High air temperature can lead to weight gain despite reducing appetite, according to research published in the scientific journal Communications Biology.
Researchers found that warm ambient conditions prompt the body to spend significantly less energy maintaining its internal temperature. This drop in caloric expenditure can outweigh the reduction in food intake caused by a heat-induced loss of appetite.
In experiments conducted on animals, scientists identified a specific group of neurons within the hypothalamus that respond directly to rising environmental temperatures. When these nerve cells were activated, the animals experienced an increased feeling of satiety and began consuming less food.
However, the decrease in energy required for thermoregulation was even greater than the reduction in food intake. As a result, the overall energy balance shifted toward a surplus, causing the animals to gain weight despite eating smaller portions.
Brain control and thermal regulation
The hypothalamus is a small structure located near the base of the brain that plays a critical role in maintaining homeostasis. It acts as the command center for key biological functions, including body temperature, thirst, hunger, sleep, and hormone regulation. Satiety refers to the physiological state of feeling full after eating, which normally signals an organism to stop food consumption.
Warm-blooded creatures rely on thermoregulation to maintain a constant internal core body temperature regardless of their surroundings. In colder environments, the metabolic rate increases as the body burns calories to generate heat through thermogenesis. Conversely, in warm conditions, heat production decreases, leading to lower total daily energy expenditure.
Communications Biology is an open-access, peer-reviewed scientific journal published by Nature Portfolio. It publishes high-quality research and reviews spanning all areas of the biological sciences, including cellular biology, neuroscience, and physiology.
Scientists involved in the study indicated that ambient air temperature may be an underestimated factor influencing body mass. They noted that the findings could help explain how prolonged stays in heated or temperature-controlled indoor spaces impact energy balance over time.
Future research and human impact
The researchers emphasized that the newly discovered neural mechanism has so far only been demonstrated in animal subjects. Further investigation will be needed to determine how pronounced this thermal effect is in human physiology and how it might inform weight management strategies.
The discovery follows earlier research into dietary interventions and metabolic health. In a previous study, scientists found that matcha tea reduces pathological changes in heart tissue caused by obesity.
