My two cents from the medical field: The big guys are definitely at risk for obstructive sleep apnea. It has to do with soft tissue in the neck and pharynx that obstructs the airway during sleep. The lack of air during sleep actually causes them to stop breathing for short times. Very severe cases can cause respiratory failure. Some symptoms are obesity, daytime sleepiness, morning headaches, falling asleep quickly during the day, snoring. It can be picked up by a sleeping partner who notices the snoring and periods of apnea (not breathing).
Sleep apnea is not just a nuisance. Untreated, it can affect the heart and lungs over time and even lead to heart failure.
It's diagnosed with a sleep study. People are watched at a sleep center and their breathing is monitored for periods of apnea and low oxygen levels.
Treatments are weight loss, CPAP breathing mask at night which provides some pressure with breaths to keep the airways open. Extreme cases can have surgery to remove some tissue from the soft palate that can be obstructing the airway.