DIET softdrinks and artificially sweetened foods trick the brain into making you fatter and could even trigger diabetes, a new study suggests.
The body has evolved to burn more calories if something tastes sweet because in nature, sweeter substances contain more energy.
But diet products that do not taste sweet confuse the brain into thinking there are fewer calories to burn than there are.
This causes the body’s metabolism to drop, storing up the products as fat, claim researchers at Yale University in the US.
Senior author of the study, which has been published in the journal Current Biology, Professor Dana Small said: “A calorie is not a calorie.
“When sweet taste and energy are not matched, less energy is metabolised and inaccurate signals go to the brain. Either may affect metabolic health.”
Scientists scanned the brains of 15 people who consumed diet drinks and others who drank regular ones. They also monitored how much energy was burned and found that when there was a “mismatch”, the brain did not register that calories had been consumed, which could lead to eating more.
“In other words, the assumption that more calories trigger greater metabolic and brain response is wrong,” Prof Small said. “Calories are only half of the equation; sweet taste perception is the other half.”
Researchers found that many processed foods contain such mismatches, such as yogurt flavoured with low calorie sweeteners.
“Our bodies evolved to efficiently use the energy sources available in nature,” Prof Small told Yale News.
“Our modern food environment is characterised by energy sources our bodies have never seen before.”
However, not everyone is convinced.
Professor Tom Sanders, of King’s College London, said: “Saying a calorie is not a calorie is gobbledegook.”