Evaluation of hydration status of obese children

Background: Due to significant increase in childhood obesity, the studies focusing on the prevention of obesity become more of an issue. Although adequate hydration is recommended for healthy nutrition, the link between less water consumption and obesity is not exactly known. It was demonstrated that less hydrated adults had a higher body mass index (BMI). Data in children are rather limited. Our aim in this study was to compare the hydration status of obese children and teens with their normal weight peers. Subjects and Methods: Children aged between 7 and 18 years who admitted to the pediatric endocrinology outpatient clinic and had an BMI over 2 standard deviation score (SDS) with exogenous obesity were included in the study group (Group 1, n=31), healthy volunteers with a normal weight were included in the control group (Group 2, n=30). The anthropometric measurements of all subjects were performed and body composition analysis was applied using bioelectrical impedance analysis method (TANITA BC 418). Urine density was tested at the same time of the day after ad libitum water consumption and lunch. The fluid intake diary was recorded over two consecutive days using two different methods. Total fluid intake was compared with European Food Safety Authority (EFSA) recommendations. The intake of water and sweetened beverages were compared between groups. Results: Mean age was 11.71 ± 3.3 years in Group 1 (16 females, 15 males) and 11.24 ± 2.5 years in Group 2 (16 females, 14 males); there was no differences regarding age and gender between groups (p>0.005 for both). The median BMI-SDS was 2.57 (0.52) kg/m2 in Group 1 and 0.01 (1.48) kg/m2 in Group 2 (p < 0.001). Body composition analysis showed that subjects in Group 1 had a higher percentage of body fat (p <0.001), and lower percentages of total body water and fat free mass (p=0.007 and <0.001 respectively). There was no difference regarding waist/hip ratio between groups (0.90 ±0.04 and 0.88 ±0.05, p=0.276). The fluid intake per body surface of Group 1 was found significantly less than Group 2 both in the first and in the second day (p<0.001). The urine density was found significantly higher in Group 1 (1020 (10) and 1015(10), p<0.001). While urine density correlated positively with BMI-SDS (r=0.508, p=<0.001), it was negatively correlated with total body water (r=-0.412, p=0.001) and fluid intake per body surface (first day: r=-0.477, p<0.001, second day: r=-0.519, p<0.001). While 55% of subjects (n=17) in Group 1 satisfied the recommended daily fluid intake, this was 80% (n=24) in Group 2 (p=0.036). There was consumption of sugar sweetened beverages in 22 subjects in Group 1 (71%) and in 6 subjects in Group 2 (20%). The amount of sugar sweetened beverages was higher in Group 1 (median 200 ml vs 0 ml, p<0.001). Conclusions: We found that obese children had less fluid intake, lower total body water percentages and higher urine density. The results of this cross-sectional preliminary study showed that obese children were less hydrated than normal weighted children. Further large scaled studies are needed to demonstrate the relation between correction of hydration status and weight control. Keywords: Obesity, fluid intake, Hydration, Urine density, Body composition analysis