Effects of aerobic training with and without weight loss on insulin sensitivity and lipids

Purpose: The purpose of this study is to evaluate the effect of exercise training with modest or greater weight loss (≥3%) or not (<3%) on insulin sensitivity, lipoprotein concentrations, and lipoprotein particle size in overweight and obese participants. Methods: Adults (N = 163, body mass index: 25–37 [kg/m2]) participated in 8 months of exercise training. Insulin sensitivity, lipid concentrations, lipid particle size and other cardiometabolic variables were measured at baseline and follow-up. Participants were categorized by whether they achieved at least modest weight loss (≥ 3%) or not (<3%) following the intervention. Results: A greater improvement in insulin sensitivity was observed in adults performing exercise training with at least modest weight loss (2.2 mU·l-1 ·min -1, CI: 1.5 to 2.8) compared to those who did not (0.8 mU·l-1 ·min -1, CI: 0.5 to 1.2). Similar results were observed for acute insulin response, triglycerides, non-HDL cholesterol concentration, low density lipoprotein (LDL) particle size and high density lipoprotein (HDL) particle size (p<0.05), when all exercise groups were combined. No significant results across weight loss categories were observed for LDL, HDL, glucose, or insulin levels. Conclusion: The present study suggests that aerobic exercise combined with at least modest weight loss leads to greater improvements in insulin sensitivity, triglycerides as well as other non-traditional lipid risk factors (non-HDL cholesterol, HDL/LDL particle size). Clinicians should advocate patients who are overweight/obese to exercise and obtain modest weight loss for improved cardiovascular benefits

Low fitness partially explains resting metabolic rate differences between African American and white women

Background High levels of obesity among African American women have been hypothesized to be partially resultant from a lower resting metabolic rate compared with white women. The aim of the current study was to determine if differences in cardiorespiratory fitness and moderate-to-vigorous physical activity are associated with differences in resting metabolic rate among free-living young adult African American women and white women. Methods Participants were 179 women (white women n = 141, African American women n = 38, mean age = 27.7 years). Resting metabolic rate was measured using indirect calorimetry, body composition using dual energy x-ray absorptiometry, cardiorespiratory fitness via maximal treadmill test, and moderate-to-vigorous physical activity using an activity monitor. Results African American women had higher body mass index, fat mass, and fat-free mass compared with white women but lower levels of cardiorespiratory fitness. No differences were observed between African American and white women in resting metabolic rate when expressed as kcal/day (1390.8 ± 197.5 vs 1375.7 ± 173.6 kcal/day, P =.64), but African American women had a lower resting metabolic rate when expressed relative to body weight (2.56 ± 0.30 vs 2.95 ± 0.33 mL/kg/min,

The Effect of Exercise Training Modality on Serum Brain Derived Neurotrophic Factor Levels in Individuals with Type 2 Diabetes

Introduction: Brain derived neurotrophic factor (BDNF) has been implicated in memory, learning, and neurodegenerative disease. However, the relationship of BDNF with cardiometabolic risk factors is unclear, and the effect of exercise training on BDNF has not been previously explored in individuals with type 2 diabetes. Methods: Men and women (N=150) with type 2 diabetes were randomized to an aerobic exercise (aerobic), resistance exercise (resistance), or a combination of both (combination) for 9 months. Serum BDNF levels were evaluated at baseline and follow-up from archived blood samples. Results: Baseline serum BDNF was not associated with fitness, body composition, anthropometry, glucose control, or strength measures (all, p\u3e0.05). Similarly, no significant change in serum BDNF levels was observed following exercise training in the aerobic (-1649.4 pg/ml, CI: -4768.9 to 1470.2), resistance (-2351.2 pg/ml, CI: -5290.7 to 588.3), or combination groups (-827.4 pg/ml, CI: -3533.3 to 1878.5) compared to the control group (-2320.0 pg/ml, CI: -5750.8 to 1110.8). However, reductions in waist circumference were directly associated with changes in serum BDNF following training (r=0.25, p=0.005). Conclusions: Serum BDF was not associated with fitness, body composition, anthropometry, glucose control, or strength measures at baseline. Likewise, serum BDNF measures were not altered by 9 months of aerobic, resistance, or combination training. However, reductions in waist circumference were associated with decreased serum BDNF levels. Future studies should investigate the relevance of BDNF with measures of cognitive function specifically in individuals with type-2 diabetes

Evaluation of a Workplace Treadmill Desk Intervention: A Randomized Controlled Trial

OBJECTIVE: To evaluate the effectiveness of a 3-month treadmill desk intervention in eliciting changes in physical activity and sedentary behavior among overweight/obese office workers. METHODS: A randomized controlled trial was conducted among overweight/obese office workers (n=41; mean age = 40.1 ± 10.1 years) at a private workplace. Participants were randomly assigned to a shared-treadmill desk intervention (n=21) or a usual working condition control group (n=20). Accelerometer-determined physical activity and sedentary behavior were measured before and after the intervention. RESULTS: Compared with the control group, the intervention group increased daily steps (1622 steps/day; p=0.013) and light physical activity (1.6 minutes/hour; p=0.008), and decreased sedentary time (−3.6 minutes/hour; p=0.047) during working hours. CONCLUSIONS: Shared-treadmill desks in the workplace can be effective at promoting favorable changes in light physical activity (specifically 40-99 steps/minute) and sedentary behavior among overweight/obese office workers.This is a non-final version of an article. The article is copyrighted by the American College of Occupational and Environmental Medicine and published by Lippincott Williams & Wilkins. It can be found as published in final form at: http://journals.lww.com/joem/pages/default.asp

High-intensity exercise to promote accelerated improvements in cardiorespiratory fitness (HI-PACE): study protocol for a randomized controlled trial

Background: African Americans have a disproportionate prevalence and incidence of type 2 diabetes compared with Caucasians. Recent evidence indicates that low cardiorespiratory fitness (CRF) level, an independent risk factor for type 2 diabetes, is also more prevalent in African Americans than Caucasians. Numerous studies in Caucasian populations suggest that vigorous exercise intensity may promote greater improvements in CRF and other type 2 diabetes risk factors (e.g., reduction of glucose/insulin levels, pulse wave velocity, and body fat) than moderate intensity. However, current evidence comparing health benefits of different aerobic exercise intensities on type 2 diabetes risk factors in African Americans is negligible. This is clinically important as African Americans have a greater risk for type 2 diabetes and are less likely to meet public health recommendations for physical activity than Caucasians. The purpose of the HI-PACE (High-Intensity exercise to Promote Accelerated improvements in CardiorEspiratory fitness) study is to evaluate whether high-intensity aerobic exercise elicits greater improvements in CRF, insulin action, and arterial stiffness than moderate-intensity exercise in African Americans. Methods/Design: A randomized controlled trial will be performed on overweight and obese (body mass index of 25–45 kg/m2) African Americans (35–65 years) (n = 60). Participants will be randomly assigned to moderate-intensity (MOD-INT) or high-intensity (HIGH-INT) aerobic exercise training or a non-exercise control group (CON) for 24 weeks. Supervised exercise will be performed at a heart rate associated with 45–55% and 70–80% of VO2 max in the MOD-INT and HIGH-INT groups, respectively, for an exercise dose of 600 metabolic equivalents of task (MET)-minutes per week (consistent with public health recommendations). The primary outcome is change in CRF. Secondary outcomes include change in insulin sensitivity (measured via an intravenous glucose tolerance test), skeletal muscle mitochondrial oxidative capacity (via near-infrared spectroscopy), skeletal muscle measurements (i.e., citrate synthase, COX IV, GLUT-4, CPT-1, and PGC1-α), arterial stiffness (via carotid-femoral pulse wave velocity), body fat, C-reactive protein, and psychological outcomes (quality of life/exercise enjoyment). Discussion: The anticipated results of the HI-PACE study will provide vital information on the health effects of high-intensity exercise in African Americans. This study will advance health disparity research and has the potential to influence future public health guidelines for physical activity

Association between Changes in Muscle Quality with Exercise Training and Changes in Cardiorespiratory Fitness Measures in Individuals with Type 2 Diabetes Mellitus: Results from the HART-D Study

Introduction: Type 2 diabetes mellitus (T2DM) is associated with a reduction in muscle quality. However, there is inadequate empirical evidence to determine whether changes in muscle quality following exercise are associated with improvement in cardiorespiratory fitness (CRF) in individuals with T2DM. The objective of this study was to investigate the association between change in muscle quality following a 9-month intervention of aerobic training (AT), resistance training (RT) or a combination of both (ATRT) and cardiorespiratory fitness (CRF) in individuals with T2DM. Material and Methods A total of 196 participants were randomly assigned to a control, AT, RT, or combined ATRT for a 9-months intervention. The exposure variable was change in muscle quality [(Post: leg muscle strength/leg muscle mass)-[(Pre: leg muscle strength/leg muscle mass)]. Dependent variables were change in CRF measures including absolute and relative VO2peak, and treadmill time to exhaustion (TTE) and estimated metabolic equivalent task (METs). Results Continuous change in muscle quality was independently associated with change in absolute (β = 0.015; p = 0.019) and relative (β = 0.200; p = 0.005) VO2peak, and TTE (β = 0.170; p = 0.043), but not with estimated METs (p > 0.05). A significant trend was observed across tertiles of change in muscle quality for changes in absolute (β = 0.050; p = 0.005) and relative (β = 0.624; p = 0.002) VO2peak following 9 months of exercise training. No such association was observed for change in TTE and estimated METs (p > 0.05). Discussion: The results from this ancillary study suggest that change in muscle quality following exercise training is associated with a greater improvement in CRF in individuals with T2DM. Given the effect RT has on increasing muscle quality, especially as part of a recommended training program (ATRT), individuals with T2DM should incorporate RT into their AT regimens to optimize CRF improvement

WalkMore: a randomized controlled trial of pedometer-based interventions differing on intensity messages

Pedometer-based programs have elicited increased walking behaviors associated with improvements in blood pressure in sedentary/low active postmenopausal women, a population at increased risk of cardiovascular disease. Such programs typically encourage increasing the volume of physical activity with little regard for its intensity. Recent advances in commercially available pedometer technology now permit tracking of both steps/day and time in moderate (or greater) intensity physical activity on a daily basis. It is not known whether the dual message to increase steps/day while also increasing time spent at higher intensity walking will elicit additional improvements in blood pressure relative to a message to only focus on increasing steps/day. The purpose of this paper is to present the rationale, study design, and protocols employed in WalkMore, a 3-arm 3-month blinded and randomized controlled trial (RCT) designed to compare the effects of two community pedometer-based walking interventions (reflecting these separate and combined messages) relative to a control group on blood pressure in sedentary/low active post-menopausal women, a population at increased risk of cardiovascular disease. 120 sedentary/low active post-menopausal women (45-74 years of age) will be randomly assigned (computer-generated) to 1 of 3 groups: A) 10,000 steps/day (with no guidance on walking intensity/speed/cadence; BASIC intervention, n = 50); B) 10,000 steps/day and at least 30 minutes in moderate intensity (i.e., a cadence of at least 100 steps/min; ENHANCED intervention, n = 50); or a Control group (n = 20). An important strength of the study is the strict control and quantification of the pedometer-based physical activity interventions. The primary outcome is systolic blood pressure. Secondary outcomes include diastolic blood pressure, anthropometric measurements, fasting blood glucose and insulin, flow mediated dilation, gait speed, and accelerometer-determined physical activity and sedentary behavior. This study can make important contributions to our understanding of the relative benefits that walking volume and/or intensity may have on blood pressure in a population at risk of cardiovascular disease. ClinicalTrials.gov Record NCT01519583, January 18, 2012

Effects of Weight Loss and Exercise on GlycA Levels in Middle-Aged Adults

GlycA is a novel inflammatory biomarker that measures systemic inflammation. Inflammation accompanies atherosclerosis, leading to cardiovascular disease (CVD). The effects of a combined exercise-plus-diet intervention on GlycA levels is not well-versed in the current literature. The purpose of this study was to evaluate the effects of weight loss and exercise on GlycA levels in obese adults, to investigate potential mediators that contribute to GlycA reduction, and to determine a possible association between GlycA and the well-established CRP. GlycA, body composition, fitness, and blood lipids were measured in 30 sedentary, overweight and obese adults (30-65 years) before and after the weight loss intervention. Participants underwent The Prescribed Exercise to Reduce Recidivism After Weight Loss Pilot (PREVAIL-P) study's 10-week combined intervention of aerobic treadmill exercise (2-3 times/week for 30-50 minutes) and an OPTIFAST diet regimen to achieve a clinically significant weight loss (CWL) of 7%. Baseline GlycA was associated with CRP (r = 0.61, p=0.001), insulin (r = 0.41, p = 0.031), absolute VO2 (r= -0.40, p=0.030), relative VO2 (r = -0.46, p = 0.01), and fat mass (r = 0.46, p = 0.011), but was not associated with BMI, total cholesterol, HDL, LDL, triglycerides, or glucose levels (all ps < 0.05). The 10-week combined intervention significantly reduced GlycA (mean [delta]: -27.9 [plus-minus] 15.2 [mu]956;mol/L, p[less=than]0.05), but not CRP (mean [delta]: -0.3 [plus-minus] 0.8 mg/dL, p=0.41). Significant improvements in body compositional, fitness, and blood lipid variables did occur. However, changes in GlycA were not significantly correlated with changes in our suspected mediators. The current study effectively reduced weight and GlycA levels, indicative of better health scores; however, the mediators of GlycA's change still remain unknown

Effects of Weight Loss and Exercise on GlycA Levels in Middle-Aged Adults

GlycA is a novel inflammatory biomarker that measures systemic inflammation. Inflammation accompanies atherosclerosis, leading to cardiovascular disease (CVD). The effects of a combined exercise-plus-diet intervention on GlycA levels is not well-versed in the current literature. The purpose of this study was to evaluate the effects of weight loss and exercise on GlycA levels in obese adults, to investigate potential mediators that contribute to GlycA reduction, and to determine a possible association between GlycA and the well-established CRP. GlycA, body composition, fitness, and blood lipids were measured in 30 sedentary, overweight and obese adults (30-65 years) before and after the weight loss intervention. Participants underwent The Prescribed Exercise to Reduce Recidivism After Weight Loss Pilot (PREVAIL-P) study's 10-week combined intervention of aerobic treadmill exercise (2-3 times/week for 30-50 minutes) and an OPTIFAST diet regimen to achieve a clinically significant weight loss (CWL) of 7%. Baseline GlycA was associated with CRP (r = 0.61, p=0.001), insulin (r = 0.41, p = 0.031), absolute VO2 (r= -0.40, p=0.030), relative VO2 (r = -0.46, p = 0.01), and fat mass (r = 0.46, p = 0.011), but was not associated with BMI, total cholesterol, HDL, LDL, triglycerides, or glucose levels (all ps &lt; 0.05). The 10-week combined intervention significantly reduced GlycA (mean [delta]: -27.9 [plus-minus] 15.2 [mu]956\;mol/L, p[less=than]0.05), but not CRP (mean [delta]: -0.3 [plus-minus] 0.8 mg/dL, p=0.41). Significant improvements in body compositional, fitness, and blood lipid variables did occur. However, changes in GlycA were not significantly correlated with changes in our suspected mediators. The current study effectively reduced weight and GlycA levels, indicative of better health scores\; however, the mediators of GlycA's change still remain unknown