Diurnal changes in plasma lipoproteins of free-living healthy men consuming a standard diet

Although it is well established that plasma lipoproteins are involved in atherogenesis, most patients with coronary heart disease have normal or nearly normal fasting plasma lipid and lipoprotein levels. As most of the human life is spent in the fed state we elected to investigate the changes occurring in plasma lipids and lipoproteins during normal daily activities. We studied 12 healthy, normolipidemic and non-obese subjects on a standard diet divided into three meals and three snacks. This method was found to be accurate and reproducible in four subjects who underwent repeated studies. The major diurnal changes were observed in plasma triglyceride level and in the composition of plasma lipoproteins. The degree and pattern of these changes differed among subjects but was specific and constant for each individual. The extent of these diurnal changes, which correlated positively with fasting plasma triglyceride and inversely with plasma HDL₂ levels, may play an important role in the pathogenesis of atherosclerosis.