[Changes of kidney function in obese subjects during absolute fasting (author's transl)]

In 28 obese subjects the influence of a 15-days fasting period on the kidney function was investigated by continuous measurement of the clearances for creatinine, urea and uric acid. In the course of fasting time the serum concentrations of creatinine in comparison to the initial value significantly increased, the creatinine clearance maximally decreased about 40%. The serum concentrations of urea were found lower, whilst the clearance of urea increased. Moreover a distinct increase of the serum levels in connection with a significant decrease of the uric acid clearance was to be observed. Under conditions of strict fasting changes of the kidney function are evident, whose intra- and extrarenal reasons are discussed.