Lactic acid… The byproduct of anaerobic metabolism works as anti- lipolytic during exercise.
Using fat as source of energy during exercise is crucial. This make sure that muscle is able to work even though glucose is already depleted. And one of the most important process to provide fat during this exercise is lipolysis. This process happeneds both in muscle cells and adipocytes. Four hormones regulate lipolysis during exercise, those are catecholamine, adrenaline, noradrenaline and insulin.
From those hormones, insulin is the hormone that works to inhibit lipolysis. However, recent finding showed that insulin is not the only hormone that block fatty acid production during exercise. Lactate or lactic acid, which is released into plasma also take part in this lipid metabolism processes. Plasma lactate has been shown associated with low level of FA during exercise. Some studies have revealed why this phenomena happend.
Lactate appears to reduce FA production at adipose tissue. If glucose and muscle glycogen are not used, lactate will bring signal to body to lower its performance with manifestation as fatigue. Lactate, because of its chemical property, decreases pH of the blood leading to reduction of many enzymatic pathway. Scienists used dog as an example. By giving infusion of lactate to the dog, Issekutz shown that the release of FA during exercise could be inhibited. This study has also been done in human.
Ranallo RF, Rhodes EC. Lipid metabolism during exercise. Sports Med, 1998, 26: 29-42.