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Losing your sense of smell could be the weird secret to losing weight

9Coach logo 9Coach 9/07/2017 Sam Downing

Today in weird science: Scientists have discovered that mice lacking a sense of smell lose fat faster than smelly mice, even if both eat the same amount of food. © studio2sim/Shutterstock Today in weird science: Scientists have discovered that mice lacking a sense of smell lose fat faster than smelly mice, even if both eat the same amount of food. Today in weird science: Scientists have discovered that mice lacking a sense of smell lose fat faster than smelly mice, even if both eat the same amount of food.

"It's one of the most interesting discoveries to come out of my lab," admitted Andrew Dillin, a professor of molecular and cell biology at the University of California, Berkeley, in a statement.

His team initially assumed that mice who couldn’t smell ate less — but it turned out they were eating the same calories as mice who could smell.

When two groups of mice were put on the same high-fat diet, both became obese. But when one group’s sense of smell was switched off, they dropped about a third of their bodyweight.

"I never expected turning off smell would have such dramatic weight-loss effects," Dillin said.

There turned out to be differences in the two types of fat the mice carried: brown fat, which your body burns to generate heat; and white fat, which is stored for energy (and is the kind you pack on when you consume excess calories).

The no-smell mice’s brown fat was actively burning, and they were converting their white fat to brown fat — which Dillin likened to switching on “a program to burn fat”.

More research is needed to find out exactly why this happens, but it could be down to a link between smell and the sympathetic nervous system (aka the fight-or-flight response), because the no-smell mice had high levels of adrenalin in their blood. 

Intriguing sidenote: Dillin mentioned his results to a German scientist who’d bred a “super-smelling mouse” (scientists do weird stuff), which put on even way more weight than a regular-smelling mouse despite eating the same amount.

Sense of smell has an established influence on appetite and food intake. People are more sensitive to smells when they’re hungry than after they’ve eaten, and those who lose their sense of smell — because of age, injury, or disease — often become anorexic.

None of this means you should deliberately ditch your sense of smell as a quick weight-loss trick, but the research suggests weight loss and weight gain goes beyond how much you eat.

“Sensory systems play a role in metabolism. Weight gain isn’t purely a measure of the calories taken in; it’s also related to how those calories are perceived,” said Dillin.

“If we can validate this in humans, perhaps we can actually make a drug that doesn’t interfere with smell but still blocks that metabolic circuitry. That would be amazing.”

“We think olfactory [smell] neurons are very important for controlling pleasure of food and if we have a way to modulate this pathway, we might be able to block cravings in these people and help them with managing their food intake,” added fellow researcher Céline Riera, of Cedars-Sinai Medical Center.

The research is published in the journal Cell Metabolism.

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