On hot, sweaty, muggy summer days, you may notice that you’re not as hungry as you are in cooler weather. But what is the relationship between temperature and appetite? Why do we feel less hungry when it’s hot?
Impact of temperature The effect on appetite has long been observed by scientists: “What we know is that people in cold environments take in more calories.” Allison Childressa registered dietitian and associate professor at Texas Tech University, told Live Science.
There is a fundamental biological reason for this. calorie Food is a unit of energy that, when burned, releases heat and helps keep you warm in cold weather. But when winter ends and the weather gets warmer, “people find that they’re a lot less hungry,” a trend Childress has seen in both her clinical practice and her research. In the broader scientific literature.
But the mechanism behind this phenomenon is unclear, as many factors influence calorie intake, Childress said.
Matt CarterCarter, a neuroscientist at Williams College in Massachusetts, agreed: Many variables, including hormones, proteins and environmental factors, influence how and why we feel hungry and, ultimately, why we feel less hungry on hot days, he said.
Related: What is the maximum temperature the human body can withstand?
Our body always tries to stabilize the internal state. HomeostasisThat is why we drink water when we sweat in the hot sun or after strenuous exercise. Hunger also plays a role in maintaining homeostasis, so when the body does not have enough calories, we feel hungry, and when we eat, we feel full, which helps maintain the balance of the physiological state in the body.
Many homeostatic processes are maintained by hormones that act as chemical messengers in the body. When it comes to appetite and satiety, two hormones play a major role. GhrelinIt is expelled when the stomach is empty Leptinis secreted by fat cells and tells the brain that the body is full.
These hormones send signals to the hypothalamus, the part of the brain that helps regulate body temperature, hunger, and thirst, to affect our emotions and behavior. At the base of the hypothalamus is a cluster of specialized neurons that “control hunger and fullness,” Carter says. There, ghrelin stimulates hunger-related neurons, AgRP neurons, which make you feel hungry. In contrast, leptin inhibits these neurons and stimulates POMC neurons, which make you feel full.
But how temperature affects this complex system is “still an area of research,” Carter said. The brain has temperature sensors and proteins that change shape when the body reaches a certain temperature. E-Life A 2020 study found that in mice, cold temperatures cause certain brain cells to send signals to AgRP neurons, making them feel hungrier.
On the other hand, when it’s hot, POMC neurons contain heat-sensing proteins that become activated when body temperature rises, which in turn activates neurons related to satiety, according to a 2018 study published in the journal Neuroscience. PLOS Biology.
“But it’s probably not the only thing,” Carter says: other brain circuits likely work together to influence how much we eat.
Childress noted that there are likely other factors at play. “You have biological mechanisms for heat and cold, but it’s also important to know that sometimes you eat foods that exceed those biological mechanisms to a certain extent,” she said. Sometimes we lose the ability to listen to our body’s cues, for example, overeating when we’re full or not eating when we’re hungry.
Childress said that no matter what your symptoms are, it’s important to stay hydrated in the summer, whether that’s by eating water-rich foods like vegetables and fruits or drinking liquids. Counterintuitively, frozen foods are often high in calories, which can increase your body temperature.
Hot or not, appetite is an intricate balance—our body’s way of tuning into its environment. “Eating and drinking seems like something that just happens,” Carter says. “But in reality, your brain is gauging exactly how many calories, fluids, and optimal body temperature you need, which I think is amazing.”
