The Fascinating Reason We Lose Our Appetite When It's Hot Outside

The weather dictates a lot of what you do — how much activity you pursue, how often you step outdoors, and what clothes you choose to wear in the morning. Did you know, however, that it also directs your hunger levels?

Whether you've realized it consciously or not, when it's hot outside, you don't really feel as hungry as you do in the colder months. In fact, it's natural for you to lose your appetite in the summer months, craving cooling beverages or lighter foods instead. And according to science, this has a lot to do with our brains (the hypothalamus), how our body digests food, and what happens as a result of it (thermic effect of food). 

The thermic effect of food refers to how our bodies use up energy to digest, absorb, and metabolize what we consume. In the hotter months, our bodies have a way of naturally wanting to keep cool, which results in us having a smaller appetite (because less calories means less energy/heat expended in the process of digesting food). As explained by registered dietitian and associate professor of nutritional sciences at Texas Tech University, Allison Childress to Verywell Health, "People in warmer climates typically eat fewer calories, because eating those calories actually produces heat and can warm the body up even more." The brain also has a part to play in this strange thing that happens to your body in the summer.

Scientists believe that this natural order of needing to stay cool by eating less when it's hot outside is something that has evolved over time in humans. Our brains play a big role in the loss of appetite too. 

According to Dr. Alona Pulde, a family practitioner who specializes in nutrition and lifestyle medicine, (via Yahoo Life), "The hypothalamus, a region in the brain responsible for both regulating our temperature and our hunger, is especially busy during the summer months ... Because digesting food generates heat, the hypothalamus suppresses our appetite to prevent additional heat from building up in our body." 

This might also explain why we feel drawn to cool drinks and lighter meals during the hot summer months. Understanding what sorts of foods expend more energy while being digested and what we should and shouldn't be eating can help us stay comfortable, cool, and healthy when it's hot outside. And just because the heat makes it more tempting to go out and buy yourself some ice cream, that doesn't mean you're making the right choice for your body. In fact, things like ice cream might make you feel good temporarily because of their cool temperature. But with their high sugar (calorie) content, they actually have a high thermic effect overall. So what foods should you be eating when it's hot outside and you lose your appetite? 

Hydration is key during the hot months. However, that doesn't mean you have to only consume water. While water is a great source of fluids and there are recommended amounts you should aim toward consuming (15.5 cups for men and 11.5 cups for women daily), you can't discount the value of consuming fruits and vegetables with a high water content. These include watermelons, strawberries, cucumber, celery, lettuce, oranges, tomatoes, bell pepper, etc. In fact, fruits are great for those times when you have no appetite.

"Higher temperatures and humidity increase the speed of evaporation from the skin which means we sweat more. Therefore we need to replenish our fluid levels more often and more frequently. How much more you need really depends on your personal circumstances as well as how active you are," shared nutritionist Kerry Torrens with BBC Good Food. 

And even though high-fiber foods like whole grains, broccoli, spinach, and kale, and protein-rich foods like chicken, beef, eggs, lentils, dairy, and seafood do have a high thermic effect, this doesn't mean you should be cutting those out of your diet entirely. As Childress explained to Verywell Health, "It's still important to keep a varied diet, making sure you're not eliminating anything just because of the heat is important." You can cut out high-calorie options like ice creams, candy, and even some overly sweet desserts in the hot months. Swap them out for healthier versions – like fruit or vegetable smoothies instead.