Because of the uncertainty as to the extent to which cardiac size is determined by exercise training vs genetic endowment, this study investigated familial (genetic plus common family environment) vs nonfamilial influences on cardiac size. College-age monozygotic twins (group 1, 31 sets), dizygotic twins (group 2, 10 sets), siblings of like sex (group 3, six sets), and nonrelated subjects (group 4, 15 sets) underwent echocardiographic and electrocardiographic tests, measurement of maximum oxygen uptake (VO2max), and evaluation of pulmonary and body composition; mean intrapair differences of the four groups were compared. Mean intrapair differences in cardiac size varied as much for subjects in group 1 as for those in groups 2 and 3. However, subjects in groups 1, 2, and 3 had less variation (p < .

Obesity-associated metabolic illnesses are increasing at an alarming rate in Asian countries. A common feature observed in the Asian population is a higher incidence of abdominal obesity—the “skinny-fat” Asian syndrome. In this review, we critically evaluate the relative roles of genetics and environmental factors on fat distribution in Asian populations. While there is an upward trend in obesity among most Asian countries, it appears particularly conspicuous in Malaysia. We propose a novel theory, the Malaysian gene-environment multiplier hypothesis, which explains how ancestral variations in feast-and-famine cycles contribute to inherited genetic predispositions that, when acted on by modern-day stressors—most notably, urbanization, westernization, lifestyle changes, dietary transitions, cultural pressures, and stress—contribute to increased visceral adiposity in Asian populations. At present, the major determinants contributing to visceral adiposity in Asians are far from conclusive, but we seek to highlight critical areas for further research.

Healthy male monozygotic (MZ) and dizygotic (DZ) twin pairs (MZ pairs = 77; DZ pairs = 88) were studied to assess the effect of dietary intake, physical activity, physical fitness, body mass index (BMI), sum of the triceps and subscapular skinfold measurements, alcohol and caffeine consumption, and smoking patterns on blood pressure. Data on physical activity, detailed dietary intake, medical history, and demographics were obtained from a questionnaire. A bicycle ergometer was used to estimate level of fitness; other medical information was ascertained from physical examination. After normalizing the study variables, intraclass correlations for BMI and the sum of the triceps and subscapular skinfold measurements were higher in MZ than in DZ twin pairs (BMI: MZ r = 0.76, DZ r = 0.48; skinfolds: MZ r = 0.73, DZ r = 0.28), as were VO2max(MZ r = 0.63, DZ r = 0.25) and post-bike heart rate (MZ r = 0.69, DZ r = 0.19). Both systolic (SBP) and diastolic blood pressure (DBP) had high heritability estimates (SBP = 0.60, and DBP = 0.66). Using factor analysis, four major lifestyle factors were identified and categorized as: 1) dietary intake; 2) a factor heavily weighted by cigarette smoking, alcohol and caffeine consumption; 3) fatness; 4) physical activity and physical fitness. Adjustment for these factors did not alter heritability estimates for either SBP or DBP.