Long-term effects of a high-carbohydrate diet and exercise on insulin action in older subjects with impaired glucose tolerance.
Carbohydrate metabolism was assessed in 20 glucose-intolerant subjects before and after 12 wk on a high-carbohydrate diet (HC) or the diet combined with exercise training (HC-EX). The diet provided 60% of energy as carbohydrate and 20% as fat. Neither treatment altered fasting glucose or insulin concentrations or their response to a meal. During a glucose clamp (216 pmol insulin/L) glucose disposal increased from 13.2 +/- 0.83 to 14.6 +/- 0.83 mumol.kg fat-free mass-1.min-1 (P < 0.05) in both groups. During more pronounced hyperinsulinemia (654 pmol/L) glucose disposal did not change significantly (49.9 +/- 3.8 to 50.7 +/- 3.8 mumol.kg fat-free mass-1.min-1). Muscle glycogen increased in the HC-EX group (78.5 +/- 8.1 to 161.1 +/- 15.7 mmol glucose/kg muscle), with no changes in the HC group. These results do not support the recommendation to increase the dietary carbohydrate content for improving postprandial glucose metabolism or insulin action in glucose-intolerant adults unless combined with exercise training, which promotes muscle glycogen storage.
Hughes
V A
VA
US Department of Agriculture Jean Mayer Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111, USA.
Fiatarone
M A
MA
Fielding
R A
RA
Ferrara
C M
CM
Elahi
D
D
Evans
W J
WJ
D000368:Aged; D000375:Aging / Q000502:physiology*; D001786:Blood Glucose / Q000032:analysis; D001823:Body Composition; D004040:Dietary Carbohydrates / Q000378:metabolism / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005260:Female; D015309:Glucose Clamp Technique; D005951:Glucose Tolerance Test; D006003:Glycogen / Q000032:analysis; D006801:Humans; D006946:Hyperinsulinism / Q000097:blood; D007328:Insulin / Q000097:blood / Q000502:physiology*; D007333:Insulin Resistance / Q000235:genetics / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000737:chemistry; D013997:Time Factors
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D007328:Insulin; D006003:Glycogen