FAT AND FAT FREE BODY COMPOSITION IN OLDER MEN AND WOMEN

Accurate estimation of body composition in middle-aged and elderly
individuals is limited by a lack of knowledge of the fat free body (FFB)
composition in this age group. Currently available techniques are indirect
and usually based on FFB composition of young adults. When applied to
other age groups a constant FFB composition in all groups must be assumed.
However, reductions in bone mineral content and body potassium with
increasing age are well documented, with concommitant and significant
reductions in FFB density. The limited available evidence suggests body
water also declines with age. Consequently, the assumption of constant FFB
composition in different groups is invalid for the older population, and
errors of estimation of percent body fat as high as five percent can occur
when methods developed on young adults are applied to the older
population. Hence, the purpose of the proposed research will be to
quantify the fat free body composition of sedentary and physically active
men and women so that more accurate estimates of body composition can be
developed for these age groups for such methods as densitometry,
hydrometry, anthropometry, and total body electrical impedance. Two
hundred and forty men and women, aged 40-80 years, will be tested over
three years. Both sedentary and active subjects will be studied to test
the hypothesis that activity history, in addition to age and gender, is an
important determinant of body composition. All subjects will be measured
for total body water, bone mineral content, body density, selected
skinfolds and anthropometric dimensions, and total body electrical
impedance. Bone mineral content will be measured using single and dual
photon absorptiometry with measurements made at four sites on the forearm,
spine and femur giving a better estimate of mineral than has previously
been obtained. The subjects will be grouped by age, gender and physical
activity level, and the data analyzed for group differences. Multiple
regression prediction equations will be developed for estimation of fat and
fat free body emphasizing a multiple component approach with body water,
mineral content and body density as important components. Also, with
knowledge of the fat free body water and mineral content, fat free body
density may be estimated, making possible the development of improved two
component equations for estimation of body fat from body density and the
skinfold-body density relationship in the middle-aged and older
populations. The results will have important clinical and field
application in diverse areas concerned with nutritional assessment and
epidemiological investigation of health and fitness, as well as research
studies investigating body composition and functional capacity of
middle-aged and older men and women.