Journal Article

Muscle mass, BMI, and mortality among adults in the United States: A population-based cohort study

Hall, Charles B., Sharma, Deep, Hawkins, Meredith, Abramowitz, Matthew K., Androga, Lagu, Amodu, Afolarin

2018

Overview

The level of body-mass index (BMI) associated with the lowest risk of death remains unclear. Although differences in muscle mass limit the utility of BMI as a measure of adiposity, no study has directly examined the effect of muscle mass on the BMI-mortality relationship. Body composition was measured by dual-energy x-ray absorptiometry in 11,687 participants of the National Health and Nutrition Examination Survey 1999-2004. Low muscle mass was defined using sex-specific thresholds of the appendicular skeletal muscle mass index (ASMI). Proportional hazards models were created to model associations with all-cause mortality. At any level of BMI ≥22, participants with low muscle mass had higher body fat percentage (%TBF), an increased likelihood of diabetes, and higher adjusted mortality than other participants. Increases in %TBF manifested as 30-40% smaller changes in BMI than were observed in participants with preserved muscle mass. Excluding participants with low muscle mass or adjustment for ASMI attenuated the risk associated with low BMI, magnified the risk associated with high BMI, and shifted downward the level of BMI associated with the lowest risk of death. Higher ASMI was independently associated with lower mortality. Effects were similar in never-smokers and ever-smokers. Additional adjustment for waist circumference eliminated the risk associated with higher BMI. Results were unchanged after excluding unintentional weight loss, chronic illness, early mortality, and participants performing muscle-strengthening exercises or recommended levels of physical activity. Muscle mass mediates associations of BMI with adiposity and mortality and is inversely associated with the risk of death. After accounting for muscle mass, the BMI associated with the greatest survival shifts downward toward the normal range. These results provide a concrete explanation for the obesity paradox.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Absorptiometry, Photon / Adipose tissue / Adipose Tissue - physiology / Adiposity / Adult / Adults / Biology and Life Sciences / Body Composition / Body composition (biology) / Body fat / Body mass / Body Mass Index / Body weight loss / Cardiovascular disease / Chronic illnesses / Cohort analysis / Cohort Studies / Death / Diabetes / Diabetes mellitus / Dual energy X-ray absorptiometry / Energy measurement / Epidemiology / Exercise / Female / Forecasts and trends / Hazards / Health aspects / Heart failure / Humans / Male / Measurement methods / Medicine / Medicine and Health Sciences / Middle Aged / Mortality / Muscles / Muscles - physiology / Nutrition / Nutrition Surveys / Obesity / Physical activity / Population / Population studies / Population-based studies / Probability / Quality of life / Risk / Risk Factors / Sarcopenia / Skeletal muscle / Smoking / Statistical models / Studies / United States / Waist Circumference / Weight control / Womens health