title: Metabolic inflexibility during submaximal aerobic exercise is associated with glucose intolerance in obese older adults.
abstract: OBJECTIVE
  People with type 2 diabetes have reduced cardiorespiratory fitness and metabolic impairments that are linked to obesity and often occur prior to the development of type 2 diabetes. We hypothesized that obese, older adults with impaired glucose tolerance (IGT) have lower ability to shift from fat to carbohydrate oxidation when transitioning from rest to submaximal exercise than normal glucose tolerant (NGT) controls.
  
  
  METHODS
  Glucose tolerance, body composition, and substrate oxidation (measured by RER:respiratory exchange ratio) during submaximal exercise (50% and 60% VO₂max ) and insulin infusion (3-hour hyperinsulinemic-euglycemic clamp) were assessed in 23 sedentary, overweight-obese, older men and women.
  
  
  RESULTS
  Obese subjects with NGT (n = 13) and IGT (n = 10) had similar resting RER, but during submaximal exercise those with IGT had a lower RER and less transition to carbohydrate oxidation than the NGT group (P < 0.05). The IGT group also oxidized less carbohydrate during insulin infusion than NGT (P < 0.05). RER at each exercise intensity independently correlated with 120-minute postprandial glucose (r = -0.54 to -0.58, P < 0.05), but not with body composition, VO₂max , or RER during insulin infusion.
  
  
  CONCLUSIONS
  Obese, older adults have metabolic inflexibility during exercise that is associated with the degree of glucose intolerance independent of age and body composition.
authors: Baltimore Veterans Affairs Geriatric Research, Education and Clinical Center and Research and Development Service, Baltimore, Maryland, USA; Division of Gerontology and Geriatric Medicine, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors: Steven J
authors: SJ
authors: Prior
authors: Alice S
authors: AS
authors: Ryan
authors: Troy G
authors: TG
authors: Stevenson
authors: Andrew P
authors: AP
authors: Goldberg
mesh_terms: D000368:Aged; D000375:Aging; D001481:Basal Metabolism / Q000187:drug effects; D001823:Body Composition; D015992:Body Mass Index; D050260:Carbohydrate Metabolism / Q000187:drug effects; D015444:Exercise; D005260:Female; D018149:Glucose Intolerance / Q000150:complications / Q000378:metabolism*; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D007333:Insulin Resistance; D050356:Lipid Metabolism / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications*; D050177:Overweight / Q000150:complications; D010101:Oxygen Consumption / Q000187:drug effects; D057185:Sedentary Behavior
chemical_list: D007004:Hypoglycemic Agents; D007328:Insulin
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