The MRI images showed a reduction in tongue fat volume as the primary link between weight loss and sleep apnea improvement. They also found correlations between sleep apnea improvement and a reduction in the size of certain muscles -- namely, a jaw muscle used for chewing, known as the pteroid, and muscles on the sides of the airway known as the pharyngeal lateral wall -- but not to the same extent as a reduction in tongue fat.

The researchers suggest future studies should explore whether certain diets or therapeutic treatment techniques can aid in reducing tongue fat for treating sleep apnea. They also explored the role genetics may play in causing sleep apnea, and suggested that people of certain ethnicities may be predisposed to having fattier tongues.

According to study leader Richard Schwab from the University of Pennsylvania’s School of Medicine, patients who suffer from snoring or sleepiness should be checked for sleep apnea.

"Primary care doctors, and perhaps even dentists, should be asking about snoring and sleepiness in all patients, even those who have a normal body mass index, as, based on our data, they may also be at risk for sleep apnea," Schwab said in a press release.