The association between cardiorespiratory fitness, liver fat and insulin resistance in adults with or without type 2 diabetes : a cross-sectional analysis

Background: Exercise-induced improvements in cardiorespiratory fitness (CRF) often coincide with improvements in insulin sensitivity and reductions in liver fat content. However, there are limited data concerning the relationship between CRF and liver fat content in adults with varying degrees of metabolic dysfunction. Methods: The aim of this study was to examine the association between CRF, liver fat content, and insulin resistance in inactive adults with obesity and with or without type 2 diabetes (T2D), via cross-sectional analysis. CRF was determined via a graded exercise test. Liver fat content was assessed via proton magnetic resonance spectroscopy and insulin resistance was assessed via homeostatic model of insulin resistance (HOMA-IR). A partial correlation analysis, controlling for age and gender, was performed to determine the association between CRF, demographic, cardiometabolic, and anthropometric variables. Independent t tests were performed to compare cardiometabolic outcomes between participants with T2D and participants without T2D. Results: Seventy-two adults (46% male) with a mean age of 49.28 ± 10.8 years, BMI of 34.69 ± 4.87 kg/m2 , liver fat content of 8.37 ± 6.90%, HOMA-IR of 3.07 ± 2.33 and CRF of 21.52 ± 3.77 mL/kg/min participated in this study. CRF was inversely associated with liver fat content (r = − 0.28, p = 0.019) and HOMA-IR (r = − 0.40, p < 0.001). Participants with T2D had significantly higher liver fat content (+ 3.66%, p = 0.024) and HOMA-IR (+ 2.44, p < 0.001) than participants without T2D. Participants with T2D tended to have lower CRF than participants without T2D (− 1.5 ml/kg/min, p = 0.094). Conclusion: CRF was inversely associated with liver fat content and insulin resistance. Participants with T2D had lower CRF than those without T2D, however, the difference was not statistically significant. Further longitudinal studies are required to elucidate the relationship between CRF and the progression of obesity-related diseases such as T2D. Registration: ACTRN12614001220651 (retrospectively registered on the 19th November 2014) and ACTRN12614000723684 (prospectively registered on the 8th July 2014)

The efficacy of exercise training for cutaneous microvascular reactivity in the foot in people with diabetes and obesity : secondary analyses from a randomized controlled trial

It is unclear if cutaneous microvascular dysfunction associated with diabetes and obesity can be ameliorated with exercise. We investigated the effect of 12-weeks of exercise training on cutaneous microvascular reactivity in the foot. Thirty-three inactive adults with type 2 diabetes and obesity (55% male, 56.1 +/- 7.9 years, BMI: 35.8 +/- 5, diabetes duration: 7.9 +/- 6.3 years) were randomly allocated to 12-weeks of either (i) moderate-intensity continuous training [50-60% peak oxygen consumption (VO2peak), 30-45 min, 3 d/week], (ii) low-volume high-intensity interval training (90% VO2peak, 1-4 min, 3 d/week) or (iii) sham exercise placebo. Post-occlusive reactive hyperaemia at the hallux was determined by laser-Doppler fluxmetry. Though time to peak flux post-occlusion almost halved following moderate intensity exercise, no outcome measure reached statistical significance (p > 0.05). These secondary findings from a randomised controlled trial are the first data reporting the effect of exercise interventions on cutaneous microvascular reactivity in the foot in people with diabetes. A period of 12 weeks of moderate-intensity or low-volume high-intensity exercise may not be enough to elicit functional improvements in foot microvascular reactivity in adults with type 2 diabetes and obesity. Larger, sufficiently powered, prospective studies are necessary to determine if additional weight loss and/or higher exercise volume is required

The effect of low-volume high-intensity interval training on body composition and cardiorespiratory fitness: a systematic review and meta-analysis

Background: Evidence for the efficacy of low-volume high-intensity interval training (HIIT) for the modulation of body composition is unclear. Objectives: We examined the effect of low-volume HIIT versus a non-exercising control and moderate-intensity continuous training (MICT) on body composition and cardiorespiratory fitness in normal weight, overweight and obese adults. We evaluated the impact of low-volume HIIT (HIIT interventions where the total amount of exercise performed during training was ≤ 500 metabolic equivalent minutes per week [MET-min/week]) compared to a non-exercising control and MICT. Methods: A database search was conducted in PubMed (MEDLINE), EMBASE, CINAHL, Web of Science, SPORTDiscus and Scopus from the earliest record to June 2019 for studies (randomised controlled trials and non-randomised controlled trials) with exercise training interventions with a minimum 4-week duration. Meta-analyses were conducted for between-group (low-volume HIIT vs. non-exercising control and low-volume HIIT vs. MICT) comparisons for change in total body fat mass (kg), body fat percentage (%), lean body mass (kg) and cardiorespiratory fitness. Results: From 11,485 relevant records, 47 studies were included. No difference was found between low-volume HIIT and a non-exercising control on total body fat mass (kg) (effect size [ES]: − 0.129, 95% confidence interval [CI] − 0.468 to 0.210; p = 0.455), body fat (%) (ES: − 0.063, 95% CI − 0.383 to 0.257; p = 0.700) and lean body mass (kg) (ES: 0.050, 95% CI − 0.250 to 0.351; p = 0.744), or between low-volume HIIT and MICT on total body fat mass (kg) (ES: − 0.021, 95% CI − 0.272 to 0.231; p = 0.872), body fat (%) (ES: 0.005, 95% CI − 0.294 to 0.304; p = 0.974) and lean body mass (kg) (ES: 0.030, 95% CI − 0.167 to 0.266; p = 0.768). However, low-volume HIIT significantly improved cardiorespiratory fitness compared with a non-exercising control (p < 0.001) and MICT (p = 0.017). Conclusion: These data suggest that low-volume HIIT is inefficient for the modulation of total body fat mass or total body fat percentage in comparison with a non-exercise control and MICT. A novel finding of our meta-analysis was that there appears to be no significant effect of low-volume HIIT on lean body mass when compared with a non-exercising control, and while most studies tended to favour improvement in lean body mass with low-volume HIIT versus MICT, this was not significant. However, despite its lower training volume, low-volume HIIT induces greater improvements in cardiorespiratory fitness than a non-exercising control and MICT in normal weight, overweight and obese adults. Low-volume HIIT, therefore, appears to be a time-efficient treatment for increasing fitness, but not for the improvement of body composition

The association between cardiorespiratory fitness and NAFLD in overweight and obese adults

Introduction: Cardiorespiratory fitness (CRF) is a known independent risk factor for morbidity and mortality (1). Furthermore, CRF and obesity have been shown to be associated with impaired fasting glucose (IFG) and type 2 diabetes (T2D) by similar magnitudes (2). Nonalcoholic fatty liver disease (NAFLD) is also associated with IFG and T2D, and increases in CRF has been shown to mitigate IFG and insulin resistance. The primary aim of this study was to explore the association between CRF and NAFLD in inactive adults with overweight and obesity. A secondary aim was to examine the possible association between CRF and NAFLD independent of known demographic and anthropometric risk factors. Methods: CRF, IHL, and other demographic, anthropometric and biochemical risk factors were assessed in 67 inactive, overweight and obese adults with and without diabetes. CRF was measured via a graded exercise test (Lode Corival cycle ergometer). NAFLD was assessed by grading participants’ liver fat concentration via proton magnetic spectroscopy (where a liver fat score >5.5% was classified as NAFLD positive). Bivariate regression and hierarchical multiple regression analyses were performed. RESULTS: CRF was not associated with NAFLD (p=0.49) nor liver fat concentration (p=0.09). CRF was associated with other cardiometabolic risk factors such as fasting blood glucose (p=0.02), fasting serum insulin (p=0.02) and systolic blood pressure (p=0.04), however these associations were not independent of BMI. Conclusion: Our findings showed that CRF was not associated with NAFLD in inactive, overweight and obese adults, with and without diabetes. Additional studies incorporating a greater variation in CRF are needed to further explore the relationship between CRF and liver fat

The effect of high intensity interval training versus moderate intensity continuous training on arterial stiffness and 24 h blood pressure responses : a systematic review and meta-analysis

Objectives: Greater arterial stiffness and poor 24 h blood pressure (BP) are recognized as indicators of poor cardiovascular health. Evidence has shown that high intensity interval training (HIIT) may be a superior alternative to moderate intensity continuous training (MICT) for improving cardiovascular disease risk factors such as cardiorespiratory fitness and vascular function. However, there are limited data comparing the effect of HIIT to MICT on central arterial stiffness and/or 24 h BP response. The purpose of this study was to compare HIIT versus MICT on central arterial stiffness and 24 h BP outcomes by systematic review and meta-analysis. Design: A systematic review and meta-analysis was conducted. Methods: Eligible studies were exercise training interventions (≥4 weeks) that included both HIIT and MICT and reported central arterial stiffness, as measured by pulse wave velocity and augmentation index and/or 24 h BP outcome measures. Results: HIIT was found to be superior to MICT for reducing night-time diastolic BP (ES: −0.456, 95% CI: −0.826 to −0.086 mmHg; P = 0.016). A near-significant greater reduction in daytime systolic (ES: −0.349, 95% CI: −0.740 to 0.041 mmHg; p = 0.079) and diastolic BP was observed with HIIT compared to MICT (ES: −0.349, 95% CI: −0.717 to 0.020 mmHg; p = 0.063). No significant difference was found for other BP responses or arterial stiffness outcomes. Conclusions: HIIT leads to a superior reduction in night-time diastolic BP compared to MICT. Furthermore, a near-significant greater reduction in daytime BP was found with HIIT compared to MICT. No significant difference was observed for changes to central arterial stiffness between HIIT and MICT

The effect of exercise on visceral fat in type 2 diabetes

Introduction: It is widely acknowledged that obesity increases cardiovascular and metabolic morbidity and mortality, and that visceral adipose tissue (VAT) is a major contributor to adverse cardiometabolic health in obesity-related type 2 diabetes. Although it is increasingly recognised that regular exercise has little effect on long-term weight loss, numerous investigations have reported a multiplicity of other benefits, including a reduction in VAT. A systematic review and meta-analysis was performed to assess the efficacy of exercise interventions on VAT area/volume in overweight and obese adults with type 2 diabetes. Methods: Relevant databases were searched to February 2016. Inclusion criteria included randomised controlled studies in which aerobic exercise training (AEx) or progressive resistance training (PRT) was used exclusively, or in combination for a minimum period of 4 weeks. Studies were selected if computed tomography or magnetic resonance imagining were used for the quantification of VAT area/volume pre- and post-intervention. Results: The original search included 7,588 studies, of which 15 were selected based on the eligibility criteria. After the removal of outliers, a significant pooled effect size (ES) was found for the comparison between AEx and control (-0.23, 95%CI:-0.43 to –0.03; P=0.026), but not for the comparison between PRT and control (-0.13, 95%CI:-0.37 to 0.12; P=0.307) or combination therapy and control (-0.11, 95%CI:-0.36 to 0.13 P=0.374). Conclusion: When compared with a control intervention, AEx therapy is effective for lowering VAT. Conversely, when compared with control, PRT in isolation or in combination with AEx may not reduce VAT. These data suggest that AEx is more efficacious for reducing VAT in overweight/obese populations with type 2 diabetes. Due to the small sample size of multi-modal and resistance training interventions, further investigation is needed to determine the efficacy of these therapies for VAT benefit

The effect of low-volume high-intensity interval training on cardiovascular health outcomes in type 2 diabetes: a&nbsp;randomised controlled trial

Background: Low-volume high-intensity interval training (HIIT) may be a time-efficient strategy that leads to similar or superior improvements in cardiorespiratory fitness (CRF) and cardiovascular disease (CVD) risk factors when compared with moderate-intensity continuous training (MICT). Our study investigated the effect of low-volume HIIT or MICT versus sham placebo-control (PLA) on central arterial stiffness, hemodynamic responses, and CVD risk factors in adults with obesity and type 2 diabetes (T2D).Methods: Eligible participants were previously inactive adults with obesity and T2D. Individuals were randomly allocated to: i) HIIT (1\ua0×\ua04 min cycling at 90% peak oxygen consumption [V̇O2peak]); ii) MICT (45\ua0min of cycling at 60% VO2peak); or PLA. Training groups exercised thrice weekly for 12\ua0weeks. Central arterial stiffness, hemodynamics and CVD risk factors were assessed at baseline and post-intervention. Analysis of covariance (ANCOVA) was used to examine changes following HIIT, MICT and PLA.Results: Thirty-five participants (age: 55.1\ua0±\ua01.4\ua0years, BMI: 36.1\ua0±\ua00.8\ua0kg/m2) completed the study. A significant intervention effect was found for changes in pulse wave velocity (PWV) (p\ua0=\ua0.03), which reduced with HIIT (−0.3\ua0±\ua00.9\ua0m/s) and MICT (−0.1\ua0±\ua01.1\ua0m/s) but increased with PLA (0.8\ua0±\ua01.6\ua0m/s). There was a significant intervention effect for changes in V̇O2peak\ua0(p\ua

Degree of adiposity and obesity severity is associated with cutaneous microvascular dysfunction in type 2 diabetes

Backgrounds and aims: Obesity and diabetes independently contribute to cutaneous microvascular dysfunction via pathological processes that are not fully understood. We sought to determine if obesity severity is associated with cutaneous microvascular dysfunction and measures of peripheral arterial disease in adults with type 2 diabetes in cross-sectional observational study design. Methods and results: Primary outcomes were post-occlusive reactive hyperaemia as determined by laser-Doppler fluxmetry (peak flux post-occlusion, time to peak flux post-occlusion, peak as a percentage of baseline, and area under the curve [AuC] index post-occlusion to pre-occlusion). Secondary outcomes were ankle- and toe-brachial indices (ABI and TBI) and systolic toe pressure. Thirty-six participants (20 men, 16 women) with mean age 55 ± 8 years, BMI of 36 ± 5 kg/m2 and duration of diabetes 8 ± 6 years underwent measurements. After adjusting for age and duration of diabetes, SAT and total percentage body fat were able to explain 29% (p = 0.001) and 20% (p = 0.01) of variance of AuC index models, as well as 29% (p = 0.02) and 18% (p = 0.02) of peak as a percentage of baseline models, respectively. Though TBI demonstrated moderate, significant correlations with SAT (r:0.37, p = 0.04) and total percentage body fat (r:0.39, p = 0.03), these were not upheld by regression analyses. Neither ABI nor systolic toe pressure significantly correlated with any measure of adiposity or obesity. Conclusion: These findings demonstrate impairment in cutaneous microvascular function related to adiposity and obesity severity in adults with type 2 diabetes, suggesting that obesity may pathologically effect cutaneous microvascular function in the absence of overt macrovascular disease, warranting further investigation

The effect of a novel low-volume aerobic exercise intervention on liver fat in type 2 diabetes: a randomized controlled trial

OBJECTIVE: The aim of this study was to examine the effect of a novel low-volume high-intensity interval training (HIIT), moderate-intensity continuous training (MICT), or placebo (PLA) intervention on liver fat, glycemia, and cardiorespiratory fitness using a randomized placebo-controlled design. RESEARCH DESIGN AND METHODS: Thirty-five inactive adults (age 54.6 ± 1.4 years, 54% male; BMI 35.9 ± 0.9 kg/m2) with obesity and type 2 diabetes were randomized to 12 weeks of supervised MICT (n = 12) at 60% VO2peak for 45 min, 3 days/week; HIIT (n = 12) at 90% VO2peak for 4 min, 3 days/week; or PLA (n = 11). Liver fat percentage was quantified through proton MRS. RESULTS: Liver fat reduced in MICT (-0.9 ± 0.7%) and HIIT (-1.7 ± 1.1%) but increased in PLA (1.2 ± 0.5%) (P = 0.046). HbA1c improved in MICT (-0.3 ± 0.3%) and HIIT (-0.3 ± 0.3%) but not in PLA (0.5 ± 0.2%) (P = 0.014). Cardiorespiratory fitness improved in MICT (2.3 ± 1.2 mL/kg/min) and HIIT (1.1 ± 0.5 mL/kg/min) but not in PLA (-1.5 ± 0.9 mL/kg/min) (P = 0.006). CONCLUSIONS: MICT or a low-volume HIIT approach involving 12 min of weekly high-intensity aerobic exercise may improve liver fat, glycemia, and cardiorespiratory fitness in people with type 2 diabetes in the absence of weight loss. Further studies are required to elucidate the relationship between exercise-induced reductions in liver fat and improvements in glycemia