Final answer:
Obesity affects PFTs by decreasing lung volumes, increasing airway resistance, and contributing to sleep-disordered breathing.
Step-by-step explanation:
Obesity has several effects on pulmonary function tests (PFTs). One effect is the decreased lung volumes, such as reduced total lung capacity (TLC) and forced vital capacity (FVC). This is because the excess fat around the chest and abdomen restricts the movement of the diaphragm and lungs, making it harder to take in deep breaths. Another effect is the increased airway resistance, which can lead to difficulties in exhaling air forcefully. This is due to the inflammation and narrowing of the airways caused by obesity. Additionally, obesity can contribute to sleep-disordered breathing, such as obstructive sleep apnea, which can further affect PFTs.