COMBINED INCREASES IN MUSCLE-STRENGTHENING ACTIVITY FREQUENCY AND PROTEIN INTAKE REVEAL GRADED RELATIONSHIP WITH FAT-FREE MASS PERCENTAGE IN U.S. ADULTS, NHANES (1999-2004)
J.M. Kurka, J. Vezina, D.D. Brown, J. Schumacher, R.W. Cullen, K.R. Laurson
J Frailty Aging 2015;4(1):26-33
Background: Age-related loss of muscle mass and related ailments are of concern due to associations with disabilities and morbidity as well as constituting a substantial healthcare burden. Muscle-strengthening activities and adequate protein ingestion are recommended for all-age adults in an effort to stave off age-related muscle atrophy. Muscle building abilities decline with age but most research focuses on muscle wasting in the elderly. Objectives: To examine the independent and combined associations of protein intake (g∙kg-1∙day-1) and muscle-strengthening frequency (times∙week-1, MSF) on fat-free mass percentage (FFM%). Design Setting and Participants: This cross-sectional analysis of a population-based sample with data from the non-institutionalized persons in the United States participating in the National Health and Nutrition Examination Survey (cycles 1999-2000, 2001-2002, 2003-2004) consisted of male (n=2,499) and female (n=2,373) participants 20-49 years of age for analyses. Measurements: MSF was determined by self-report and protein intake was calculated from a 24-hour recall. Differences in FFM% from bioelectrical impedance analysis was estimated using multiple linear regression models controlling for education, race-ethnicity, standing height, and total Caloric intake. Results: One unit increase in MSF or protein intake (β-coefficient, ±SE) was associated with significantly more FFM% in males (0.6±0.1%; 3.5±0.4%) and females (0.4±0.1%; 5.9±0.4%). Independent of protein intake, males and females with MSF=0 had mean ±SE FFM% of 74.4±0.4 and 60.7±0.3, respectively, while mean ±SE FFM% of males and females who met the recommendation of ≥2 times per week were 77.9±0.5 and 63.0±0.4. Independent of MSF, males and females with protein intakes below the recommended dietary allowance (RDA) of 0.8 g∙kg-1∙day-1 had mean ±SE FFM% of 74.0±0.6 and 58.2±0.6, respectively, while mean ±SE FFM% of those whose intakes exceeded the recommendation were 75.6±0.4 and 62.0±0.4. The subgroup with the highest mean ±SE FFM% (80.9 ±0.73) comprised males with MSF ≥2 times per week who also consumed >1.4 g∙kg-1∙day-1. Conclusion: The MSF-protein intake dose relationship with FFM% suggests that performing muscle-strengthening activities >2 times per week while consuming protein above the RDA may result in more fat-free mass and slow age-related losses of muscle mass.
J.M. Kurka ; J. Vezina ; D.D. Brown ; J. Schumacher ; R.W. Cullen ; K.R. Laurson (2015): Combined Increases in Muscle-strengthening Activity Frequency and Protein Intake Reveal Graded Relationship with Fat-free Mass Percentage in U.S. Adults, NHANES (1999-2004). The Journal of Frailty and Aging (JFA). http://dx.doi.org/10.14283/jfa.2015.37