Why does fresh air make us hungry?

Now We Know: Ghrelin is a hormone in our blood which is believed to be connected to appetite

What is it about taking a long hike or swimming in the sea that makes a toasted cheese sandwich or a bag of fish and chips taste so darn good? It’s common knowledge that exercise burns calories, but does the fresh air or type of activity have an impact on our appetite? What is it about fresh air and outdoor activities that makes us hungry?

When taking a deep dive into this question, it’s important to consider that a by-product of exercise in general is a link to the levels of acylated ghrelin in our system. Ghrelin is a hormone in our blood which is believed to be connected to appetite, and it is activated in varying degrees by different types of exercise.

A 2017 study by Prof David Stensel at the School of Sport, Exercise and Health Sciences at Loughborough University in England found that shorter and less intense bouts of exercise meant less acylated ghrelin was being repressed. If you compare a strenuous bout of intentional aerobic exercise with a family walk in the woods, the findings of this study argue that you may feel more hungry after the light hike.

When it comes to fresh air specifically, there could be a number of factors at play that might make you feel peckish. It could be down to the type of activity you’re engaged in; are you lolling around the poolside or are you kayaking around coastal sea caves? You can take an educated guess on which one of those activities burns more energy.


Temperature is an important factor in considering why we feel hungry after spending time in the fresh air. Is it cold outside? If so, our bodies will engage in burning energy in an effort to stay warm. Some researchers point to our primitive hard-wiring which makes us eat more in the cold.

Speaking to NPR.org, Ira Ockene, cardiologist at the University of Massachusetts Medical School, says: “we are driven by things implanted in our brain a long, long time ago.” Ockene’s research has found that caloric intake tends to increase in colder weather.

It could be argued that this is why sea swimming, particularly in cold waters, can be an especially effective way to maintain a healthy weight, even while increasing our appetite. Besides, it’s common knowledge that hunger is the best sauce for any meal.