Did you know that our sense of smell can actually regulate how much weight we gain or lose? This has been confirmed by a recent study at the University of California, Berkeley, which was conducted on mice.
A group of mice were each given the same amount of food. Some of the mice could smell normally, others could not smell at all and others still had an enhanced sense of smell. The study found that the smell-deficient mice ate the same amount of fatty food as those that retained their sense of smell, however the latter ballooned to twice their normal weight.
The same pattern was found in mice with an enhanced sense of smell, but they put on even more weight than the mice with a normal sense of smell. The findings suggest that food smells play an important role in how the body processes calories.
It appears that there’s a link between the olfactory (smell) system and regions of the brain that regulate metabolism, such as the hypothalamus, however it remains unknown whether smell has an impact on neural circuits.
The study is one of the very first that shows that olfactory manipulation can have an effect on how the brain perceives energy balance, as well as how it regulates it.
Humans tend to lose their sense of smell due to aging, injury or diseases such as Parkinson’s, and often become anorexic as a result of doing so. This is due to the loss of pleasure in eating, which in turn can lead to depression and a further loss of appetite.
Published in the Cell Metabolism journal, the study implies that the loss of smell itself plays a role in dramatic weight fluctuations, and also suggests possible interventions for those who are experiencing a loss of their sense of smell, as well as those having trouble losing weight.
Researchers are theorizing that a lack of smell tricks the body into thinking it has already eaten. While searching for food, the body stores up calories, and then burns them off once a new supply of food has been secured.
In order to destroy the smell neurons in the mice’s noses, the researchers used gene therapy to disable it temporarily, however spare stem cells were retained so that the mice’s sense of smell could be returned to normal after a period of about three weeks.
The smell-deficient mice burned calories by turning their beige fat cells, which accumulate around thighs and midriffs in humans, into brown fat cells. This type of fat cell burns fatty acids to produce heat. Some turned almost all of their beige fat into brown fat to become lean, mean fat burning machines.
A downside found to the research was the large increases in noradrenaline levels seen in the mice. This is a stress hormone tied to the sympathetic nervous system, which could lead to a heart attack in humans when elevated levels of it are sustained over a period of time.
Although removing a human being’s sense of smell seems extreme, it might prove to be a viable alternative for those considering having stomach stapling or bariatric surgery to lose weight. The researchers have suggested wiping out an individual’s sense of smell for a period of six months, then allowing the olfactory neurons to regrow following the rewiring of their metabolic program.
People with eating disorders can have a hard time controlling the amount of food they eat, because they have a lot of craving. As a result, gaining control over the olfactory neurons is vital for modulating the neural pathway that regulates their cravings.
Content source: UC Berkeley
Images (including cover) by Deposit Photos.
