Solomon, Thomas4; Haus, Jacob M3; Cook, Marc A3; Flask, Chris A3; Kirwan, John P3
1 Section of Cellular and Metabolic Research, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, Københavns Universitet2 Graduate School of Health and Medical Sciences, Faculty of Health and Medical Sciences, Københavns Universitet3 unknown4 Graduate School of Health and Medical Sciences, Faculty of Health and Medical Sciences, Københavns Universitet
Objective: To determine the influence of dietary glycemic index on exercise training-induced adaptations in substrate oxidation in obesity. Design and Methods: Twenty older, obese individuals undertook 3 months of fully supervised aerobic exercise and were randomized to low- (LoGIX) or high-glycemic (HiGIX) diets. Changes in indirect calorimetry (VO2 ; VCO2 ) were assessed at rest, during a hyperinsulinemic-euglycemic clamp, and during submaximal exercise (walking: 65% VO2 max, 200 kcal energy expenditure). Intramyocellular lipid (IMCL) was measured by (1) H-magnetic resonance spectroscopy. Results: Weight loss (-8.6 ± 1.1%) and improvements (P <0.05) in VO2 max, glycemic control, fasting lipemia, and metabolic flexibility were similar for both LoGIX and HiGIX groups. During submaximal exercise, energy expenditure was higher following the intervention (P <0.01) in both groups. Respiratory exchange ratio during exercise was unchanged in the LoGIX group but increased in the HiGIX group (P <0.05). However, fat oxidation during exercise expressed in relation to changes in body weight was increased in the LoGIX group (+10.6 ± 3.6%; P <0.05). Fasting IMCL was unchanged, however, extramyocellular lipid was reduced (P <0.05) after LoGIX. Conclusions: A LoGIX/exercise weight-loss intervention increased fat utilization during exercise independent of changes in energy expenditure. This highlights the potential therapeutic value of low-glycemic foods for reversing metabolic defects in obesity.