Eating late can affect your circadian rhythm for the worst, leading to skin damage


Researchers at the University of Texas Southwestern Medical Center recently made an interesting discovery—one that could give you pause next time you crave a midnight snack. They found that eating late at night could possibly make you more vulnerable to sunburn and sun damage, along with all the long-term effects of exposure to ultraviolet rays, including premature skin aging and cancer.

It’s a fascinating link, to say the least. But as summer approaches, it might be an important thing to keep in mind. Here’s how this particular study went and what it means for you…

The Far-Reaching Effects of the Circadian Clock

As you may know, the body’s circadian clock (or rhythm) is the 24-hour internal clock that tells you when to wake up, be alert, get drowsy, and go to sleep. The circadian clock is your body’s central clock (located in a tiny region of the brain’s hypothalamus) and it controls many other peripheral clocks. These peripheral clocks govern the rest of your cells—and I mean each and every cell, from your brain and liver cells to your fat and skin cells, and everything in between. The central clock is responsible for keeping all the peripheral clocks in sync with the Earth’s rotation.

The circadian clock also controls a host of body functions. According to this study, “The direct and indirect targets of the circadian clock encode key regulators of many, if not most, biological processes, including metabolism, cell proliferation, and response to therapeutic treatment.”

Research has shown that the circadian clock even plays a role in skin biology and aging. In addition to processes like the hair growth cycle, it regulates how the skin responds to ultraviolet radiation from the sun. It does this in part by controlling the release of an enzyme called XPA, which is involved in the repair of your DNA. XPA levels are higher during the daytime hours and significantly lower at night. In fact, the skin is more likely to develop a tumor overnight because the release of reparative XPA is so low in the evening hours.

Despite all these links between the circadian clock and skin that researchers do know about, less is known about outside factors that influence the clock/skin connection. For instance, fasting has been shown to change factors related to the circadian clock, but whether or not the time you eat affects the skin has never been examined…until now.

Researchers took it upon themselves to investigate whether food intake/restriction can change the skin’s “daily clock.” In other words, could eating at times that go against your internal clock affect your skin, and if so, how?

They divided mice into five groups and fed each of them on different schedules:

  • Unlimited access to food
  • Early daytime feeding
  • Midday feeding
  • Early night feeding
  • Late night feeding

The results showed that the mice that ate only during the day (which is not typical for them, considering they are nocturnal) sustained more skin damage when exposed to UVB radiation. (the sun’s UVB rays  burn the superficial layers of the skin and are involved in the development of skin cancer.) Part of the explanation for this is that the enzyme XPA shifted its normal daily cycle and was less active during the day—which is when it is usually at its peak.

On the other hand, mice that ate at night (as they usually do in nature) did not have altered XPA cycles, so they were less likely to suffer UVB sun damage.

The researchers wrote, “This work shows that time of feeding is an important regulator of skin function… Our results indicate that timing of food intake has a more pronounced influence on skin biology than previously recognized, representing a modifiable regulator of skin health.”

While it’s still too early to know if this discovery applies to humans, researchers believe that what time of day or night you eat may very well:

  • Shift the phases of your skin’s circadian clock;
  • Alter the release of enzymes (like XPA) and other genes that usually function during the daytime hours; and
  • Cause significant changes in your skin.

What Does This Mean For You?

This study provides further proof that messing with your body’s internal clock can have far-reaching consequences.

Another example of this is the health dangers posed by nightshift work. The body innately wants and needs sleep at night when it’s dark. If this doesn’t happen every night as it should, the repercussions can be disastrous. Long-term nightshift work, and the corresponding shift in circadian rhythm, increases the risk of cardiovascular disease, diabetes, obesity, depression, infertility, and cancer.

In the case of this study, the solution is pretty simple: Curb your late-night snacking. I know this can be hard to do if you get a craving for something sweet. But one suggestion I give my patients is to brush and floss their teeth right after dinner. After putting forth the effort to floss, especially, most people decide it’s not worth it to eat again.

It also helps to include a good amount of protein in your dinner. One study found that eating high-protein meals during the day cut cravings by 60 percent and the hankering for a late-night snack by 50 percent.

If the craving just won’t die, make yourself a hot cup of green tea (unsweetened, of course) or drink a tall glass of water. Sometimes the body confuses thirst for hunger, and drinking something stops the hunger pangs.

If there’s one thing that’s becoming more and more clear, it’s that you can’t trick your body into going against its innate internal clock. So instead of fighting your circadian rhythm, try to live your life in accordance to it. Your health will be better for it.



Last Updated: August 16, 2018
Originally Published: May 17, 2018