Food plays hard to get (yum-yum)

JOHNS HOPKINS (US) — Having to work hard for food makes it taste better, a study with mice finds.

The results suggest that putting in extra effort to get fed can enhance appreciation—even for fare we might ordinarily not favor, such as low-fat, low-calorie foods. The findings are reported in the journal Proceedings of the Royal Society B.

“At present, we don’t know why effort seems to boost the taste of food,” says Alexander Johnson, an associate research scientist in the Department of Psychological and Brain Sciences at Johns Hopkins University. “But we know that it does, and this effect lasts for at least 24 hours after the act of working hard to get the food.”

The results hold out hope that people who struggle to maintain a healthy weight could be conditioned to consume lower calorie foods, says Johnson, who led the study. They may also provide insight into methods of altering other less-than-optimal behavior, he adds.

Johnson and colleagues, using ordinary laboratory mice, conducted two experiments. In the first, mice were trained to respond to two levers. If the mice pressed one lever once, they were rewarded with a sugary treat. Another lever had to be pressed 15 times to deliver a similar snack.

Later, when given free access to both tidbits, the rodents clearly preferred “the food that they worked harder for,” Johnson says.

In the second experiment, the team wanted to ascertain whether the animals’ preference for the harder-to-obtain food would hold if those morsels were low-calorie. So half the mice received lower calorie goodies from a high-effort lever, and half got them from a low-effort lever.

When both groups of mice were given free access to the low-calorie food later, those who had used the high-effort lever ate more of it and even seemed to enjoy it more than did the other group.

“We then analyzed the way in which the mice consumed the food,” Johnson says. “Why did we do this? Because food intake can be driven by a variety of factors, including how it tastes, how hungry the mice were beforehand, and how ‘sated’ or full the food made them feel.”

Researchers used licking behavior as a measure of the rodents’ enjoyment of their treats, and found that the mice that had to work harder for their low-cal rewards did, in fact, savor them more.

“Our basic conclusion is that under these conditions, having to work harder to get a certain food changes how much that food is valued, and it does that by changing how good that food tastes,” Johnson says.

“This suggests that, down the road, obese individuals might be able to alter their eating habits so as to prefer healthier, low calorie food by manipulating the amount of work required to obtain the food. Of course, our study didn’t delve into that aspect. But the implications certainly are there.”

The study was funded by grants from the National Institute of Diabetes and Digestive and Kidney Diseases and the National Institute of Mental Health.

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