Many factors such as hormones, proteins, and the environment influence how and why humans feel less hungry when the weather is warm.
Scientists have long examined the impact of temperature on appetite. “What we know is that people in colder environments tend to consume more calories,” said Allison Childress, a nutrition expert and associate professor at Texas Tech University. There is a biological reason for this. Calories are a unit of energy, and burning calories can generate heat, helping people maintain their body temperature in cold weather.
People feel less hungry when the weather warms up. (Photo: Vaya).
However, as winter passes and the weather warms up, people notice they feel much less hungry. Scientists are still unclear about the exact mechanisms behind this phenomenon. Childress noted that many factors influence calorie intake.
Matt Carter, a neuroscientist at Williams College in Massachusetts, agrees with this perspective. According to him, many variables—including hormones, proteins, and environmental factors—affect how and why people feel hungry, as well as why that sensation decreases when it’s warm.
The human body always strives to maintain stable internal conditions, known as homeostasis. That is why people sweat under the scorching sun or drink water after strenuous exercise. Hunger is also part of homeostasis. People feel hungry when their bodies are low on calories and full after eating.
Frozen treats like ice cream can actually raise body temperature because they are often high in calories. (Photo: PM Images).
Many homeostatic processes are regulated by hormones, which act as “messengers” in the body. Two hormones, ghrelin and leptin, play significant roles in hunger and satiety. The stomach releases ghrelin when hungry. Leptin is secreted by fat cells, signaling to the brain when the body is full.
These hormones communicate with the hypothalamus, the part of the brain that regulates aspects such as body temperature, hunger, and thirst. Carter explained that at the base of the hypothalamus is a cluster of specialized neurons that coordinate feelings of hunger and fullness. There, ghrelin stimulates neurons associated with hunger, known as AgRP. Meanwhile, leptin inhibits these neurons and activates POMC neurons, inducing the sensation of fullness.
However, how temperature affects this complex system still requires further investigation. The brain has temperature sensors that are proteins that change shape when the body reaches a certain warmth. A study published in the journal eLife in 2020 found that in mice, certain brain cells transmit information to AgRP neurons when temperatures drop, increasing feelings of hunger.
According to another study published in PLOS Biology in 2018, POMC neurons have a type of temperature-sensing protein that is activated when body temperature rises. But Carter noted that other neural circuits may also work together to influence the amount of food people consume.
“Humans have biological mechanisms influenced by temperature, but one important thing to know is that we can sometimes ignore these biological mechanisms,” Childress said. Sometimes people lose the ability to listen to their body’s signals, such as overeating or not eating when they are hungry.
Childress emphasized that in the summer, it is essential to keep the body hydrated, whether by consuming water-rich foods like fruits and vegetables or drinking water directly. Frozen treats like ice cream can actually raise body temperature because they are often high in calories.
