Shelley E. Keating

Exercise and non-alcoholic fatty liver disease: a systematic review and meta-analysis.

BACKGROUND & AIMS Exercise is an integral component of lifestyle intervention aimed at weight loss, but an independent benefit of exercise in NAFLD has also been suggested. METHODS We aimed to evaluate the efficacy of aerobic exercise and/or progressive resistance training for the modulation of liver fat and alanine aminotransferase (ALT) levels in adults. Relevant databases were searched up to August 2011 for controlled trials, which compared regular exercise vs. a non-exercise control on change in liver fat and/or ALT. RESULTS Of the 16,822 studies from the initial search, 12 were included. There was a significant pooled effect size (ES) for the comparison between exercise therapy vs. control (ES=-0.37, 95% CI: -0.06 to -0.69; p=0.02), but only when interventions which compared combined exercise and diet vs. diet-alone and achieved substantial weight loss, were omitted. The benefit of exercise on liver fat occurred with minimal or no weight loss. There was no effect of exercise alone vs. control on ALT (ES=-0.15, 95% CI: 0.14 to -0.45; p=0.32). CONCLUSIONS Individual reports of exercise interventions often have low sample sizes and insufficient power to detect clinically meaningful hepatic benefits. By pooling current research, we show clear evidence for a benefit of exercise therapy on liver fat but not ALT levels. This benefit is apparent with minimal or no weight loss and at exercise levels below current exercise recommendations for obesity management. Given the paucity of current treatment options, exercise provides a valid, low-cost therapy for disorders characterised by fatty liver.

A systematic review and meta-analysis of the effect of aerobic vs. resistance exercise training on visceral fat

It is increasingly recognized that the location of excess adiposity, particularly increased deposition of visceral adipose tissue (VAT), is important when determining the adverse health effects of overweight and obesity. Exercise therapy is an integral component of obesity management, but the most potent exercise prescription for VAT benefit is unclear. We aimed to evaluate the independent and synergistic effects of aerobic exercise (AEx) and progressive resistance training (PRT) and to directly compare the efficacy of AEx and PRT for beneficial VAT modulation. A systematic review and meta‐analysis was performed to assess the efficacy of exercise interventions on VAT content/volume in overweight and obese adults. Relevant databases were searched to November 2010. Included studies were randomized controlled designs in which AEx or PRT in isolation or combination were employed for 4 weeks or more in adult humans, where computed tomography (CT) or magnetic resonance imaging (MRI) was used for quantification of VAT pre‐ and post‐intervention. Of the 12196 studies from the initial search, 35 were included. After removal of outliers, there was a significant pooled effect size (ES) for the comparison between AEx therapy and control (−0.33, 95% CI: −0.52 to −0.14; P < 0.01) but not for the comparison between PRT therapy and control (0.09, 95% CI: −0.17 to −0.36; P = 0.49). Of the available nine studies which directly compared AEx with PRT, the pooled ES did not reach statistical significance (ES = 0.23, 95% CI: −0.02 to 0.50; P = 0.07 favouring AEx). The pooled ES did not reach statistical significance for interventions that combined AEx and PRT therapy vs. control (−0.28, 95% CI: −0.69 to 0.14; P = 0.19), for which only seven studies were available. These data suggest that aerobic exercise is central for exercise programmes aimed at reducing VAT, and that aerobic exercise below current recommendations for overweight/obesity management may be sufficient for beneficial VAT modification. Further investigation is needed regarding the efficacy and feasibility of multi‐modal training as a means of reducing VAT.

Effect of aerobic exercise training dose on liver fat and visceral adiposity

BACKGROUND & AIMS Aerobic exercise reduces liver fat and visceral adipose tissue (VAT). However, there is limited data from randomized trials to inform exercise programming recommendations. This study examined the efficacy of commonly prescribed exercise doses for reducing liver fat and VAT using a randomized placebo-controlled design. METHODS Inactive and overweight/obese adults received 8 weeks of either; i) low to moderate intensity, high volume aerobic exercise (LO:HI, 50% VO 2peak, 60 min, 4d/week); ii) high intensity, low volume aerobic exercise (HI:LO, 70% VO 2peak, 45 min, 3d/week); iii) low to moderate intensity, low volume aerobic exercise (LO:LO, 50% VO 2peak, 45 min, 3d/week); or iv) placebo (PLA). Liver fat (spectroscopy) and VAT (magnetic resonance imaging) were measured before and after intervention. RESULTS Forty-seven of the 48 (n = 12 in each group) participants completed the trial. There were no serious adverse events. There was a significant change in group × time interaction in liver fat, which reduced in HI:LO by 2.38 ± 0.73%, in LO:HI by 2.62 ± 1.00%, and in LO:LO by 0.84 ± 0.47% but not in PLA (increase of 1.10 ± 0.62%) (p = 0.04). There was a significant reduction in VAT in HI:LO (-258.38 ± 87.78 cm(3)), in LO:HI (-386.80 ± 119.5 cm(3)), and in LO:LO (-212.96 ± 105.54 cm(3)), but not in PLA (92.64 ± 83.46 cm(3)) (p = 0.03). There were no significant differences between the dose or intensity of the exercise regimen and reductions in liver fat or VAT (p > 0.05). CONCLUSION The study found no difference in efficacy of liver fat reduction by either aerobic exercise dose or intensity. All of the aerobic exercise regimens employed reduced liver fat and VAT by a small amount without clinically significant weight loss.

Accuracy of Heart Rate Watches: Implications for Weight Management

Background Wrist-worn monitors claim to provide accurate measures of heart rate and energy expenditure. People wishing to lose weight use these devices to monitor energy balance, however the accuracy of these devices to measure such parameters has not been established. Aim To determine the accuracy of four wrist-worn devices (Apple Watch, Fitbit Charge HR, Samsung Gear S and Mio Alpha) to measure heart rate and energy expenditure at rest and during exercise. Methods Twenty-two healthy volunteers (50% female; aged 24 ± 5.6 years) completed ~1-hr protocols involving supine and seated rest, walking and running on a treadmill and cycling on an ergometer. Data from the devices collected during the protocol were compared with reference methods: electrocardiography (heart rate) and indirect calorimetry (energy expenditure). Results None of the devices performed significantly better overall, however heart rate was consistently more accurate than energy expenditure across all four devices. Correlations between the devices and reference methods were moderate to strong for heart rate (0.67–0.95 [0.35 to 0.98]) and weak to strong for energy expenditure (0.16–0.86 [-0.25 to 0.95]). All devices underestimated both outcomes compared to reference methods. The percentage error for heart rate was small across the devices (range: 1–9%) but greater for energy expenditure (9–43%). Similarly, limits of agreement were considerably narrower for heart rate (ranging from -27.3 to 13.1 bpm) than energy expenditure (ranging from -266.7 to 65.7 kcals) across devices. Conclusion These devices accurately measure heart rate. However, estimates of energy expenditure are poor and would have implications for people using these devices for weight loss.

Continuous Exercise but Not High Intensity Interval Training Improves Fat Distribution in Overweight Adults

Objective. The purpose of this study was to assess the effect of high intensity interval training (HIIT) versus continuous aerobic exercise training (CONT) or placebo (PLA) on body composition by randomized controlled design. Methods. Work capacity and body composition (dual-energy X-ray absorptiometry) were measured before and after 12 weeks of intervention in 38 previously inactive overweight adults. Results. There was a significant group × time interaction for change in work capacity (P < 0.001), which increased significantly in CONT (23.8 ± 3.0%) and HIIT (22.3 ± 3.5%) but not PLA (3.1 ± 5.0%). There was a near-significant main effect for percentage trunk fat, with trunk fat reducing in CONT by 3.1 ± 1.6% and in PLA by 1.1 ± 0.4%, but not in HIIT (increase of 0.7 ± 1.0%) (P = 0.07). There was a significant reduction in android fat percentage in CONT (2.7 ± 1.3%) and PLA (1.4 ± 0.8%) but not HIIT (increase of 0.8 ± 0.7%) (P = 0.04). Conclusion. These data suggest that HIIT may be advocated as a time-efficient strategy for eliciting comparable fitness benefits to traditional continuous exercise in inactive, overweight adults. However, in this population HIIT does not confer the same benefit to body fat levels as continuous exercise training.

Exercise and the liver: Implications for therapy in fatty liver disorders

The increasing recognition that fatty liver plays a direct role in the pathogenesis of cardiovascular and metabolic disease has resulted in significant research enquiry into the efficacy of lifestyle therapy in modulating liver fat. Recently, this has extended to the specific investigation of a possible independent benefit of physical activity/exercise in nonalcoholic fatty liver disease (NAFLD). In this article we review the effect of acute and regular exercise (training) on metabolism, including liver glucose and lipid metabolism, and the available human trials that have compared the benefit of regular exercise versus a nonexercise control on liver fat. The limited human research suggests that exercise can reduce liver fat and that this benefit may be mediated, in part, by a reduction in hepatic lipogenesis. The relative importance of extrahepatic adaptations and acute versus regular exercise in explaining this benefit are discussed. From a clinical perspective, the revelation of a benefit of exercise per se offers a novel approach for liver fat reduction, and highlights the importance of incorporating fitness assessment and prescription in the management of patients with fatty liver disorders. Implementation of exercise therapy in a clinical setting is arguably the biggest challenge because evidence shows that mere provision of information about the benefits of exercise and/or exercise prescription to the patient does not translate to positive outcomes. Rather, the focus should be on implementing strategies to promote behavior change including regular contact and assessment with a health care professional, self-monitoring, and personalization of goals that focus on changing physical activity behavior.

A systematic review and meta‐analysis of interval training versus moderate‐intensity continuous training on body adiposity

Interval training (including high‐intensity interval training [HIIT] and sprint interval training [SIT]) is promoted in both scientific and lay media as being a superior and time‐efficient method for fat loss compared with traditional moderate‐intensity continuous training (MICT). We evaluated the efficacy of HIIT/SIT when directly compared with MICT for the modulation of body adiposity. Databases were searched to 31 August 2016 for studies with exercise training interventions with minimum 4‐week duration. Meta‐analyses were conducted for within‐group and between‐group comparisons for total body fat percentage (%) and fat mass (kg). To investigate heterogeneity, we conducted sensitivity and meta‐regression analyses. Of the 6,074 studies netted, 31 were included. Within‐group analyses demonstrated reductions in total body fat (%) (HIIT/SIT: −1.26 [95% CI: −1.80; −0.72] and MICT: −1.48 [95% CI: −1.89; −1.06]) and fat mass (kg) (HIIT/SIT: −1.38 [95% CI: −1.99; −0.77] and MICT: −0.91 [95% CI: −1.45; −0.37]). There were no differences between HIIT/SIT and MICT for any body fat outcome. Analyses comparing MICT with HIIT/SIT protocols of lower time commitment and/or energy expenditure tended to favour MICT for total body fat reduction (p = 0.09). HIIT/SIT appears to provide similar benefits to MICT for body fat reduction, although not necessarily in a more time‐efficient manner. However, neither short‐term HIIT/SIT nor MICT produced clinically meaningful reductions in body fat.

The benefits of exercise for patients with non-alcoholic fatty liver disease

As exercise is now an established therapy for the management of non-alcoholic fatty liver disease (NAFLD), recent investigations have sought to identify the optimal dose (type, intensity and amount) of exercise for hepatic benefit. Here, the authors discuss the following: the role of aerobic exercise for the modulation of hepatic steatosis; the limited evidence for the role of resistance training in reducing liver fat; the lack of evidence from clinical trials on the role of exercise in non-alcoholic steatohepatitis; and the benefits of exercise for patients with NAFLD, beyond steatosis. Based on current evidence, the authors provide recommendations for exercise prescription for patients with NAFLD.

The Effect of Exercise on Vascular Function and Stiffness in Type 2 Diabetes: A Systematic Review and Meta-analysis

Deterioration of the structure and function of the vascular system is the underlying feature in cardiovascular disease (CVD), which is the highest cause of mortality in type 2 diabetes (T2D). Studies assessing the effect of exercise on vascular function and stiffness have used different measurement techniques and small cohorts, making it difficult to conclude on the overall efficacy of exercise on these outcomes. The aim of this study was to assess the effect of exercise on vascular function and stiffness in T2D. Electronic database searches were performed in AMED, MEDLINE, MEDLINE Daily Update, PREMEDLINE, SPORTDiscus, CINAHL, EMBASE and Web of Science. The effect size (ES), and 95% confidence intervals (CIs) of eligible studies were calculated. Pooled estimates of the effect of aerobic exercise (AEx) on vascular function and stiffness, using ES, were obtained. Results show that AEx led to a near-significant reduction in PWV (ES = -0.472; 95% CI: -0.949 to 0.005; P = 0.052), a significant reduction in EID (ES = 0.416, 95% CI: 0.062 to 0.769; P= 0.021), and a non-significant benefit in FMD measures. There were limited studies using resistance training or in combination with aerobic exercise, to assess a pooled effect on vascular function or stiffness. These data suggest that aerobic exercise training should be used as a primary treatment strategy for improving vascular smooth muscle function as measured by EID in individuals with T2D. There is currently insufficient evidence concerning the efficacy of regular exercise for improving vascular function and stiffness as measured by FMD and PWV.

Effects of exercise intensity and nutrition advice on myocardial function in obese children and adolescents: a multicentre randomised controlled trial study protocol

Introduction The prevalence of paediatric obesity is increasing, and with it, lifestyle-related diseases in children and adolescents. High-intensity interval training (HIIT) has recently been explored as an alternate to traditional moderate-intensity continuous training (MICT) in adults with chronic disease and has been shown to induce a rapid reversal of subclinical disease markers in obese children and adolescents. The primary aim of this study is to compare the effects of HIIT with MICT on myocardial function in obese children and adolescents. Methods and analysis Multicentre randomised controlled trial of 100 obese children and adolescents in the cities of Trondheim (Norway) and Brisbane (Australia). The trial will examine the efficacy of HIIT to improve cardiometabolic outcomes in obese children and adolescents. Participants will be randomised to (1) HIIT and nutrition advice, (2) MICT and nutrition advice or (3) nutrition advice. Participants will partake in supervised exercise training and/or nutrition sessions for 3 months. Measurements for study end points will occur at baseline, 3 months (postintervention) and 12 months (follow-up). The primary end point is myocardial function (peak systolic tissue velocity). Secondary end points include vascular function (flow-mediated dilation assessment), quantity of visceral and subcutaneous adipose tissue, myocardial structure and function, body composition, cardiorespiratory fitness, autonomic function, blood biochemistry, physical activity and nutrition. Lean, healthy children and adolescents will complete measurements for all study end points at one time point for comparative cross-sectional analyses. Ethics and dissemination This randomised controlled trial will generate substantial information regarding the effects of exercise intensity on paediatric obesity, specifically the cardiometabolic health of this at-risk population. It is expected that communication of results will allow for the development of more effective evidence-based exercise prescription guidelines in this population while investigating the benefits of HIIT on subclinical markers of disease. Trial registration number NCT01991106.