Children’s Nutrition Research Center Staff Publications
Publication Date
11-8-2021
Journal
The American Journal of Clinical Nutrition
DOI
10.1093/ajcn/nqab260
PMID
34477824
PMCID
PMC8574623
PubMedCentral® Posted Date
9-3-2021
PubMedCentral® Full Text Version
Post-print
Published Open-Access
yes
Keywords
Adipose Tissue, Adolescent, Adult, Aged, Aged, 80 and over, Body Composition, Child, Child, Preschool, Cross-Sectional Studies, Energy Metabolism, Exercise, Female, Humans, Male, Middle Aged, Young Adult, physical activity level, age, energy expenditure, body composition, doubly labeled water
Abstract
BACKGROUND: Physical activity may be a way to increase and maintain fat-free mass (FFM) in later life, similar to the prevention of fractures by increasing peak bone mass.
OBJECTIVES: A study is presented of the association between FFM and physical activity in relation to age.
METHODS: In a cross-sectional study, FFM was analyzed in relation to physical activity in a large participant group as compiled in the International Atomic Energy Agency Doubly Labeled Water database. The database included 2000 participants, age 3-96 y, with measurements of total energy expenditure (TEE) and resting energy expenditure (REE) to allow calculation of physical activity level (PAL = TEE/REE), and calculation of FFM from isotope dilution.
RESULTS: PAL was a main determinant of body composition at all ages. Models with age, fat mass (FM), and PAL explained 76% and 85% of the variation in FFM in females and males < 18 y old, and 32% and 47% of the variation in FFM in females and males ≥ 18 y old, respectively. In participants < 18 y old, mean FM-adjusted FFM was 1.7 kg (95% CI: 0.1, 3.2 kg) and 3.4 kg (95% CI: 1.0, 5.6 kg) higher in a very active participant with PAL = 2.0 than in a sedentary participant with PAL = 1.5, for females and males, respectively. At age 18 y, height and FM-adjusted FFM was 3.6 kg (95% CI: 2.8, 4.4 kg) and 4.4 kg (95% CI: 3.2, 5.7 kg) higher, and at age 80 y 0.7 kg (95% CI: -0.2, 1.7 kg) and 1.0 kg (95% CI: -0.1, 2.1 kg) higher, in a participant with PAL = 2.0 than in a participant with PAL = 1.5, for females and males, respectively.
CONCLUSIONS: If these associations are causal, they suggest physical activity is a major determinant of body composition as reflected in peak FFM, and that a physically active lifestyle can only partly protect against loss of FFM in aging adults.
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