Regional Body Composition
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- 1.Regional Body Composition Sex and Ethnic Variation Chapter 18
2. Regional Body Composition
- Regional body composition refers to variation in the anatomical distribution of the major components of the body mass:
- adipose tissue,
- skeletal muscle,
- and skeletal tissues.
3. Regional Body Composition
- The termdistributionrefers to the absolute or relative amount of a tissue in different regions or compartments of the body.
- The termpatterningis also used in discussion of regional body composition.
4. Variation in Body Composition
- Two major sources of variation in body composition are the biological sex of the individual and population affinity (ethnicity).
5. Regional Body Composition
- Knowledge of age-, sex-, maturity-, and ethnicity-associated variation in regional body composition should contribute to the understanding of human variability.
6. Regional Body Composition
- A major portion ofthe variability in body composition has its origins during the years of growth and maturation.
7. Sex Differences
- Biological difference between the sexes influence body composition per se and processes that affect body composition:
- Rate of growth and maturation
- The timing and tempo of the adolescent growth spurt and sexual maturation
- Body proportions and physique
8. Sex Differences
- Sex differences in body composition are apparent early in life, are magnified during the adolescent growth spurt and sexual maturation, and present through adulthood.
9. Regional Body Composition
- Relatively greater accumulation of subcutaneous adipose tissue on the trunk compared to the extremities is often described as acentral or truncal pattern .
10. Truncal Adiposity 11. Regional Body Composition
- A relatively greater accumulation over the abdomen compared to that over the hips is described as anandroidpattern, while the reverse is labeled agynoidpattern.
12. Regional Body Composition
- Abdominal fatness is often indicated as a significant determinant of the relationship between obesity and morbidity, and as an independent risk factor for several degenerative diseases of adulthood, most notably some cardiovascular diseases and non-insulin-dependent diabetes.
13. Adipose Tissue
- Adipose tissue can be differentiated into that which is visceral (internal or deep; VAT) and that which is subcutaneous (external or outer; SAT).
14. Age and Sex Differences
- After young adulthood, T skinfold thickness increases more than E skinfold thickness in males, while both T and E skinfold thicknesses increase by similar amounts through the fourth decade in females.
- Subsequently, T increases more than E in females.
15. Age and Sex Differences
- The T/E ratio does not differ between the sexes from late childhood into early adolescence.
- The ratio is rather stable in females, but increases considerably in males during adolescence and more slowly through the fifth decade.
16. Age and Sex Differences
- Thus, males have proportionally more SAT on the T than E during adolescence and into adulthood.
17. Ethnic Variation
- There are strong links between ethnicity, obesity, and disease.
- Although individuals are labeled as belonging to a particular racial or ethnic group, variation within each of the categories is considerable.
18. Ethnic Variation
- Certain ethnic groups have a relatively higher risk for obesity, predisposing them to cardiovascular disease, hypertension, non-insulin-dependent diabetes, certain cancers, and osteoarthritis.
19. Ethnic Variation
- Because of this, African American women, Hispanic women, and American Indian women and men have been targeted for weight loss in nationwide health promotion and disease prevention initiatives.
20. Ethnic Variation
- Among males, the T/E ratio does not consistently differ between White and Hispanic American children and adolescents.
21. Ethnic Variation
- Subsequently, it is consistently larger in Hispanic Americans through adulthood.
22. Ethnic Variation
- In contrast, the ratio is slightly but consistently larger in African Americans during childhood and adolescence.
23. Ethnic Variation
- It is also larger in African Americans than in Whites during adulthood, but slightly smaller in African Americans than Hispanic Americans from the third through fifth decades.
24. Ethnic Variation
- This suggests that, among males, African Americans have proportionally more SAT on the T than E during childhood through young adulthood than Whites and Hispanic Americans.
25. Ethnic Variation
- The T/E ratio is thus, on average, consistently larger in African American and Hispanic American males than in White males throughout adulthood.
26. Ethnic Variation
- During adulthood, African American women and Hispanic American women increase in both skinfold thicknesses more than White women, and these increases are larger at the subscapular site than at the triceps site.
27. Ethnic Variation
- Hence the T/E ratio is consistently larger in women from these two ethnic groups, indicatingproportionally more SAT on the T.
28. Ethnic Variation
- The ethnic difference is greater in females than in males due especially to larger trunk skinfold thicknesses in Hispanic American women.
29. Ethnic Variation and Assessment
- Ethnic differences in fat patterning and body composition place into question the applicability of generalized field method prediction equations derived primarily from Caucasian samples.
30. Ethnic Variation and Assessment
- Because of differences in the proportions of the FFB composition among ethnic groups and inter-individual differences within ethnic groups, multi-component body composition assessment is recommended as a reference measure.
31. Ethnic Variation and Assessment
- Unfortunately, most studies evaluating the applicability of methods and equations for specific ethnic groups have not used multi-component models.
32. Sex Variation
- Adolescent girls have relatively little VAT, which suggests that abdominal VAT accumulates in later adolescence.
33. Sex Variation
- During adulthood, abdominal VAT increases with age in each sex, more so in males than in females.
34. Sex Variation
- Abdominal SAT also increases with age to about 60 years, and then decreases in each sex; females have, on average, more more SAT than males.
35. Sex Variation
- Males have proportionally more abdominal VAT than females and the sex difference increases with age.
- Women gain relatively more abdominal VAT after menopause.
36. Maturational Variation
- Early maturing males have relatively more SAT on the T than average and late maturing males not only during adolescence but also in adulthood, which suggests persistence of maturity-associated variation into adulthood.
37. Maturational Variation
- Thus, for the same size and mass, early maturing males have proportionally more SAT as adults.
38. Maturational Variation
- There appears to be a gain in overall fatness and SAT during the transition from the premenarcheal to the postmenarcheal state.
- Proportionally more SAT is accumulated on the T than on E at this time.
39. Maturational Variation
- After menarche, proportionally more VAT is accumulated (lower SAT/FM ratio), while the relative distribution of SAT is unchanged (similar T/E ratios).
- The dry, defatted skeleton weighs, on average, about 95g in infant boys and slightly less in girls.
- In young adulthood, the skeleton weighs about 4.0 kg in men and 2.8 kg in women.
- As a percentage of body weight, the dry, fat-free skeleton comprises about 3% of body weight in the fetus and newborn and about 6-7% of body weight in the adult.
- Bone mineral, estimated from ash weight, comprises about 2% of body weight in infants and 4-5% of body weight in adults.
- The skeleton is consistently heavier and has more mineral in American Blacks than in Whites from infancy through adulthood.
- Long bones are more dense than vertebrae.
- Cervical vertebrae are more dense than the other vertebrae in males but not significantly so in females.
- Bones of males are more dense than those of females.
- Bones of American Blacks are more dense than those of American Whites.
- Densities of individual bones in males and females of both ethnic groups decrease with age.
- The sex differences in density are related to bone mineral.
- There is an absence of sex differences in BMC and BMD fro