Ever wonder why the lower eyelids sag with age?

Many theories have sought to explain what causes the baggy lower eyelids that inevitably come with aging, but a recent study suggests the primary culrpit: fat expansion in the eye socket.

UCLA researchers looked at MRIs of 40 subjects (17 males and 23 females) between the ages of 12 and 80. What they found was that the lower eyelid tissue increased with age and that the largest contributor to this size increase was fat increase.

As a result, the researchers say, fat excision should be a component of treatment for patients seeking cosmetic surgery.

Currently, many plastic surgeons performing procedures to treat baggy eyelids do not remove any fat at all. They reposition the fat or conduct more invasive tightening of the muscle that surrounds the eye, or they tighten the actual ligament that holds the eyeball in place, according to a UCLA press release.

"A common treatment performed in the past and present is surgical excision of fat to treat a ‘herniation of fat’ — meaning that the amount of fat in eye socket does not change but the cover that holds the fat in place, the orbital septum, is weakened or broken and fat slips out," the study’s lead author, Dr. Sean Darcy, said. "However, our study showed there is actually an increase in fat with age, and it is more likely that the fat increase causes the baggy eyelids rather than a weakened ligament."

Co-author Timothy Miller hopes plastic surgeons take this study seriously. According to a report from the American Society of Plastic Surgeons, eyelid surgery (aka blepharoplasty) is the fourth most popular procedure in the United States.

"Our findings may change the way some plastic surgeons treat baggy eyes," Miller said. "Our study showed that a component of a patient’s blepharoplasty procedure should almost routinely involve fat excision rather than these procedures."

The new findings are published in the September issue of the Journal of Plastic and Reconstructive Surgery.