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 are overweight or obese, and sleep less than recommended for their age. conditions: Sleep Duration conditions: Child Obesity conditions: Child Development conditions: Child Behavior studyType: INTERVENTIONAL phases: NA allocation: RANDOMIZED interventionModel: PARALLEL primaryPurpose: TREATMENT masking: NONE count: 300 type: ESTIMATED name: Sleep extension measure: BMI Z-score measure: Learning ability: skill learning measure: Learning ability: Explicit memory measure: Body fat percent measure: Total fat mass (FM) measure: Total lean mass (LM) measure: Bone mineral content (BMC) measure: Bone mineral density (BMD) measure: Dietary energy intake measure: Dietary protein, carbohydrate, fiber, and fat intakes measure: Subjective hunger measure: Physical activity (PA) time: total PA and MVPA measure: Resting metabolic rate (RMR) measure: Thermic effect of food (TEF) measure: Weight measure: Height measure: Total energy expenditure (TEE) measure: Fasting and postprandial glucose concentration measure: Fasting and postprandial insulin concentration measure: Fasting and postprandial total, HDL and LDL cholesterol concentrations measure: Fasting and postprandial triglyceride concentration measure: Fasting and postprandial C-reactive protein concentration measure: Fasting and postprandial tumor necrosis factor alpha concentration measure: Fasting and postprandial ghrelin concentration measure: Fasting and postprandial leptin concentration measure: Fasting and postprandial glucagon like peptide 1 concentration measure: Fasting and postprandial peptide YY concentration measure: Fasting and postprandial cholecystokinin concentration measure: Fasting and postprandial interleukin 6 concentration measure: Cognitive functions: processing speed measure: Cognitive functions: Sustained attention measure: Cognitive functions: Spatial working memory measure: Cognitive functions: Inhibitory control measure: Cognitive functions: Cognitive flexibility measure: School performance: mathematics performance measure: School performance: reading comprehension measure: Neurophysiological Measurement 1 - ERP Amplitude measure: Neurophysiological Measurement 2 - Cortical activity during skill learning measure: Neurophysiological Measurement 3 - Muscle activity during skill learning measure: Neurophysiological Measurement 4 - corticocortical functional connectivity measure: Neurophysiological Measurement 5 - corticomuscular connectivity measure: Health-related quality of life: child-reported measure: Health-related quality of life: parent-reported measure: Mental health: parent-reported measure: Parental Stress Scale: parent-reported measure: Perceived Stress Scale: child-reported measure: Demographics: income measure: Demographics: education measure: Wakefulness measure: Handedness measure: Fine Motor Control measure: Muscle strength measure: Brain myelination measure: Brain structural connectivity and microstructure measure: Brain functional connectivity measure: Vital signs: blood pressure measure: Vital signs: heart rate measure: Vital signs: temperature measure: Sleep quality: self-reported sleep duration measure: Sleep quality: self-reported latency measure: Sleep quality: self-reported awakenings measure: Sleep quality: self-reported tiredness/sleepiness measure: Sleep quality and architecture: Sleep stages measure: Sleep quality and architecture: sleep duration measure: Sleep quality and architecture: sleep latency measure: Sleep quality and architecture: awakenings measure: Sleep quality and architecture: arousals measure: Sleep: duration measure: Sleep: movements measure: Sleep: awakenings measure: Brain structure: cortical thickness measure: Brain structure: volume measure: Brain structure: Surface measure: Brain structure: volumes of subcortical grey matter structures sex: ALL minimumAge: 6 Years maximumAge: 9 Years stdAges: CHILD facility: University of Copenhagen city: Copenhagen zip: 1958 country: Denmark name: Faidon Magkos, PhD role: CONTACT phone: +45 35 33 36 71 email: fma@nexs.ku.dk name: Cecilie Rasmussen, MSc role: CONTACT phone: +45 35 33 58 27 email: chr@nexs.ku.dk name: Faidon Magkos, PhD role: PRINCIPAL_INVESTIGATOR name: Jesper Lundbye-Jensen, PhD role: SUB_INVESTIGATOR name: Poul Jennum, MD role: SUB_INVESTIGATOR lat: 55.67594 lon: 12.56553 facility: University of Copenhagen city: Copenhagen zip: 2200 country: Denmark name: Faidon Magkos, PhD role: CONTACT phone: +45 35 33 36 71 email: fma@nexs.ku.dk name: Jesper Lundbye-Jensen, PhD role: CONTACT phone: +45 35 32 73 30 email: jlundbye@nexs.ku.dk name: Faidon Magkos, PhD role: PRINCIPAL_INVESTIGATOR name: Jesper Lundbye-Jensen, PhD role: SUB_INVESTIGATOR name: Poul Jennum, MD role: SUB_INVESTIGATOR lat: 55.67594 lon: 12.56553 facility: Faidon Magkos city: Hvidovre zip: 2650 country: Denmark name: Faidon Magkos, PhD role: CONTACT phone: +45 35 33 36 71 email: fma@nexs.ku.dk name: Faidon Magkos, PhD role: PRINCIPAL_INVESTIGATOR name: Jesper Lundbye-Jensen, PhD role: SUB_INVESTIGATOR name: Kathrine Madsen, PhD role: SUB_INVESTIGATOR name: Hartwig Siebner, MD role: SUB_INVESTIGATOR name: Poul Jennum, MD role: SUB_INVESTIGATOR lat: 55.65719 lon: 12.47364 hasResults: False