Plasma-triglycerides and exercise: a delicate balance.

Alimentary lipemia was studied in 12 healthy young men with and without exercise. Three sets of experiments were performed. While continuous exercise of 90 min duration significantly reduced postprandial triglycerides by 26% (study I), this effect could not be observed when exercise was interrupted for 5 min after each 25 min (study II). Plasma free fatty acid concentrations, in the latter experiment, were significantly higher (by 311%) than during rest. When, in a third experiment continuous exercise was compared with intermittent physical activity, the latter condition significantly increased postprandial triglyceridemia, most probably due to precipitous rises of free fatty acids on each interruption of ergometry. It is concluded that in the third experiment the balance between triglyceride removal and triglyceride synthesis was shifted toward the latter. Whether exercise lowers, leaves unaltered, or raises plasma triglyceride levels may depend on subtle changes of experimental design.