Postprandial skeletal muscle metabolism following a high fat diet in sedentary and endurance trained males.

Our objective was to determine the influence of a high-fat diet (HFD) on fasting and postprandial skeletal muscle substrate metabolism in endurance trained (ET) compared with sedentary (SED) humans. SED (n=17) and ET (n=7) males were control-fed a 10-day moderate-fat diet followed by a 5-day isocaloric HFD (55% fat, 30% carbohydrate). Skeletal muscle biopsies were taken in the fasted condition and 4 hours after a high-fat meal (820 kcals; 63% fat, 25% carbohydrate). Palmitate-induced suppression of pyruvate oxidation, an indication of substrate preference, and oxidation of fat and glucose were measured in homogenized skeletal muscle in fasted and fed states. Postprandial responses were calculated as percent changes from fasting to fed states. Postprandial suppression of pyruvate oxidation was maintained after the HFD in ET, but not SED skeletal muscle, suggesting greater adaptability to dietary intake changes in the former. Fasting total fat oxidation increased due to the HFD in ET skeletal muscle (P=0.006), which was driven by incomplete fat oxidation (P=0.008). Fasting fat oxidation remained unchanged in skeletal muscle of SED individuals. Yet, postprandial fat oxidation was similar between groups. Fasting glucose oxidation was elevated after the HFD in ET (P=0.036), but not SED, skeletal muscle. Postprandial glucose oxidation was reduced due to the HFD in SED (P=0.002), but not ET, skeletal muscle. These findings provide insight into differing substrate metabolism responses between SED and ET individuals and highlight the role the prevailing diet may play in modulating fasting and postprandial metabolic responses in skeletal muscle.