Background and study design: Weight reduction can be obtained by decreased appetite or increased metabolism. However, acute weight loss can also be obtained by loss of fluids - for example by increased urinary loss of fluid and salts, so called elctrolytes. Preliminary results from a laboratory lesson for the Master of Science in Medicine program at University of Gothenburg suggest that carrying a 10 kg weight vest could increase urinary excretion of Na+, K+ and Cl-. The purpose of this study is to investigate this further in a more controlled research setting. If confirmed, the results could potentially contribute to the development of potent diuretics or obesity medicines.