The simple answer to the question is lips get thinner due to lose in collagen just like skin does. To support that answer statement, here is an excerpt from Real Simple magazine website, a dermatologist in Bloomfield Hills, Michigan, D’Anne Kleinsmith, M.D. says that “the older you get, the less collagen you produce. And collagen, a protein that supports the body’s soft tissue, is what gives lips their pleasing plumpness. The sun’s ultraviolet rays can also cause collagen to break down and lips to thin.”
Going through many articles online talking about when one starts losing collagen, I could not find one exact answer. One article says at 25 years old, one will start producing collagen 1% less every year, but on another article says it starts at 30. Apparently, there seems to be no exact answer as stated by a Denver, Colorado based plastic surgeon Stephen A. Goldstein, MD on RealSelf.com, a community-driven website about aesthetics medicine and cosmetic treatments. Dr. Goldstein says that “your body will continue to produce collagen all your life, but as you get older, the amount of collagen produce will decrease. It is true that the older you get, the thinner your skin becomes. No one can really say definitively that collagen production slows at age 25. Rather, I believe that the way a person ages is largely dependent upon genetics. Look at the skin quality of the elder people in your family and you’ll have somewhat of an idea of the way you’ll age.”
I personally agree with Dr. Goldstein. Genetic plays a huge role. For example, at 65 years old, my mother has not done any botox, facelift and all kind of similar treatment, but her skin appear at least 10 years younger. Giving birth to three children did not give her any stretch marks at all. I know my late maternal grandmother also did not have stretch marks. I do not have it also.
Now, back to our topic on thinning lips, how to slow down that thinning (read: aging). Several resources confirm that lips can be cared liked skin.
1. Protect from sun. Wear SPF at least 30. There are lip balm with SPF on the market.
2. Apply lip mask. Click here for my post about lip mask.
3. Include protein in daily diet.
4. Drink enough water
Last but least, cosmetically, apply lip liner slightly outside your lip to give an illusion of fuller lips.