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Multicenter Study
. 2020 Jun 18;75(7):1362-1368.
doi: 10.1093/gerona/glaa064.

The Importance of Muscle Versus Fat Mass in Sarcopenic Obesity: A Re-evaluation Using D3-Creatine Muscle Mass Versus DXA Lean Mass Measurements

Eric S Orwoll  1 , Katherine E Peters  2 , Marc Hellerstein  3 , Steven R Cummings  4   5 , William J Evans  3   6 , Peggy M Cawthon  4   7
Affiliations
Multicenter Study

The Importance of Muscle Versus Fat Mass in Sarcopenic Obesity: A Re-evaluation Using D3-Creatine Muscle Mass Versus DXA Lean Mass Measurements

Eric S Orwoll et al. J Gerontol A Biol Sci Med Sci. .

Abstract

Background: The combination of sarcopenia and obesity has been associated with physical impairment in older people. However, previous research has relied on assessments of lean mass as a surrogate for muscle mass. We postulate that inaccurate measures of muscle mass may have obscured the role of obesity in sarcopenia and related outcomes. Our aim was to clarify the interactions of muscle and fat with physical performance and adverse outcomes using an accurate measure of muscle mass.

Methods: In a longitudinal study of >1,300 older men (mean age 84 years), we compared a direct measurement of muscle mass (D3 creatine dilution; D3Cr) with an approximation of muscle mass (appendicular lean mass [ALM] by dual-energy x-ray absorptiometry [DXA]) and their associations with measures of physical performance (gait speed, chair stand time) and adverse outcomes (incident injurious falls and mobility problems). We measured percent fat mass by DXA.

Results: Low D3Cr muscle mass was strongly associated with decreased performance and increased risk of adverse outcomes. Increased fat mass had little association after accounting for D3Cr muscle mass. In contrast, DXA ALM was minimally associated with performance or adverse outcomes, and fatness remained associated with both outcomes after accounting for DXA ALM.

Conclusions: When an accurate assessment of muscle mass (rather than lean mass) is used, reduced muscle mass is highly associated with important outcomes and the negative effects of adiposity are minimal, suggesting that obesity has little relevance for the understanding of important adverse health outcomes of sarcopenia in older men.

Keywords: Aging; Disability; Sarcopenia.

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Figures

Figure 1.
Figure 1.
Comparison of components of body composition, each as a percent of body weight, in 1,376 older men. In combination, the three-compartment DXA measures of bone mineral, fat and total lean equal 100%. Superimposed are the measures of D3Cr muscle and DXA ALM. The men are ranked with those with highest D3Cr on the left and lowest on the right. ALM = appendicular lean mass; DXA = dual-energy x-ray absorptiometry.
Figure 2.
Figure 2.
The associations between physical performance measures and D3Cr muscle mass or ALM. All models are adjusted for age. ALM = appendicular lean mass. (A) Mean walking speed by quartiles of D3Cr muscle mass/wgt and %fat. Interaction p-value derived from a model with continuous fat, D3Cr muscle mass/wgt and an interaction term. Fat quartile cut points: Q1<23.84, Q2 23.84–<27.82, Q3 27.82–<31.86, Q4≥ 31.86. D3Cr muscle mass/wgt Quartile Cut points: Q1<0.27, Q2 0.27–<0.30, Q3 0.30–<0.34, Q4≥0.34. (B) Mean walking speed by quartiles of ALM/ht2 and %fat. Interaction p-value derived from a model with continuous fat, ALM/ht2, and an interaction term. Fat quartile cut points: Q1<23.84, Q2 23.84–<27.82, Q3 27.82–<31.86, Q4≥31.86. ALM/ht2 Quartile cut points: Q1<6.93, Q2 6.93–<7.49, Q3 7.49–<8.11, Q4≥8.11. (C) Mean number of chair stands per 10 s by quartiles of D3Cr muscle mass/wgt and %fat. Interaction p-value derived from a model with continuous fat, D3Cr muscle mass/wgt and an interaction term. Fat quartile cut points: Q1<23.84, Q2 23.84–<27.82, Q3 27.82–<31.86, Q4≥ 31.86. D3Cr muscle mass/wgt quartile cut points: Q1<0.27, Q2 0.27–<0.30, Q3 0.30–<0.34, Q4≥0.34. (D) Mean number of chair stands per 10 seconds by quartiles of ALM/ht2 and %fat. Interaction p-value derived from a model with continuous fat, ALM/ht2 and an interaction term. Fat quartile cut points: Q1<23.84, Q2 23.84–<27.82, Q3 27.82–<31.86, Q4≥31.86. ALM/ht2 quartile cut points: Q1<6.93, Q2 6.93–<7.49, Q3 7.49–<8.11, Q4≥8.11. ALM = appendicular lean mass; wgt = weight.
Figure 3.
Figure 3.
The likelihood of mobility limitation and injurious falls by fat categories and D3Cr muscle mass or ALM. Men are stratified into higher and lower percent fat (Quartile 4 vs Quartiles 1–3) and either higher or lower D3Cr muscle mass/wgt or high or low ALM/ht2 (Quartile 1 vs Quartiles 2–4). * Significant at p < .05 against reference group. (A) Likelihood of prevalent mobility limitation by muscle and fat groups using quartiles of D3Cr muscle mass/wgt and %fat. Interaction p-value derived from a model with continuous fat, D3Cr muscle mass/wgt and an interaction term. Fat quartile cut points: High Q4≥ 31.86, Low Q1–3 <31.86. D3Cr muscle mass/wgt quartile cut points: High Q2–4≥0.27, Low Q1<0.27. (B) Likelihood of prevalent mobility limitation by lean and fat groups using quartiles of ALM/ht2 and %fat. Interaction p-value derived from a model with continuous fat, ALM/ht2 and an interaction term. Fat quartile cut points: High Q4≥ 31.86, Low Q1–3 <31.86. ALM/ht2 quartile cut points: High Q2–4≥6.93, Low Q1<6.93. (C) Likelihood of incident mobility limitation by muscle and fat groups using quartiles of D3Cr muscle mass/wgt and %fat. Interaction p-value derived from a model with continuous fat, D3Cr muscle mass/wgt and an interaction term. Fat quartile cut points: High Q4≥31.00, Low Q1–3<31.00. D3Cr muscle mass/wgt quartile cut points: High Q2–4≥0.28, Low Q1<0.28. (D) Likelihood of incident mobility limitation by lean and fat groups using quartiles of ALM/ht2 and %fat. Interaction p-value derived from a model with continuous fat, ALM/ht2 and an interaction term. Fat quartile cut points: High Q4≥31.00, Low Q1–3<31.00. ALM/ht2 quartile cut points: High Q2–4 ≥6.93, Low Q1<6.93. (E) Likelihood of incident injurious falls by muscle and fat groups using quartiles of D3Cr/wgt and %fat. Interaction p-value derived from a model with continuous fat, D3Cr muscle mass/wgt and an interaction term. Fat quartile cut points: High Q4≥ 31.86, Low Q1–3 <31.86. D3Cr muscle mass/wgt quartile cut points: High Q2–4≥0.27, Low Q1<0.27. (F) Likelihood of incident injurious falls by lean and fat groups using quartiles of ALM/ht2 and %fat. Interaction p-value derived from a model with continuous fat, ALM/ht2 and an interaction term. Fat quartile cut points: High Q4≥ 31.86, Low Q1–3 <31.86. ALM/ht2 quartile cut points: High Q2–4≥6.93, Low Q1<6.93. ALM = appendicular lean mass; wgt = weight.
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