Postprandial triacylglycerol uptake in the legs is increased during exercise and post-exercise recovery

Six young, healthy male subjects were each studied in two experiments: (1) during resting conditions before and for 360 min after a meal (54% of energy as carbohydrate, 30% of energy as lipid, and 16% of energy as protein) comprising 25% of their total daily energy intake (M-->R); and (2) while exercising on a cycle ergometer for 60 min at 50% of the peak oxygen consumption commencing 60 min after the meal (M-->E) and then for another 240 min. Regional metabolism was measured by Fick's Principle in a leg and in the splanchnic tissue. The combination of food intake and exercise led to increased plasma triacylglycerol (TAG) uptake and clearance in the exercising legs immediately and for at least 4 h post-exercise, while food intake per se did not change leg plasma TAG uptake or clearance for up to 6 h. It is hypothesized that the effect of exercise on leg plasma TAG metabolism is a result of capillary recruitment leading to exposure of the plasma lipoprotein particles to a larger amount of active LPL. In spite of the increased TAG uptake in the exercising legs the arterial plasma TAG concentration had a tendency to increase faster during exercise after a meal than during rest, but it also decreased faster implying that the total lipaemic response was the same whether exercise was performed or not. The amount of lipid taken up in the legs was higher than could be accounted for by whole body lipid oxidation during post-exercise recovery, indicating accumulation of lipid in skeletal muscle in this period. Neither food intake alone nor the combination of food and exercise affected the splanchnic net balance of TAG. Finally, there is an additive effect of exercise and food intake on splanchnic net glucose balance.