No abstract is provided for this article.
No abstract is provided for this article.
Overweight and obesity are not homogeneous phenotypes as individuals differ in terms of the regional distribution of the excess weight or fat. Overweight and obesity are also complex multifactorial phenotypes influenced by both genetic and nongenetic determinants. Heritability of fat mass or percent body fat derived from underwater weighing measurement reaches about 25% of the age and gender adjusted phenotypic variance. Based on twin and parent-child data, it has been reported that the heritability of resting metabolic rate, thermic response to food, and energy cost of submaximal exercise, adjusted for the proper concomitants, is as high as 40%. The level of habitual physical activity also exhibits a significant heritability level on the order of about 25%. Experimental overfeeding with identical twins demonstrates that there are inherited differences in body weight and body composition response. The most important factor identified thus far to account for the individual differences in response to long-term overfeeding is a nutrient partitioning characteristic, namely the proportion of fat vs lean tissue gained. The high gainers are those storing energy primarily in the form of fat, while the low gainers are storing relatively more in the form of lean tissue.
PURPOSE: Investigate the effects of Cytomegalovirus (CMV) serostatus on measures of physical (VO2max) and metabolic (Insulin Sensitivity) fitness in healthy adults before and after a 20-week exercise intervention. METHODS: Serum samples from a subsample (n=120) of the HERITAGE study (Bouchard et al., MSSE 1995) were analyzed for CMV serostatus. This subset was selected from the 60 men and 60 women with the greatest VO2 max increase in response to the 20 week intervention and included Caucasians (n=82) and African Americans (n=38). Baseline VO2max was assessed using a stationary cycle ergometer test and insulin sensitivity was measured using a 3-hour intravenous glucose tolerance test before and after the training program. RESULTS: Caucasians had a lower prevalence of CMV seropositive status than African-American (33% vs. 68%, p<001). In Caucasians, CMV serostatus was not associated with baseline aerobic capacity or insulin sensitivity. In African-Americans, CMV seropositive status was associated with impaired aerobic capacity pre- (2.39 ± .53 L/min vs 1.84 ± .67 L/min; p=.020; CMV seropositive vs CMV seronegative) and post-intervention (2.44 ± .75 L/min vs 3.03 ± .59 L/min; p=.028). Significant effects of CMV serostatus persisted after controlling for age, sex, body weight, and body fat percentage (p=.047, p=.047; pre- and post-intervention resp.). African-American CMV seropositive participants also had higher insulin responses to an IVGTT both pre- (1971.64 ± 1173.31 10 min.mU-1.mL-1 vs 849.16 ± 456.67 min.mU-1.mL-1; p=.014) and post-intervention (1873.88 ± 1212.65 min.mU-1.mL-1 vs 909.18 ± 432.38 min.mU-1.mL-1; p=.038). CMV serostatus still had significant effects on insulin sensitivity after controlling for age, sex, and aerobic capacity (p=.011, p=.016; pre- and post-intervention, resp.). CONCLUSIONS: In sedentary African American adults, CMV serostatus is significantly associated with lower VO2max and insulin sensitivity even while controlling for variables known to mediate fitness and glucose sensitivity, and the associations persisted after exposure to 20 weeks of a standardized exercise program. We conclude that CMV status is another personal characteristic that needs to be taken into account in the assessment of cardiorespiratory fitness and insulin sensitivity in this population.
The study of the role of genetic variation on energy intake and nutrient intake is broad and has considerable public health implications. Genetic differences influence behavioral and biological affectors of food intake. They are also thought to impact on several nutritionally influenced risk factors (e.g., dyslipoproteinemia) and morbid conditions (e.g., diabetes). These issues have been the topic of much research in the past few decades, as evidenced by the multiple review articles cited in this section. In the behavioral domain, the questions are relatively simple. Do genes determine eating behaviors such as how much one eats, preferences for certain types of foods, and frequency or pattern of eating? The current research suggests that there is resemblance among family members for these behaviors, although it is unclear if they are determined by genes, shared environments, or both.
