Why Do You Lose Your Appetite During a Heat Wave?

Excessive heat can make you feel nauseous, weak, or dizzy. You might even lose your appetite when it’s sweltering outside.

A 2021 case study from China found that a 1-degree Celsius (1.8 degrees Fahrenheit) increase in temperature may decrease food intake by 0.11%. While this study focused on consumer behavior rather than biological mechanisms, experts say there is a scientific explanation for why people lose their appetite in a heat wave.

“When we’re in a heated environment, we actually have less of an appetite and consume fewer calories as a way of cooling our body,” Allison Childress, PhD, RDN, a registered dietitian and an associate professor of nutritional sciences at Texas Tech University, told Verywell.

She said many factors besides temperature can influence appetite, but there are “definite differences” in how many calories people consume in hot and cold weather.

“People in warmer climates typically eat fewer calories, because eating those calories actually produce heat and can warm the body up even more,” Childress said.

The amount of heat produced from digesting is known as the “thermic effect of food,” she said. High-protein foods have the greatest thermic effect, so things like chicken, beef, beans, eggs, lentils, and seafood might warm you up the most as you start digesting.

“We don’t want to eliminate them altogether, but we want to definitely be aware that those things might increase our body temperature a little bit more,” Childress said.

Loss of appetite is a symptom of heat stroke and may be accompanied by a high fever, rapid heart rate, nausea, and confusion. As the heat index continues to reach dangerous levels across the country, it’s important to know what foods can help you stay healthy and hydrated.

What Can You Eat to Cool Off During a Heat Wave?

When planning a heat-wave grocery list, you’ll want to consider hydration along with the thermic effect of food.

Sweating is the body’s way of staying cool, but sweating too much without replenishing fluids can lead to dehydration, which can then contribute to heat exhaustion, the formation of kidney stones, and other health concerns.

Some of the most hydrating foods are melons, berries, lettuce, celery, lettuce, tomatoes, cucumbers, and yogurt, according to Gordon Fisher, PhD, FACSM, a professor of kinesiology at the University of Alabama at Birmingham.

“Foods can provide between 20–30% of our daily fluid intake, thus we can also stay hydrated by increasing our intake of foods that have higher water content such as fruits and vegetables,” Fisher told Verywell in an email.

He said drinking six to eight glasses of water or other fluids can help replenish the amount lost on hot days. This isn’t a hard-and-fast rule, and everyone has different fluid needs. The amount an individual needs to stay hydrated is based on a variety of factors like activity level, age, and amount of time spent in the heat.

“During hot days, most individuals lose between 2–2.5 liters of fluids throughout the day,” Fisher said.

Athletes or people who work outside all day in the heat might want to consider adding sports drinks to their hydration schedule to help replace the electrolytes lost in sweat. But for most people, water is enough as long as they eat meals and snacks to help replace salt, according to the Centers for Disease Control and Prevention.

What Foods Should You Avoid in a Heat Wave?

Frozen treats might sound like the best option during a heat wave, but these might actually make you feel hotter in the long run, according to Childress.

“When we eat a popsicle or drink a very cold beverage, we get some immediate relief. But if there are calories in that popsicle, or if there are calories in that beverage, we’re going to digest them, which is going to start that thermic effect of food cycle. And so we will end up increasing our body temperature eventually,” Childress said.

Foods that take more energy to digest, like protein and fiber-rich foods, will also warm the body up as they’re being digested. But cutting out nutrient-rich foods isn’t the answer, especially for people who are pregnant, lactating, or malnourished. Instead, Childress recommends focusing on staying hydrated and eating nutrient-dense foods to stay cool and safe during a heat wave.

“It’s still important to keep a varied diet, making sure you’re not eliminating anything just because of the heat is important,” Childress said.