Eccentric exercise results in muscle damage, transient insulin resistance and an increased insulin response to glucose among healthy young individuals. However, the bioenergetic response to eccentric exercise among healthy older individuals is unknown. Substrate metabolism was examined using hyperglycemic clamps (180 min, 10 mM) in 8 older (age, 66 ± 2 years; BMI, 25.5 ± 1.2 kg^.m^-2) and 9 younger (age, 23 ± 1 years; BMI, 23.6 ± 1.7 kg^.m^-2) sedentary men with normal oral glucose tolerance (OGTT), under control conditions and 48 h after eccentric exercise. Indirect calorimetry was performed at basal and 180 min of hyperglycemia to evaluate rates of carbohydrate and lipid oxidation (C_ox and L_ox, respectively). Eccentric exercise caused muscle soreness and increased plasma creatine kinase in both groups (P<0.02). Although a similar level of hyperglycemia was maintained in both groups, glucose infusion rates were lower (P<0.001) in older versus younger subjects, regardless of trial. Hyperglycemia stimulated an increase in C_ox and a decrease in L_ox during both trials in the younger group (P<0.03), but only under control conditions among older subjects (P<0.007). In order to evaluate the effects of eccentric exercise, oxidation rates during hyperglycemia were compared between control and exercise trials. C_ox was unchanged after eccentric exercise in younger (4.00 ± 0.30 vs. 3.54 ± 0.44 mg^.kgFFM^-1.min^-1; +13%, P=0.11; exercise vs. control), but suppressed by 20% among older men (3.37 ± 0.37 vs. 4.21 ± 0.23 mg^.kgFFM^-1.min^-1; P<0.04). Moreover, L_ox was diminished by 38% in younger subjects (0.47 ± 0.09 vs. 0.76 ± 0.10 mg^.kgFFM^-1.min^-1; P<0.03), but augmented by 89% in the older group (0.68 ± 0.11 vs. 0.36 ± 0.08 mg^.kgFFM^-1.min^-1; P<0.04). Respiratory exchange ratio (RER) increased in younger (0.93 ± 0.01 vs. 0.89 ± 0.02; P<0.03), and decreased in older subjects (0.89 ± 0.02 vs. 0.94 ± 0.01; P<0.03). In addition, hyperglycemia-stimulated C_ox, L_ox and RER responses to eccentric exercise were related to abdominal adiposity (r = -0.57, P<0.04, r = 0.66, P<0.02 and r = -0.60, P<0.02, respectively). Despite a normal OGTT and the absence of obesity per se, older men show aberrations in substrate metabolism after exercise-induced muscle damage. Thus, aging and modest increases in abdominal adiposity diminishes the metabolic response to hyperglycemia after a single bout of eccentric exercise.