A new study by neuroscientists at Scripps Research reveals how cold temperatures trigger a brain circuit that makes mammals eat more to stay warm.
The cold truth about energy balance
When we are exposed to cold, our body automatically increases its energy expenditure to maintain normal body temperature. This process, called thermogenesis, consumes calories from fat and other sources. To compensate for this energy loss, we also feel hungrier and eat more. This is an adaptive mechanism that helps us survive in harsh environments, but it also prevents us from losing weight by cold exposure alone.
The brain switch for cold-induced appetite
The researchers wanted to find out how the brain controls this cold-induced appetite increase. They compared the activity of neurons across the brain of mice under warm and cold conditions. They found that most neurons were less active in the cold, except for a small cluster of neurons in the thalamus, called the xiphoid nucleus. These neurons became more active when the mice were cold and hungry, and less active when they were warm and fed.
The researchers also showed that these neurons act as a switch for cold-related food seeking behavior. When they artificially activated these neurons, the mice ate more in the cold. When they inhibited these neurons, the mice ate less in the cold. These effects were specific to feeding behavior and did not affect other activities.
The researchers traced the connections of these neurons and found that they project to another brain region called the nucleus accumbens, which is involved in reward and motivation. This suggests that these neurons signal the need for food reward when the body is in energy deficit due to cold.
The potential for new treatments
This study reveals a novel brain circuit that regulates appetite and energy balance in response to cold. The researchers hope that this discovery could lead to new ways to enhance the metabolic benefits of cold exposure or other forms of fat burning, without increasing appetite and food intake.
“If we can figure out how to decouple the appetite increase from the energy expenditure increase, we might be able to use cold therapy or other methods to boost metabolism and weight loss more efficiently,” says Li Ye, PhD, associate professor and senior author of the study.
The study also raises the possibility that this brain circuit is part of a broader mechanism that compensates for extra energy expenditure in other situations, such as exercise.
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