Intracellular electrolytes and hormonal parameters during weight reduction

The mechanisms of the blood pressure lowering effect of weight reduction have not yet been fully elucidated. In this study the intracellular electrolyte composition and hormonal parameters were monitored in 12 obese subjects during a 10-day diet with 800 kcal/day. A decrease in intracellular free Na⁺ (p < 0.05) and Mg²⁺ (p < 0.01) and in total intracellular K⁺ (p < 0.05) was observed. Furthermore, plasma aldosterone and renin activity (p < 0.05) increased, probably due to a moderate simultaneous salt restriction. There was also an increase in plasma PGI₂ concentration (p < 0.05). The observed decrease in intracellular free Na⁺ may be caused by salt restriction. The decrease in intracellular K⁺ and free Mg²⁺ may be induced by hormonal factors, e.g. an altered insulin secretion. Possible causes for the known hemodynamic effects of weight reduction are the diminution of intracellular Na⁺ and the increase in plasma PGI₂.