Body Composition: Children and Maturation

1. Body Composition: Children and Maturation Chapters 8 and 9

2. Total Body Composition • Birth to Old Age • The human body goes through many changes when aging

3. Infant

4. Child

5. Teens

6. Young Adults

7. Middle-aged

8. Parents

9. Seniors

10. Maturation • During childhood and adolescence, FFB density progressively increases. • As children age, the hydration of the FFB decreases and the mineral content increases.

11. Maturation • The classic 2-C models systematically overestimate %BF of children and adolescents. • Either the 4-C or 3-C (water) models should be used to obtain reference measures of body composition for children and adolescents.

12. Maturation • The overall density of the FFB tends to decrease with aging primarily due to the loss of bone mineral and skeletal muscle mass.

13. Maturation • There is a wide degree of inter-individual variability in the FFB composition of older men and women.

14. Maturation • The classic 2-C models systematically overestimates the average %BF for groups of older adults.

15. Newborns • Muscle comprises... • 27% N • 33% K • 28% water • ...of body’s total stores.

16. Newborn • Has a much smaller muscle mass than the adult, about 25% versus 40% of body weight.

17. Newborns • At birth, boys and girls do not differ in water, fat, protein, and osseous and non-osseous mineral contents. • In fact, data indicate marked similarity between males and females at one month of age.

18. Infants • Changes in body components include an 8 to 9% increase in fat mass to a level of 22 to 24% at one year of age and a more than two-fold increase in FFM.

19. Infants • The most notable change in the constituents of FFM is a large shift of water between the ECF (extracellular fluid) and the ICF (intracellular fluid) compartments, although there is only a slight increase in TBW (1-2%).

20. Childhood, Puberty, and Adolescence • Childhood - period from infancy (ends at 1 yr) to puberty. • Puberty - state of physical development when sexual reproduction first becomes possible. • Adolescence - includes puberty and continues until sexual maturation is complete.

21. Childhood, Puberty, and Adolescence • Sex differences appear during childhood. • By the age of 5, bone mineral has increased from 3 to 3.6% of FFM in boys, but not in girls. • %BF tends to be lower in boys (14.6%) than in girls (16.7%).

22. Childhood, Puberty, and Adolescence • There is little or no change in %BF for girls from 10 to 18 years, although total fat mass increases at an annual rate of 1.14 kg per year.

23. Childhood, Puberty, and Adolescence • For boys, %BF decreases annually by 1.15% across the age range.

24. Childhood, Puberty, and Adolescence • The water content of FFM is about 75% and 77% for boys and girls respectively.

25. Childhood, Puberty, and Adolescence • There are gender differences during adolescence in the growth of FFM. • From 10 to 20 yrs, FFM increases by 33 kg in boys, but only 16 kg in girls.

26. Childhood, Puberty, and Adolescence • The increase in FFM continues for a longer period in males than in females; adult levels are reached at 18 yrs in females, but not until about 20 yrs in males.

27. Childhood, Puberty, and Adolescence • The major changes in the composition of FFM from pubescence to adulthood occur in the water and mineral portions.

28. Childhood, Puberty, and Adolescence • These changes show that a multi-component model is necessary in children and adolescents for the estimation of body composition from body density.

29. Young, Middle-Aged, and Older Adults • From 20 to 55 years of age, changes in body composition are slower compared with those during childhood, adolescence, or senescence.

30. Young, Middle-Aged, and Older Adults • It has been demonstrated that the average individual in this country will gain approximately one pound of additional weight each year after the age of 25 years.

31. Young, Middle-Aged, and Older Adults • Such a seemingly small gain, however, results in 30 pounds of excess weight by the age of 55 years.

32. Young, Middle-Aged, and Older Adults • Since the bone and muscle mass decrease by approximately one half pound per year due to reduced physical activity, fat is actually increasing by 1.5 pounds per year.

33. Young, Middle-Aged, and Older Adults • This means a 45 pound gain in fat over this 30 year period!

34. Young, Middle-Aged, and Older Adults • BMC increases about 8% per year until adolescence. • After adolescence the rate of increase in BMC is slower in girls than in boys but continues until a peak BMC of 1000 g is attained by women at 30-39 years.

35. Young, Middle-Aged, and Older Adults • In women aged 50-99 years, BMC decreases at a rate of 6-7% per decade.

36. Young, Middle-Aged, and Older Adults • Males achieve adult mineralization by the age of 20 years with an average BMC of 1307 g, which remains constant from 50-60 years.

37. Young, Middle-Aged, and Older Adults • A decrease in BMC in males begins between 60 and 70 years; the rate of decrease is about 10% from 70-85 years.

38. Young, Middle-Aged, and Older Adults • For women and men up to 70 yrs. of age, calcium and potassium are lost proportionally.

39. Young, Middle-Aged, and Older Adults • In men older than 70 years, the TBCa/TBK ratio is higher, indicating a greater loss of muscle mass than of bone mineral content.

40. Young, Middle-Aged, and Older Adults • The non-muscle lean mass, mainly vital organs, does not change with age; total body protein (TBP) decreases 17% between ages 20 and 79 yrs.

41. Young, Middle-Aged, and Older Adults • Adults, like children and adolescents, change in body composition, but the changes during adulthood are slower.

42. Young, Middle-Aged, and Older Adults • Some of these changes affect the composition of FFM and thereby alter its density.

43. Young, Middle-Aged, and Older Adults • There is a lack of research literature concerning assessments of body composition by multiple models among ethnic groups.

44. Young, Middle-Aged, and Older Adults • Most of our knowledge of changes in total body composition has been inferred from cross-sectional data, which can show the mean changes but not individual variation.

45. Assessing Body Composition • The skinfold equations recommended for children include the Lohman equation (7-17yrs) and the Slaughter equation (8-17yrs) • Information on these equations can be found in Table 8.1, p. 113.

46. Assessing Body Composition • Ethnic specific SKF equations have been developed for American Indian, African American, and Caucasian Children. • Additional cross-validation studies are needed to confirm the accuracy of these equations for estimating %BF

47. Assessing Body Composition • The Slaughter SKF equations provide a fairly reasonable estimate of average %BF for groups of African American and Caucasian children and adolescents; however, for individuals the prediction error is between + 8-10% BF.

48. Assessing Body Composition • The Houtkooper BIA equation provides a fairly good estimate of body composition for groups of Caucasian children and adolescents; the error for individuals may be as large as + 11% BF.

49. Assessing Body Composition • Compared to HW, ADP overestimates the average Db of children.

50. Assessing Body Composition • DEXA typically underestimates average %BF in older adults. • Preliminary findings suggest that HW and ADP yield similar estimates of Db for groups of older men and women.