Apparently your tongue is fat. I mean that there is a normal amount of fat within your tongue muscle. And if you have obstructive sleep apnea (OSA), you may have too much tongue fat. At least according to this recent study. Researchers used sophisticated MRI scans to compare the overall volume and amount of fat in the tongues of overweight men with and without OSA. The results showed that the more obese the subject, the larger the tongue and the higher amount of fat in the tongue. There was also a significant association between belly fat and tongue fat. Patients with OSA had more tongue fat than in the control patients. They also had higher tongue volumes and a higher percentage of tongue fat. There was also an association between the sleep apnea severity and the tongue volume as well as amount of tongue fat.
The amount of fat was greatest in the back of the tongue rather than the front of the tongue in the patients with OSA. This makes sense anatomically because the back of the tongue is involved in blocking off the upper airway during sleep apnea. Another interesting finding was that the researchers examined the chewing muscle and it did not have a higher percentage of fat. This means that when patient's have extra weight, it's not deposited uniformly in the neck and head, but only in certain areas.
Finally, the researchers suggest that the increased amount of fat in the tongue in those with OSA can inhibit the way the tongue normally moves out of the way to allow air to flow.