Over the past decade, the relationship between obesity and sleep has become more salient. Obesity has been identified as an important risk factor for the obstructive sleep apnea syndrome (OSAS) [1-6]; therefore, this syndrome will be the main focus of this review. OSAS is a common disorder with prevalence estimates of 15-25% in adult men and 5-10% in adult women [6-11], and between 2-15% in children [2, 12, 13]. It is associated with intermittent hypoxemia, hypercapnia, arousals and sleep fragmentation. Symptoms include snoring, snorting, pauses in breathing, mouth breathing and daytime sleepiness. Children may also exhibit hyperactivity or daytime behavioral problems [14-16]. In adults, there is an association with increased morbidity and mortality, stroke, hypertension, atrial fibrillation, injuries, and cognitive impairment and Alzheimer’s disease [17-21]. Short- and long-term effects of untreated OSAS in pediatric patients include significant morbidity such growth failure [22], systemic [23-25] and pulmonary hypertension [26, 27], endothelial dysfunction [28, 29], and cognitive and behavioral deficits [16, 30-34]. Children who have both obesity and OSAS have increased cardiometabolic risk compared to children who are obese without OSAS. They also present with sleepiness, attention and executive dysfunction, mood concerns, and decreased quality of life [35-41]. There are little data regarding the long-term consequences of having both pediatric obesity and OSAS. One common risk factor for OSAS in adults is excess adiposity [4-6, 10, 11, 42]. An estimated 1% increase in BMI is associated with a 3% increase in the apnea hypopnea index (AHI) [4]. In children 2-5 years of age, the most common cause of OSAS is adenotonsillar hypertrophy. However, as the prevalence of obesity in youth has dramatically increased, it is now recognized as a significant contributor to OSAS, particularly in adolescence [1-3]. Further, there is a bidirectional relationship such that OSAS may promote further weight gain or may hinder weight loss efforts [42-48]. There are currently three interventions for weight loss: lifestyle modification altering diet and/or physical activity along with behavior change procedures, pharmacologic and surgical modalities. Often pharmacologic and surgical therapies are paired with lifestyle modification strategies. However, these are more limited in the pediatric population, reserved for the most severely obese and most often delayed until adolescence. We will discuss the three main modalities of weight loss as they relate to sleep with a primary focus on OSAS. Their impact on sleep duration, sleep architecture, and insomnia will also be discussed.