The MicroKid project will acts first as a case-control study (Study I) in order to identify the hepatic steatosis and intestinal and salivary microbiota in children grouped as non-overweight, obese-non-hepatic steatosis, and obese-hepatic steatosis. Then, an intervention study (Study II) will be developed for those children with obesity (i.e., obese-non-hepatic steatosis, and obese-hepatic steatosis groups).~Methodology: A total of 60 children, 8-12 years-old, will be assigned to control (non-overweight children, N= 20), obese-non-hepatic steatosis (children with obesity, but without hepatic steatosis, N=20), and obese-hepatic steatosis (children with obesity and hepatic steatosis, N= 20) groups (Study I: case-control study). The obesity and obesity + hepatic steatosis groups will attend to a 12-weeks healthy lifestyle education program (2 days/month) and home-based exercise program (minimum 3 days/week) (Study II: intervention study).~The combined intervention program for the Study II will include: i) healthy lifestyle education program focused on dietary and lifestyle guidelines for both children and parents (2 days/month, 60 min), and ii) exercise program based on high-intensity interval training which combines aerobic and resistance training (at least 3 days/week, from 38 to 44 min).~Measurements: In the Study I (i.e., case-control study), all participants will be evaluated at baseline. For the Study II (i.e., intervention study), only those participants that belongs to obese-non-hepatic steatosis and obese-hepatic steatosis groups, will be additionally evaluated after the intervention program (12-week). The following outcomes will be measured: hepatic fat fraction and abdominal adiposity (magnetic resonance imaging), intestinal and salivary microbiota, body composition (bioimpedance), cardiometabolic risk factors, liver enzymes, physical fitness (field-fitness tests), physical activity (accelerometry), sleep (accelerometry), dietary habits (24h recalls, and food frequency questionnaires), and pubertal development and sociodemographic characteristics will be measured.
The objectives of the present study are: 1) to identify the intestinal and salivary microbiota associated with the presence and severity of hepatic steatosis in children (Study I: case-control study), and 2) to develop a personalized 12-week intervention program based on diet and exercise to examine its effects on the diversity and composition of the microbiota in children with hepatic steatosis (Study II: intervention study)