Researchers developed ways to temporarily eliminate the sense of smell in adult mice and discovered that those mice that lost smell could eat a high-fat diet and stay a normal weight, while littermates that retained the sense of smell ballooned to twice normal weight.
Super- smellers gained more weight than did normal mice on the same high-fat diet. Smell-deficient mice burned excess fat instead of storing it, suggesting a link between smell and metabolism.
In addition, mice with a boosted sense of smell — super-smellers — got even fatter on a high-fat diet than did mice with the normal smell.
The findings suggest that the odour of what we eat may play an important role in how the body deals with calories. If you can’t smell your food, you may burn it rather than storing it.
These results point to a key connection between the olfactory or smell system and regions of the brain that regulates metabolism, in particular, the hypothalamus, through the neural circuits are still unknown.
“This paper is one of the first studies that really show if we manipulate olfactory inputs we can actually alter how the brain perceives energy balance, and how the brain regulates energy balance,” said Céline Riera, a former UC Berkeley postdoctoral fellow now at Cedars-Sinai Medical Center in Los Angeles.
Humans who lose their sense of smell because of age, injury or diseases such as Parkinson’s often become anorexic, but the cause has been unclear because the loss of pleasure in eating also leads to depression, which itself can cause loss of appetite.
The new study, published this week in the journal Cell Metabolism, implies that the loss of smell itself plays a role, and suggests possible interventions for those who have lost their smell as well as those having trouble losing weight.
