Why do you feel less hungry when it's hot out?

In the sweaty, sticky, dog days of summer, you may notice that you're not as hungry as you are in cooler weather. But what's the connection between temperature and apPetite? Why do we feel less hungry when it's hot out?

The iNFLuence of temperature on apPetite has long been observed by scientists. "What we know is, people in colder environments eat more calories," Allison Childress, a registered dietitian and associate professor at Texas Tech University, told Live Science.

There's a basic biological reason for this. Calories are a unit of energy; burning them off can release heat, helping people maintain their body heat in colder climates. But as the winter gives way to warmer weather, "people notice that they are a lot less hungry" — a trend Childress has seen in both her clinical practice and in the broader scientific literature.

The mechanisms behind this phenomenon, however, are unclear. Many factors influence caloric intake, Childress said.

Matt Carter, a neuroscientist at Williams College in Massachusetts, agreed. Many variables — including hormones, proteins and environmental factors — affect how and why we feel hungry and, ultimately, why that feeling diminishes on hotter days, Carter said.

Related: What's the hottest temperature the human body can endure?

Our bodies are always trying to keep internal conditions stable. This is called homeostasis. It's why we sweat in the scorching sun or drink water after a strenuous workout. Hunger is also homeostatic; we feel hungry when our body is low on calories and feel full after eating a meal, keeping our inner physiological state balanced.