New research from the Max Planck Institute for Metabolism Research suggests that just smelling food may be enough to trigger fullness, at least in lean mice.
The study, published in Nature Metabolism, identified a brain circuit that connects the nose to appetite-related neurons in the medial septum, a part of the brain not previously linked to hunger. When mice smelled food, this circuit activated within seconds and helped reduce how much they ate.
But in obese mice, the same neurons didn’t respond. Smelling food didn’t lead to satiety and didn’t change how much they consumed.
Researchers believe this scent-triggered satiety may be an evolutionary tool.
“We think this mechanism helps mice in the wild protect themselves from predators,” said Janice Bulk, first author of the study. “By eating for shorter periods, they reduce their chances of being caught.”
The study adds to growing evidence that obesity changes how the brain processes sensory signals, including smell, and may disrupt built-in checks on appetite. In humans, research has shown mixed results: some studies suggest that certain food odors reduce appetite, while others show that people with overweight or obesity may actually eat more after exposure to food smells.
“Our study shows how much our daily-lives’ eating habits are influenced by the smell of food,” said Sophie Steculorum, senior author and research group leader. “Since we discovered that the pathway only reduces appetite in lean mice, but not in obese mice, our study opens up a new way to help prevent overeating in obesity.”
The study was funded by the Max Planck Society.