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RESEARCH PRODUCT

Age-related decline in body cell mass in elderly men and women, determined by a noninvasive nuclear technique: Effects of physical activity and dietary potassium intake

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The body cell mass (BCM) represents the actively metabolizing cellular components of the human body. In this study, the hypothesis was tested that physical activity and a sufficient dietary intake of potassium attenuate the age-related decline in BCM in the elderly. Cross-sectional data were collected in 82 male and 79 female non-institutionalized elderly (60–90 years) from Mainz, Germany, and were analyzed by age groups. BCM was calculated from total body potassium, measured by whole-body counting of naturally occurring 40K. Physical activity level (PAL) was assessed by a standardized questionnaire. Dietary intake of potassium (DIP) was estimated from a 7-day food diary. The results showed the following trends: (1) BCM decreased continuously from age 60 to 90 years by 11.2% (men) and 7.0% (women). BCM was inversely correlated with age in both sexes (men, P < 0.001; women, P < 0.05), but significant age group differences only existed for men (P < 0.01, one-way analysis-of-variance). Women had less BCM than men in all age groups (P < 0.001, t tests). (2) Correlation analyses demonstrated that in both sexes PAL declined with advancing age (P < 0.05), whereas DIP did not change significantly with age. (3) In both sexes, BCM showed a strong positive correlation with PAL (P < 0.001), but did not correlate significantly with DIP. Multiple linear regression analysis (independent variables were PAL, DIP, age, height, weight) demonstrated that PAL, age, and height explained 45% of the variability in BCM in men. In women, PAL was the only significant predictor of BCM, explaining 23% of the variance. The study supports the hypothesis that the level of physical activity is associated with the decline of BCM in the elderly. Am. J. Hum. Biol. 13:204–211, 2001. © 2001 Wiley-Liss, Inc.