Body Potassium Content in Obese Subjects and Potassium Depletion During Prolonged Fasting

Abstract

Serum potassium levels of the starving obese subjects studied decreased only slightly and did not necessarily mirror tissue depletion. Renal potassium loss was variable in different subjects. Losses were high during the first three weeks, decreasing gradually, but complete renal conservation could not be attained regardless of the length of the starvation period. During this initial phase of the starvation period, potassium could not be liberated from catabolized protein in quantities sufficient to prevent tissue depletion, but definite clinical symptoms of potassium deficiency did not develop. Urinary potassium to nitrogen ratios varied greatly. The highest ratios (4:1) were observed in patients who had not received potassium supplements; the lowest ratios, based on balance data, occurred in those patients who had had a preliminary adaptive period on a low calorie diet and were given potassium supplements during starvation. Total body K40cannot be used as a measure of body potassium in obese subjects unless a graduated correction factor based on the degree of obesity is employed. Applying this factor, most obese subjects are found to have increased body potassium.