Effect of Sleep Extension on Body Weight and Learning in Children (More2Sleep)

More2Sleep is a randomized, controlled, parallel trial with two groups (sleep extension vs control) including 142 school-aged children (6-12 years) who have a BMI above average, defined as age- and sex-specific BMI Z-score above zero using WHO reference standards, and habitually sleep for ≤ 9 h/night. Data will be collected before and after a 3-month sleep extension intervention, and after a 6-month follow-up (at months 0, 3, and 9). The collection of data is mainly related to the main study. However, some optional examinations will be conducted on a first come, first serve basis, consisting of substudy-I (metabolic mechanisms, n=60) and substudy-II (learning mechanisms, n=142). The primary objective is to assess the effects of sleep extension by \~45 min/night, achieved by going to bed 60-90 min earlier, on adiposity and learning ability in school-aged children who have a BMI for age and sex above average, and sleep less than recommended for their age.