title: Sarcopenia exacerbates obesity-associated insulin resistance and dysglycemia: findings from the National Health and Nutrition Examination Survey III.
abstract: BACKGROUND
  Sarcopenia often co-exists with obesity, and may have additive effects on insulin resistance. Sarcopenic obese individuals could be at increased risk for type 2 diabetes. We performed a study to determine whether sarcopenia is associated with impairment in insulin sensitivity and glucose homeostasis in obese and non-obese individuals.
  
  
  METHODS
  We performed a cross-sectional analysis of National Health and Nutrition Examination Survey III data utilizing subjects of 20 years or older, non-pregnant (N = 14,528). Sarcopenia was identified from bioelectrical impedance measurement of muscle mass. Obesity was identified from body mass index. Outcomes were homeostasis model assessment of insulin resistance (HOMA IR), glycosylated hemoglobin level (HbA1C), and prevalence of pre-diabetes (6.0≤ HbA1C<6.5 and not on medication) and type 2 diabetes. Covariates in multiple regression were age, educational level, ethnicity and sex.
  
  
  RESULTS
  Sarcopenia was associated with insulin resistance in non-obese (HOMA IR ratio 1.39, 95% confidence interval (CI) 1.26 to 1.52) and obese individuals (HOMA-IR ratio 1.16, 95% CI 1.12 to 1.18). Sarcopenia was associated with dysglycemia in obese individuals (HbA1C ratio 1.021, 95% CI 1.011 to 1.043) but not in non-obese individuals. Associations were stronger in those under 60 years of age. We acknowledge that the cross-sectional study design limits our ability to draw causal inferences.
  
  
  CONCLUSIONS
  Sarcopenia, independent of obesity, is associated with adverse glucose metabolism, and the association is strongest in individuals under 60 years of age, which suggests that low muscle mass may be an early predictor of diabetes susceptibility. Given the increasing prevalence of obesity, further research is urgently needed to develop interventions to prevent sarcopenic obesity and its metabolic consequences.
authors.affiliation: Division of Gerontology, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA. psrikanthan@mednet.ucla.edu
authors.forename: Preethi
authors.initials: P
authors.lastname: Srikanthan
authors.forename: Andrea L
authors.initials: AL
authors.lastname: Hevener
authors.forename: Arun S
authors.initials: AS
authors.lastname: Karlamangla
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D015897:Comorbidity; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology; D004522:Educational Status; D005260:Female; D018149:Glucose Intolerance / Q000453:epidemiology*; D006801:Humans; D007333:Insulin Resistance; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009749:Nutrition Surveys; D009765:Obesity / Q000453:epidemiology*; D011236:Prediabetic State / Q000453:epidemiology; D015995:Prevalence; D055948:Sarcopenia / Q000453:epidemiology*; D012737:Sex Factors; D014481:United States / Q000453:epidemiology