk walking) resulted in significant treatment response (MRI response odds ratio 3.73, 95% confidence interval 1.34-10.41, P = 0.010), but lesser doses of exercise did not. Treatment response was independent of clinically significant body weight loss (>5%).

DISCUSSION

Independent of weight loss, exercise training is 3 and a half times more likely to achieve clinically meaningful treatment response in MRI-measured liver fat compared with standard clinical care. An exercise dose of at least 750 metabolic equivalents of task-min/wk seems required to achieve treatment response. These results further support the weight-neutral benefit of exercise in all patients with NAFLD.

Identifying Patients with Nonalcoholic Fatty Liver Disease in Primary Care: How and for What Benefit?

Despite its increasing prevalence, nonalcoholic fatty liver disease (NAFLD) remains under-diagnosed in primary care. Timely diagnosis is critical, as NAFLD can progress to nonalcoholic steatohepatitis, fibrosis, cirrhosis, hepatocellular carcinoma, and death; furthermore, NAFLD is also a risk factor linked to cardiometabolic outcomes. Identifying patients with NAFLD, and particularly those at risk of advanced fibrosis, is important so that healthcare practitioners can optimize care delivery in an effort to prevent disease progression. This review debates the practical issues that primary care physicians encounter when managing NAFLD, using a patient case study to illustrate the challenges and decisions that physicians face. It explores the pros and cons of different diagnostic strategies and tools that physicians can adopt in primary care settings, depending on how NAFLD presents and progresses. We discuss the importance of prescribing lifestyle changes to achieve weight loss and mitigate disease progression. A diagnostic and management flow chart is provided, showing the key points of assessment for primary care physicians. The advantages and disadvantages of advanced fibrosis risk assessments in primary care settings and the factors that influence patient referral to a hepatologist are also reviewed.

Exercise Is Medicine for Nonalcoholic Fatty Liver Disease: Exploration of Putative Mechanisms

Exercise remains a key component of nonalcoholic fatty liver disease (NAFLD) treatment. The mechanisms that underpin improvements in NAFLD remain the focus of much exploration in our attempt to better understand how exercise benefits patients with NAFLD. In this review, we summarize the available scientific literature in terms of mechanistic studies which explore the role of exercise training in modulating fatty acid metabolism, reducing hepatic inflammation, and improving liver fibrosis. This review highlights that beyond simple energy expenditure, the activation of key receptors and pathways may influence the degree of NAFLD-related improvements with some pathways being sensitive to exercise type, intensity, and volume. Importantly, each therapeutic target of exercise training in this review is also the focus of previous or ongoing drug development studies in patients with nonalcoholic steatohepatitis (NASH), and even when a regulatory-agency-approved drug comes to market, exercise will likely remain an integral component in the clinical management of patients with NAFLD and NASH.

Effect of Exercise on Liver Function and Insulin Resistance Markers in Patients with Non-Alcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Structured exercise as part of lifestyle modification plays an important role in the improvement of non-alcoholic fatty liver disease (NAFLD); however, its effectiveness has been shown to vary. This systematic review with meta-analysis investigated the effects of exercise on liver function and insulin resistance markers in patients with NAFLD.

METHODS

Six electronic databases were searched using terms related to exercise and NAFLD up to March 2022. Data were analyzed using a random-effects model to estimate the standardized mean difference (SMD) and 95% confidence interval.

RESULTS

The systematic search identified 2583 articles, of which a total of 26 studies met the inclusion criteria and were eligible. Exercise training had a moderate effect on reducing ALT (SMD: -0.59, p = 0.01) and small effects on reducing AST (SMD: -0.40, p = 0.01) and insulin (SMD: -0.43, p = 0.02). Significant reductions in ALT were found following aerobic training (SMD: -0.63, p < 0.01) and resistance training (SMD: -0.45, p < 0.001). Moreover, reductions in AST were found following resistance training (SMD: -0.54, p = 0.001), but not after aerobic training and combined training. However, reductions in insulin were found following aerobic training (SMD: -0.55, p = 0.03). Exercise interventions for <12 weeks compared to ≥12 weeks were more effective in reducing FBG and HOMA-IR, while interventions for ≥12 weeks compared to <12 weeks were more effective in reducing ALT and AST levels.

CONCLUSIONS

Our findings support the effectiveness of exercise in improving liver function markers but not in blood glucose control in NAFLD patients. Additional studies are needed to determine the exercise prescription to maximize health in these patients.

Advances in the Diagnosis and Treatment of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease that affects approximately one-quarter of the global adult population, posing a significant threat to human health with wide-ranging social and economic implications. The main characteristic of NAFLD is considered that the excessive fat is accumulated and deposited in hepatocytes without excess alcohol intake or some other pathological causes. NAFLD is a progressive disease, ranging from steatosis to non-alcoholic steatohepatitis (NASH), cirrhosis, hepatocellular carcinoma, liver transplantation, and death. Therefore, NAFLD will probably emerge as the leading cause of end-stage liver disease in the coming decades. Unlike other highly prevalent diseases, NAFLD has received little attention from the global public health community. Liver biopsy is currently considered the gold standard for the diagnosis and staging of NAFLD because of the absence of noninvasive and specific biomarkers. Due to the complex pathophysiological mechanisms of NAFLD and the heterogeneity of the disease phenotype, no specific pharmacological therapies have been approved for NAFLD at present, although several drugs are in advanced stages of development. This review summarizes the current evidence on the pathogenesis, diagnosis and treatment of NAFLD.

The independent effect of exercise on biopsy-proven non-alcoholic fatty liver disease: A systematic review

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide. Although previous studies have demonstrated that exercise independently reduces hepatic steatosis measured by imaging modalities in NAFLD, the effect of exercise on histological endpoints remains unclear. We aimed to conduct a systematic review of the independent effect of exercise on hepatic steatosis, steatohepatitis, and liver fibrosis as measured by histological assessment or non-invasive tests (NITs) in biopsy-proven NAFLD. A systematic literature search of PubMed, Embase, and Web of Science databases was performed using keywords related to exercise, NAFLD, and biopsy. Articles were selected based on the following inclusion criteria: (1) involved human subjects with biopsy-proven NAFLD, (2) analyzed the independent effect of exercise, (3) assessed changes in hepatic steatosis, steatohepatitis, or liver fibrosis via either histological evaluation or NITs, and (4) were original research studies. We identified a total of six studies that analyzed the independent effect of exercise on histological endpoints in biopsy-proven NAFLD. Two randomized controlled trials (RCTs) did not detect significant histological improvement following exercise interventions, while other non-randomized interventional studies showed that exercise reduces hepatocyte ballooning and liver fibrosis. In addition, five studies assessed NIT outcomes, collectively demonstrating that exercise improves hepatic steatosis measured by magnetic resonance imaging-based techniques but not serum biomarkers for steatohepatitis and liver fibrosis. Additional large RCTs and meta-analyses are warranted to investigate the independent effect of exercise on histological and clinical outcome endpoints in NAFLD.

The effect of 12 weeks of combined training on hepatic fat content and metabolic flexibility of individuals with non-alcoholic fatty liver disease: Protocol of an open-label, single-center randomized control trial

Introduction

Metabolic flexibility (MetF) is the capacity of an organism to oxidate substrate according to substrate availability or demand. The mismatch of substrate availability and oxidation may cause ectopic fat accumulation in the muscle and the liver. The objectives of the study are to examine the effect of 12 weeks of combined exercise on hepatic fat reduction and investigate metabolites related to MetF before and after the high-fat diet between individuals with NAFLD and healthy control with an active lifestyle.

Methods

This study is an open-label, single-center trial randomized controlled clinical study plus a cross-sectional comparison between individuals with NAFLD and healthy control. Individuals with NAFLD were allocated into two groups receiving resistance training (RT) combined with high-intensity interval training (HIIT) or moderate-intensity continuous training (MICT). Anthropometric indicators, clinical blood markers about glucose, lipid metabolism, and hepatic fat content (HFC) were assessed before and after the intervention. The metabolomics was also used to investigate the discrepant metabolites and mechanisms related to MetF.

Discussion

Metabolic flexibility reflects the capacity of an organism to switch the oxidation substrates flexibly, which is associated with ectopic fat accumulation. Our study aimed to explore the discrepant metabolites related to MetF before and after a high-fat diet between individuals with NAFLD and healthy control. In addition, the study also examined the effectiveness of RT combined with HIIT or MICT on hepatic fat reduction and quantificationally analyzed the metabolites related to MetF before and after the intervention. Our results provided a perspective on fatty liver-associated metabolic inactivity.

Trial registration

ClinicalTrials.gov: ChiCTR2200055110; Registered 31 December 2021, http://www.chictr.org.cn/index.aspx.

High-Intensity Interval Training is Safe, Feasible and Efficacious in Nonalcoholic Steatohepatitis: A Randomized Controlled Trial

BACKGROUND

High-Intensity Interval Training (HIIT) involves bursts of high-intensity exercise interspersed with lower-intensity exercise recovery. HIIT may benefit cardiometabolic health in people with nonalcoholic steatohepatitis (NASH).

AIMS

We aimed to examine the safety, feasibility, and efficacy of 12-weeks of supervised HIIT compared with a sham-exercise control (CON) for improving aerobic fitness and peripheral insulin sensitivity in biopsy-proven NASH.

METHODS

Participants based in the community [(n = 14, 56 ± 10 years, BMI 39.2 ± 6.7 kg/m², 64% male), NAFLD Activity Score 5 (range 3-7)] were randomized to 12-weeks of supervised HIIT (n = 8, 4 × 4 min at 85-95% maximal heart rate, interspersed with 3 min active recovery; 3 days/week) or CON (n = 6, stretching; 3 days/week). Safety (adverse events) and feasibility determined as ≥ 70% program completion and ≥ 70% global adherence (including session attendance, interval intensity adherence, and duration adherence) were assessed. Changes in cardiorespiratory fitness (V̇O₂peak), exercise capacity (time-on-test) and peripheral insulin sensitivity (euglycemic hyperinsulinemic clamp) were assessed. Data were analysed using ANCOVA with baseline value as the covariate.

RESULTS

There were no HIIT-related adverse events and HIIT was globally feasible [program completion 75%, global adherence 100% (including adherence to session 95.4 ± 7.3%, interval intensity 95.3 ± 6.0% and duration 96.8 ± 2.4%)]. A large between-group effect was observed for exercise capacity [mean difference 134.2 s (95% CI 19.8, 248.6 s), ƞ² 0.44, p = 0.03], improving in HIIT (106.2 ± 97.5 s) but not CON (- 33.4 ± 43.3 s), and for peripheral insulin sensitivity [mean difference 3.4 mg/KgLegFFM/min (95% CI 0.9,6.8 mg/KgLegFFM/min), ƞ² 0.32, p = 0.046], improving in HIIT (1.0 ± 0.8 mg/KgLegFFM/min) but not CON (- 3.1 ± 1.2 mg/KgLegFFM/min).

CONCLUSIONS

HIIT is safe, feasible and efficacious for improving exercise capacity and peripheral insulin sensitivity in people with NASH.

CLINICAL TRIAL REGISTRATION NUMBER

Australian New Zealand Clinical Trial Registry (anzctr.org.au) identifier ACTRN12616000305426 (09/03/2016).

Comparison of the effects of high-intensity interval training and moderate-intensity continuous training on indices of liver and muscle tissue in high-fat diet-induced male rats with non-alcoholic fatty liver disease

Background

Non-alcoholic fatty liver disease (NAFLD) is one of the most prevalent chronic liver diseases. It is shown that moderate to high physical activities can play a crucial role in improving this disease.

Aim

The purpose of this study was to explore the effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on the levels of the myonectin in serum and tissue levels and fatty acid transport protein 4 (FATP4) in male rats with NAFLD.

Materials and methods

Thirty-three male rats were randomly divided into five groups: high-fat diet to confirm NAFLD induction (n = 5), normal diet sedentary (n = 7), high-fat diet sedentary (n = 7), high-fat diet with HIIT (n = 7), and high-fat diet with MCIT (n = 7). Induction of NAFLD was performed by feeding rats for 12 weeks with a high-fat diet containing 60% fat. The training protocols were performed in five sessions per week for 8 weeks. The HIIT group has performed 4 × 4 min interval running on a treadmill up to 80–95% maximal oxygen uptake (VO2max) and then recovered at 50–60% VO2max. The MICT protocol has performed up to 50–60% VO2max for 50 min. myonectin and FATP4 were also measured by the animal Elisa kit (Zellbio, Germany) with a sensitivity of 0.02 ng/L. Insulin resistance was evaluated by the insulin resistance homeostasis assessment index using the following formula (HOMA-IR): “fasting glucose (mg/dl) × fasting in insulin (mg/L) ÷ 405”. One-way ANOVA analysis of variance was utilized for statistical analyses and Tukey’s post hoc test at a significant level of p < 0.05.

Results

The 8-week intervention showed that both HIIT and MICT positively influenced the serum myonectin and FATP4 levels (p < 0.05). Moreover, there was a significant difference between the trained groups in tissue levels of the myonectin and serum levels of FATP4 (p < 0.05).

Conclusions

Altogether, both HIIT and MICT can lead to valuable adaptations and recovery of NAFLD in male rats.

Does aerobic exercise reduce NASH and liver fibrosis in patients with non-alcoholic fatty liver disease? A systematic literature review and meta-analysis

Background

Exercise is an effective strategy for the prevention and regression of hepatic steatosis in patients with non-alcoholic fatty liver disease (NAFLD), but it is unclear whether it can reduce advanced stages of NAFLD, i.e., steatohepatitis and liver fibrosis. Furthermore, it is not evident which modality of exercise is optimal to improve/attenuate NAFLD.

Objectives

The aim is to systematically review evidence for the effect of aerobic exercise (AE) on NAFLD, in particular non-alcoholic steatohepatitis (NASH) and liver fibrosis.

Methods

A systematic literature search was conducted in Medline and Embase. Studies were screened and included according to predefined criteria, data were extracted, and the quality was assessed by Cochrane risk of bias tools by two researchers independently according to the protocol registered in the PROSPERO database (CRD42021270059). Meta-analyses were performed using a bivariate random-effects model when there were at least three randomized intervention studies (RCTs) with similar intervention modalities and outcome.

Results

The systematic review process resulted in an inclusion a total of 24 studies, 18 RCTs and six non-RCTs, encompassing 1014 patients with NAFLD diagnosed by histological or radiological findings. Studies were grouped based on the type of AE: moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT). A total of twelve meta-analyses were conducted. Compared to controls, MICT resulted in a mean difference (MD) in the NAFLD biomarkers alanine transaminase (ALT) and aspartate aminotransferase (AST) of -3.59 (CI: -5.60, -1.59, p<0.001) and -4.05 (CI: -6.39, -1.71, p<0.001), respectively. HIIT resulted in a MD of -4.31 (95% CI: -9.03, 0.41, p=0.07) and 1.02 (95% CI: -6.91, 8.94, p=0.8) for ALT and AST, respectively. Moreover, both AE types compared to controls showed a significantly lower magnetic resonance spectroscopy (MRS) determined liver fat with a MD of -5.19 (95% CI: -7.33, -3.04, p<0.001) and -3.41 (95% CI: -4.74, -2.08, p<0.001), for MICT and HIIT respectively. MICT compared to controls resulted in a significantly higher cardiorespiratory fitness (MD: 4.43, 95% CI: 0.31, 8.55, p=0.03).

Conclusion

Liver fat is decreased by AE with a concomitant decrease of liver enzymes. AE improved cardiorespiratory fitness. Further studies are needed to elucidate the impact of different types of AE on hepatic inflammation and fibrosis.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier (CRD42021270059).

The role of exercise intensity on fatty liver in rats

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and is often caused by obesity. Currently, moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) are two effective treatments for reducing fat mass in patients with obesity and NAFLD. However, the comparative fat-reducing effects and underlying molecular mechanisms of MICT and HIIT remain unclear. This comprehensive study was performed on male Wistar rats treated with standard diet, high-fat diet, MICT, and HIIT to explore their comparative fat-reducing effects and corresponding molecular mechanisms. HIIT had a greater effect on hepatic vacuolation density and lipid content reduction than MICT, and triglyceride and total cholesterol levels in the serum and the liver demonstrated different sensitivities to different exercise training programs. At the molecular level, both MICT and HIIT altered the processes of fatty acid synthesis, fatty acid transport, fatty acid β-oxidation, and cholesterol synthesis, wherein the transcriptional and translational levels of signaling molecules peroxisome proliferator-activated receptors (PPARs) regulating fatty acid and cholesterol synthesis were strongly changed. Moreover, the metabolic pathways of amino acids, bile acids, and carbohydrates were also affected according to transcriptome analysis, and the changes in the above-mentioned processes in the HIIT group were greater than those in the MICT group. In combination with the search tool for the retrieval of interacting genes/proteins (STRING) analysis and the role of PPARs in lipid metabolism, as well as the expression pattern of PPARs in the MICT and HIIT groups, the MICT-and HIIT-induced fat loss was mediated by the PPAR pathway, causing feedback responses in fatty acid, steroid, amino acid, bile acid, and carbohydrate metabolism, and HIIT had a better fat-reducing effect, which may be initiated by PPAR-α. This study provides a theoretical basis for targeted therapy of patients with obesity and NAFLD.