Rationale: Obesity is an increasing childhood epidemic in Canada. Obstructive sleep apnea (OSA) is a complication of obesity which causes cardiovascular disease, reduced quality of life, and premature death. While the complex interactions between obesity and OSA are not entirely clear, we hypothesize that these conditions may compound each other by:

1. decreasing physical activity and total energy expenditure by reducing both non-exercise physical pursuits (NEAT- non-exercise activity thermogenesis) and purposeful physical activity.
2. alterations in the secretion of appetite-controlling hormones, which may lead to increases in energy intake.

Objective: To determine whether the presence of both obesity and OSA in children is associated with a decrease in physical activity and alterations in appetite-regulating hormones greater than those seen in either condition alone or compared to controls.

Methods: Comparison of children 10-17 years with obesity and OSA, obesity alone, OSA alone and neither condition, for the following outcomes: (1) NEAT (kcal/day) (2) Physical activity behavior, appetite regulating hormone profile and self-report appetite assessment.

Unique Aspects: This study combines expertise in sleep medicine, exercise physiology and obesity. Conclusions from this study will better characterize this high-risk clinical population so that innovative strategies targeting improvements in lifestyle behaviors can be developed.

Inclusion Criteria:

• age 10-17 years
• coming for polysomnography at the Children's Hospital of Eastern Ontario

Exclusion Criteria:

• children receiving treatment for OSA with CPAP (continuous positive airway pressure) or bi-level therapy
• craniofacial abnormalities
• genetic syndromes
• neuromuscular disease
• tracheostomy
• medications that may affect appetite or energy balance (systemic corticosteroids)

Subjects will be recruited from those scheduled to undergo polysomnography in the sleep laboratory at the Children's Hospital of Eastern Ontario