There's a reason why there have been countless song and movie titles that include the sun. Little feels better after a long, frigid winter than feeling a beam of warm sun shining down from the sky come spring and summer. But as good as that sun might feel, you're probably well aware that it can do a number on your skin health. (Reminder: Slather up with SPF early and often!)
And for certain people, a new study in the July 2022 edition of the journal Nature Metabolism suggests, sun exposure might impact appetite as well. Sunshine—in particular UVB rays—can lead men to seek out more food and consume more calories; for women, the rays seem not to play a role.
What This Appetite Study Found
As a refresher, two types of ultraviolet radiation created by the sun's energy can harm skin cells, the Skin Cancer Foundation confirms.
UVA rays dive deeper and lead to skin aging, and make up about 95% of total UV rays that hit the Earth.
UVB rays cause surface damage and skin burns.
While sunshine does have some potential health benefits—including reducing blood pressure, releasing mood-improving endorphins and bone-bolstering vitamin D and possibly lowering risk for heart disease—it's the No. 1 risk factor for skin cancer.
To land at their conclusion about spiked summer appetites, researchers at Tel Aviv University used data from about 3,000 adults aged 25 to 64 enrolled in the National Health and Nutrition (MABAT) surveys. They studied the individuals' dietary intake reports over a 12-month period, then tabulated the average monthly energy consumption for men and women. The verdict from this pool of participants:
Men eat approximately 300 calories more per day during summer (2,188 calories per day March to September; 1,875 calories per day October to February)
Women report eating about the same year-round (1,507 calories per day March to September; 1,475 calories per day October to February)
To dive in further, the researchers enlisted five men and five women between 18 and 55 years of age, and exposed each to UVB rays for 25 minutes. They took blood samples before and after, and the scientists found that exposure to this particular type of ultraviolet radiation changed the metabolism-associated proteins in men differently from women.
After the five-day sun exposure study, males demonstrated an increase in levels of the "hunger" hormone ghrelin in the blood and females didn't. Why? The scientists believe that the DNA damage from the UVB rays triggered the release of ghrelin via a particular hormonal pathway in men. In women, estrogen (one of the main sex hormones, and one that's more prolific in women's bodies than men's) appeared to "block" this pathway so ghrelin could not be released.
Ghrelin, by the way, has more than one function. It stokes your appetite, and, in turn, your food intake. It's also known to play a role in fat storage, energy regulation, nerve activity and muscle strength.
Keeping a steady blood sugar is a good way to help keep your hunger hormones, like ghrelin, at appropriate levels. To help our body's blood sugar levels stay more consistent, be sure to include a source of protein, fiber and healthy fat to give your meals and snacks some staying power. But hunger is not something to be feared, and if your body is wanting more energy in the summer months it's perfectly OK to honor that hunger.
The Bottom Line
According to this preliminary study, increased exposure to UVB rays might alter men's metabolisms, and men and women appear to respond differently to seasonal changes in sunshine levels.
It's important to note that the researchers used cisgender terms as a generalization. More studies are clearly needed to tap a more diverse study group, as well as a larger one (10 people for the blood test is very few) and to track this in more accurate ways than a self-reported dietary log (which is easy to fib about or make a mistake on). It would also be beneficial to have each person track their time spent outdoors (rather then just assuming more time spent outside during summer), as UVB rays cannot penetrate glass.
Age, genetics, activity level and a whole slew of other health conditions can impact hormone levels, too. So before you start hiding from the sun in an attempt to inspire your hangries to hit the road, if you find yourself feeling ravenous frequently, try to focus on blood sugar stability throughout the day and fill up with these 35 high-volume, super-satisfying recipes. And if you still struggle with a growling stomach, work with a registered dietitian—you might not be eating enough.