The Effect of a Multidisciplinary Weight Loss Program on Renal Circadian Rhythm in Obese Adolescents.

Adolescent obesity is a serious health problem associated with many comorbidities. Obesity-related alterations in circadian rhythm have been described for nocturnal blood pressure and for metabolic functions. We believe renal circadian rhythm is also disrupted in obesity, though this has not yet been investigated. This study aimed to examine renal circadian rhythm in obese adolescents before and after weight loss. In 34 obese adolescents (median age 15.7 years) participating in a residential weight loss program, renal function profiles and blood samples were collected at baseline, after 7 months, and again after 12 months of therapy. The program consisted of dietary restriction, increased physical activity, and psychological support. The program led to a median weight loss of 24 kg and a reduction in blood pressure. Initially, lower diurnal free water clearance (− 1.08 (− 1.40–− 0.79) mL/min) was noticed compared with nocturnal values (0.75 (− 0.89–− 0.64) mL/min). After weight loss, normalization of this inverse rhythm was observed (day − 1.24 (− 1.44–1.05) mL/min and night − 0.98 (− 1.09–− 0.83) mL/min). A clear circadian rhythm in diuresis rate and in renal clearance of creatinine, solutes, sodium, and potassium was seen at all time points. Furthermore, we observed a significant increase in sodium clearance. Before weight loss, daytime sodium clearance was 0.72 mL/min (0.59–0.77) and nighttime clearance was 0.46 mL/min (0.41–0.51). After weight loss, daytime clearance increased to 0.99 mL/min (0.85–1.17) and nighttime clearance increased to 0.78 mL/min (0.64–0.93). Conclusion: In obese adolescents, lower diurnal free water clearance was observed compared with nocturnal values. Weight loss led to a normalization of this inverse rhythm, suggesting a recovery of the anti-diuretic hormone activity. Both before and after weight loss, clear circadian rhythm of diuresis rate and renal clearance of creatinine, solutes, sodium, and potassium was observed.