Why do fat people have a higher tendency to suffer sleep apnea?

Neck. Overweight patients tend to have more soft tissue around their neck and inthe back of their throat. Both neck size and the narrowness of a patients airway are risks for sleep apnea.
Extra fat & flesh. Obesity can cause obstructive sleep apnea (osa). A person with osa may not have enough space in the throat area, so air can't flow easily to the lungs during sleep. An obese person has more fat, including in the neck and throat areas, so there is more flesh to block air flow. An obese person lying down has extra weight in the tummy pushing up at the bottom of the chest, making breathing more work.
Sleep Apnea. Obesity causes increase in the parapharyngeal soft tissue and narrow air space causing increased obstruction to airflow increasing the risk for apnea.