Really want fries with that? Just blame it on your brain
The brain has a "sixth sense" that can detect calories in food without the benefit of taste or smell, an American study suggests.
The Yale University research, published today in the journal Neuron, says this independent sensing mechanism can switch on a desire for food and be a contributing factor in weight gain and obesity.
"Basically, we show that animals can develop a preference for caloric foods even if there is no taste or flavour information associated with it," said Yale neuroscientist Ivan de Araujo, the lead author.
"Something in the brain is sensing it," he said.
The research further showed that the parts of the brain programmed to sense when calories are being consumed is located in one of its pleasure centres.
"The parts of the brain that are known for pleasant sensory stimuli ... the reward pathways, are also responsive to calories even if there is no taste information or palatability linked to them," de Araujo said.
He said elevated levels of glucose found in the blood after taking in food calories likely trigger the production of the neurochemical dopamine.
The dopamine then triggers a response in the ventral striatum causing it to take note of the incoming calories and to create a pleasurable response.
Because this sensory response is pleasurable, it may play a key role in dieting and obesity.
"In dieting you can try to substitute a caloric eating style with a version that is less caloric, but otherwise tastes equally good," de Araujo said. "But this, in the long run, might not be sufficient to curb caloric consumption."
For example, de Araujo explained, switching to diet pop may cut calories but the sugar-free beverage would not produce the pleasurable response wanted in the brain. So the dieter might unwittingly try to produce it in other ways.
"They might simply compensate by getting more calories out of other sources," he said. "The lack of calories will provide the brain with some negative signal ..."
The Yale study used caged mice that had their ability to taste sweets removed. They were then given two drinking choices, water sweetened with sucrose and the plain variety.
De Araujo said the mice chose the sugared water, indicating they were somehow sensing the presence of calories even without taste buds.
Source: Toronto Star