The rodents - which were engineered to lack a sense of smell, put on a high-fat diet and ate just much as their non-engineered counterparts - lost an average of 16 percent of their body weight. Mice with enhanced olfactory senses gained weight.

It seems the smell of delicious food is enough to make you gain weight.

"Weight gain isn't purely a measure of the calories taken in," lead researcher Andrew Dillin said. "It's also related to how those calories are perceived."

The results of Dillin and his team at the University of California, Berkeley, were published in the journal "Cell Metabolism" on Wednesday. They show the dramatic effect that the sense of smell had on weight loss in mice.

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Two rodents were fed the same high-fat diet and became obese. Then researchers took away one of the mice's sense of smell - and its weight dropped by about a third, to 33 grams. The other mouse maintained a weight of around 49 grams.

Most of the weight shed was fat, so Dillin and his colleagues looked closely at fat deposits.

"The mice with no sense of smell had turned on a program to burn fat," the biology professor said. "It's one of the most interesting discoveries to come out of my lab."

But before you consider turning this information into a new weight-loss concept, beware: it's unclear whether humans would arrive at the same results as the mice.