Influence of physical activity on hydration state in children with obesity before and after a weight loss program.

: Evaluate the effect of a 1-year standardized residential slimming program on exercise-induced dehydration in children with obesity. : At the start () and end () of the program, urine samples, weight, blood pressure and pulse were collected before () and after a Cooper test (). Urinary samples were analyzed for volume, Na (U), Cl, K (U), urea, creatinine (U), protein and osmolality (U). : All 66 children (15 ± 1 years) starting the program were included after informed consent (28 stopped prematurely). The Cooper test induced a significant weight loss at each test moment ( < 0.01). The resting U/(U + U) % increased significantly from 40 (±11) at to 50% (±11) at . Only in normal weight patients, exercise induced a significant increase in U/(U + U) % (: 49 ± 11; : 56 ± 12) ( < 0.01) as well as an increase in U/U mmol/mg (: 0.12 ± 0.07; : 0.1 ± 0.05) ( < 0.05). : The significant weight loss after exercise indicated significant dehydration. In patients with obesity, no aldosterone effect measured by U/(U + U)% was observed in contrast to the normal body mass index patients after the program.