Iris A. Lesser

The effect of obesity on the association between liver fat and carotid atherosclerosis in a multi-ethnic cohort

OBJECTIVE Non-alcoholic fatty liver disease is the most common liver disorder in Western society, increasing in parallel with obesity and the metabolic syndrome. Evidence suggests that there is an independent relationship between liver fat (LF) and atherosclerosis, however it is unknown if this applies to low risk populations. The purpose of this study was to evaluate the association between LF and measures of sub-clinical carotid atherosclerosis in men and women of Aboriginal, Chinese, European, and South Asian origin. METHODS AND RESULTS Healthy men and women were assessed for LF (computed tomography scan) and atherosclerosis (carotid ultrasound) in addition to cardiovascular risk factors, demographics, and body composition. Liver Hounsfield units (HU) values were negatively correlated with age, BMI, waist circumference (WC), percent body fat, carotid intima media thickness total plaque area, and total area. LF was significantly associated with carotid IMT and total area after adjustment for sex, age, ethnicity, education, income and smoking status. However after adjusting for BMI and WC, LF was no longer significantly associated with atherosclerosis. CONCLUSION Increased LF may be associated with atherosclerosis, however, after adjustment for body composition, LF was not significantly associated with sub-clinical atherosclerosis. BMI and WC are useful anthropometric measures for the evaluation of CVD risk independent of LF.

A Cross-Sectional Analysis of the Association between Physical Activity and Visceral Adipose Tissue Accumulation in a Multiethnic Cohort

Higher levels of VAT at the same body size and lower levels of physical activity (PA) have been reported in persons of Chinese and South Asian origin compared to European origin. The purpose of this study was to test the hypothesis that higher levels of VAT in persons of Chinese and South Asian origin versus European origin are associated with lower levels of PA. Chinese, European, and South Asian participants were assessed for sociodemographics, obesity-related measures, anthropometrics, and PA. Bivariate correlations, analysis of covariance, and regression models were used to explore ethnic differences in PA and the role of PA in explaining obesity-related measures. We observed ethnic differences in both body fat distribution and PA. Chinese and South Asians had higher amounts of VAT at a given BMI but lower amounts of moderate PA, vigorous PA, and moderate-to-vigorous PA (MVPA). Furthermore, we found ethnic-specific differences in the associations between body fat distribution and PA with only Europeans showing a consistent negative relationship between body fat distribution and PA. When ethnic differences in PA were taken into account, there were no longer any differences in VAT between the Chinese and European groups, while VAT remained higher in South Asians than Europeans.

The effect of body fat distribution on ethnic differences in cardiometabolic risk factors of Chinese and Europeans.

This study aimed to examine the differences in body fat distribution and cardiometabolic risk between individuals of Chinese and European origin and the role of body fat distribution on ethnic differences in cardiometabolic risk. A total of 418 participants from the Multicultural Community Health Assessment Trial were assessed for visceral adipose tissue (VAT), subcutaneous abdominal adipose tissue (SAT), anthropometric variables, blood pressure, and lipid, insulin, and glucose levels. Multiple regression analyses were split by sex and adjusted for appropriate covariates in model 1a and further adjusted for VAT in model 1b or SAT in model 1c. A secondary model replaced body mass index (BMI) with waist circumference (WC). Chinese males had higher levels of triglycerides, insulin, homeostasis model assessment, and SAT than European males, as well as higher total cholesterol (TC), glucose, and VAT in the model adjusted for WC. Chinese females had higher glucose levels than European females after adjustment for either BMI or WC. When VAT was added to the models, differences in cardiometabolic risk factors remained significant but were attenuated between Chinese and European males and females; SAT did not attenuate the ethnic difference in cardiometabolic risk. These findings suggest that the higher VAT levels seen in the Chinese population do not fully account for the ethnic disparities in these risk factors. Given the observed interethnic difference in body composition, current BMI and WC cutoffs might be misleading when it comes to identifying Chinese individuals at risk for type 2 diabetes or cardiovascular disease.

Effectiveness of Exercise on Visceral Adipose Tissue in Older South Asian Women.

INTRODUCTION Individuals of South Asian (SA) origin have a greater risk for type 2 diabetes and cardiovascular disease than other ethnic populations. This increased risk is in part explained by the unique obesity phenotype of elevated visceral adipose tissue (VAT) among this population. Aerobic exercise in Europeans is effective at reducing VAT, but this has not been studied in SA, who have some of the lowest levels of physical activity in the world. Therefore, the purpose of this study was to determine whether exercise can reduce VAT given the unique obesity phenotype and associated disease risk in the SA population. METHODS A total of 75 physically inactive, postmenopausal SA women were randomized to either culturally based (Bhangra dance), standard (gym-based), or control (nonexercise) program for 12-wk. The primary outcome was change in VAT. RESULTS The average attendance in the culturally based and standard program was 78% ± 33% and 67% ± 25%, respectively. After an intention-to-treat analysis, VAT was not significantly reduced in culturally based (-60 cm, 95% confidence interval [CI] = -172 to 54, P = 0.300) or standard (-98 cm, 95% CI = -216 to 21, P = 0.106) exercise compared with control after adjustment for baseline physical activity and age. In those participants who attended more than two-thirds of the exercise classes, VAT was significantly reduced compared with control (-109 cm, 95% CI = -204 to -13, P = 0.026). CONCLUSION In intention-to-treat analysis VAT was not significantly reduced after 12 wk of either standard or culturally based exercise. However, attendance in both standard and culturally based exercise was high, and VAT was significantly reduced among SA women who adhered to these programs.

Association between exercise-induced change in body composition and change in cardiometabolic risk factors in postmenopausal South Asian women

The South Asian population suffers from a high prevalence of type 2 diabetes and cardiovascular disease (CVD). A unique obesity phenotype of elevated visceral adipose tissue (VAT) is associated with CVD risk among South Asians. Exercise-induced reduction in VAT and body fat is an effective mechanism to improve cardiometabolic risk factors but this has not been shown in South Asians. Whether exercise-induced changes in measurements such as waist circumference (WC) are independently related to changes in cardiometabolic risk factors in South Asians is unknown. Multi-slice computed tomography scanning was used to assess VAT, cardiometabolic risk factors through a fasting blood sample, and body fat using dual-energy X-ray absorptiometry. Forty- nine postmenopausal South Asian women who participated in two 12-week aerobic exercise programs were included. Bivariate correlations were used to assess associations between change in cardiometabolic risk factors and change in body composition. Regression analyses were conducted with change in glucose, insulin, and homeostatic model assessment of insulin resistance (HOMA-IR) as dependent variables and change in body composition as independent variables of interest. There were significant associations between changes in fasting insulin, glucose, and HOMA-IR with change in VAT. The association between change in VAT and these cardiometabolic risk factors was independent of change in other body composition variables of interest. South Asian women should be encouraged to engage in aerobic activity to reduce their risk of type 2 diabetes and CVD, and physicians should be aware of improvements in glucose regulation with exercise training not observed through reductions in WC.

The Association Between Cardiorespiratory Fitness and Abdominal Adiposity in Postmenopausal, Physically Inactive South Asian Women

In South Asians, a unique obesity phenotype of high abdominal fat is associated with increased cardiovascular risk. Low cardiorespiratory fitness (CRF) is associated with abdominal fat and an increased risk of cardiovascular disease. The purpose of this paper is to determine whether CRF as assessed by VO2 peak, in post-menopausal South Asian women, was associated with body fat distribution and abdominal fat. Physically inactive post-menopausal South Asian women (n = 55) from the Greater Vancouver area were recruited and assessed from January to August 2014. At baseline, VO2 peak was measured with the Bruce Protocol, abdominal fat with CT imaging, and body composition with dual energy X-ray absorptiometry. ANOVA was used to assess differences in subcutaneous abdominal adipose tissue (SAAT), visceral adipose tissue (VAT) and total abdominal adipose tissue (TAAT) between tertiles of CRF. Bivariate correlation and multiple linear regression analyses explored the association between VO2 peak with SAAT, VAT, TAAT and body composition. Models were further adjusted for body fat and body mass index (BMI). Compared to women in the lowest tertile of VO2 peak (13.8–21.8 mL/kg/min), women in the highest tertile (25.0–27.7 mL/kg/min) had significantly lower waist circumference, BMI, total body fat, body fat percentage, lean mass, SAAT, VAT and TAAT (p < 0.05). We found VO2 peak to be negatively associated with SAAT, VAT and TAAT, independent of age and body fatness but not independent of BMI. Further research is necessary to assess whether exercise and therefore improvements in CRF would alter SAAT, VAT and TAAT in post-menopausal South Asian women.

The association between physical activity and liver fat after five years of follow-up in a primary prevention multi-ethnic cohort.

OBJECTIVE Excess liver fat (LF) is associated with dyslipidemia, insulin resistance and cardiovascular disease. Evidence suggests that there is an independent relationship between physical activity (PA) and LF although little is known of the role of PA intensity in reducing LF. The purpose was to evaluate whether meeting PA guidelines, the amount of PA and the intensity of PA at baseline were associated with LF after five-years. METHODS Men and women (n=478) living in Vancouver, Canada of Aboriginal, Chinese, European or South Asian background completed baseline measurements in 2004-2005. Liver fat was assessed using CT scans at 5-year follow-up, and PA using a PA questionnaire at baseline as well as demographics and anthropometry. RESULTS In separate unadjusted models, meeting moderate-vigorous PA (MVPA) guidelines (p=0.009), vigorous PA (p=0.002) and MVPA (p=0.017) but not moderate PA (p=0.068) was predictive of LF at five years (p=0.009). In multiple linear regression models, when adjusted for covariates, meeting MVPA guidelines and MVPA with LF at five years was no longer significant (p>0.05) while vigorous PA remained significant (p=0.021). CONCLUSION Meeting PA guidelines through MVPA may not be adequate to prevent the accumulation of LF and PA guidelines may require revision. Vigorous PA should be encouraged to prevent LF accumulation.

The effects of a delay following warm-up on the heart rate response to sudden strenuous exercise.

Introduction: Sudden strenuous exercise (SSE) has previously been shown to result in electrocardiograph (ECG) abnormalities indicative of myocardial ischemia when not preceded by a warm-up. Athletes regularly undergo SSE and are often unable to warm-up immediately prior to competition. It is unknown whether a delay post warm-up will result in the same heart rate (HR) response to SSE as seen with no warm-up. Aims: To compare the HR response and to observe for ECG abnormalities during SSE with a warm up, with a delay after warm up and without a warm up. Methods: Seven male subjects randomly completed three SSE exercise conditions while being monitored by ECG; a 15 second supramaximal sprint following three conditions: no warm up (NW); Original Research Article Lesser and Hodges; BJMMR, 8(9): 765-771, 2015; Article no.BJMMR.2015.504 766 immediately following a warm-up (WU); and following a 10-minute delay post warm up (D). There were no ECG abnormalities across any of the conditions indicative of myocardial ischemia. Results: Significant differences (p<0.05) were found in the HR response for all time periods during exercise between WU and NW, between WU and D, but not between D and NW. A delay between warm-up and SSE resulted in a lowered HR response to the SSE compared with a warm-up immediately preceding, but a higher HR response to SSE with no warm-up. Conclusion: The findings of this study suggest that a 10 minute delay following warm-up before SSE is too long to maintain the benefits of warm-up.

Characterization of aerobically fit individuals with cardiovascular disease.

Abstract With an ageing population there is an increased prevalence of individuals living with cardiovascular disease (CVD). Characteristics of older aerobically fit individuals with previously diagnosed CVD have not been studied. Therefore, our knowledge is limited as to how, or if, aerobically fit individuals with CVD attempt to adapt their physical activity and the intensity of their training programmes. The objective of this paper is to characterise the physical activity habits and behaviours of older aerobically fit individuals with CVD. We identified 28 aerobically fit patients with CVD from those who completed a minimum of 15 and 12 min of the Bruce treadmill protocol for men and women, respectively. Consenting participants responded to questionnaires regarding physical activity levels, competitive event participation and self-monitoring since diagnosis of heart disease. Average age and treadmill time of participants were 56 and 49 years and 15.6 and 13.0 min for males and females, respectively. Data were obtained regarding recent medical history (medical diagnoses, surgeries/procedures). Despite the majority of individuals participating in the same or more activity since their diagnosis, 25% indicated that their condition limited their activity and 39% reported having symptoms during activity. Nearly all participants (93%) indicated that they monitored their heart rate during exercise. However, only 14% of participants stated that their physician advised them on how to exercise safely. It is necessary for physicians and cardiac rehabilitation programmes to be involved in safe and effective exercise programming to allow individuals to return to sport after CVD.

A Review of Obesity and Body Fat Distribution and Its Relationship to Cardio-Metabolic Risk in Men and Women of Chinese Origin

Obesity is increasing in people of Chinese background whether in China or in other countries. The purpose of this review is to discuss the associations of obesity in men and women of Chinese background with cardio-metabolic risk with specific attention to body fat distribution. Evidence suggests that current BMI and WC targets may actually underestimate the cardio-metabolic risk in Chinese compared to European populations from which they were derived. Through a number of investigations, we and others have identified that Chinese men and women tend to have higher cardio-metabolic risk factors at a given body size than people of European background (from which guidelines are generally derived). Our additional investigations have indicated that Chinese men and women have greater amounts of VAT, but similar amounts of DSAT at a given body fat than Europeans and it may be the higher VAT in Chinese people that is, in part, responsible for the greater cardio-metabolic risk in the Chinese. Further investigation of this topic should prove fruitful in shedding light onto the determinants of body fat accumulation and distribution that may help to inform obesity prevention and treatment strategies.