Effect of fasting on monosodium glutamate-obese rats.

The effect of fasting was studied in lean and monosodium glutamate (MSG)-obese rats. Daily urinary urea excretion and body weight loss were studied before and during 21 days of fasting. MSG-obese rats showed reduced weight loss, higher total liver lipid content, and lower urea excretion during fasting, thus suggesting a higher capacity to spare body protein in comparison to controls. A significant decrease in retroperitoneal fat pad content was observed in both groups after 6 days of fasting (83% in the controls vs 35% in MSG-obese rats). These data suggest that the larger lipid stores of MSG-obese rats can explain their greater mean survival time after fasting.