DAILY VARIATIONS IN CATECHOLAMINE EXCRETION ARE NOT INFLUENCED BY VERY-LOW-CALORIE DIET IN OBESE WOMEN

The increase in metabolic efficiency during energy restriction seems to be an established phenomenon in obese patients. The sympathoadrenal system is involved in the control of energy expenditure and the catecholamine responses to stimuli vary during the day. We therefore studied the circadian pattern of urinary catecholamine excretion during 4-h collections for two consecutive days in a group of 20 obese female patients during and after a very low calorie diet (500 kcal/die). The diet period induced a significant weight loss in all the patients studied (99.1+/-3.7 vs 92.5+/-4.1 Kg; p<0.01). The mean daily excretion of epinephrine did not change after 24 days of diet restriction when compared with the value obtained at the 4th day (12.0+/-2.5 vs 10.3+/-2.2 nmol/4 h respectively; p=NS) while a slight decrease was observed in the mean daily excretion of norepinephrine (52.5+/-8.7 vs 66.6+/-9.3 nmol/4 h respectively; p=NS). A circadian rhythm was detected for epinephrine and norepinephrine excretion both during and after very low calorie diet. No significant changes were found in the chronobiological characteristics of epinephrine and norepinephrine with the peak of excretion in the afternoon both during (epinephrine: 16:30 h; norepinephrine: 16:45 h) and after the diet (epinephrine: 17:35 h; norepinephrine: 18:00 h). It seems doubtful that alterations in the chronobiological pattern of catecholamines play a role in the metabolic adaptation occurring during very low calorie diet in obese females.