Where a low-calorie drink is still as sweet as the normal version, the mismatch appears to send metabolisms haywire.
The body has evolved to burn more calories if something tastes sweet because in nature sweeter substances contain more energy.
Tam Fry, of the National Obesity Forum, added: "This research should be enough to convince you that artificial ingredients, whether they be in food or drink, can screw up your system even though they may sound healthy". These sweeteners are less in calorie, but the consequences are more which includes diabetes.
Senior author Prof Dana Small said: "A calorie is not a calorie. Either may affect metabolic health".
Batch with diet soft drink consumption resulted in eating more as their brain did not register calorie count.
In the new study, brains of 15 participants, when they drank diet drinks were scanned and were then compared with regular beverages.
The study was published August 10 in the journal Current Biology.
Scientists say diet foods and artificial sweeteners may trigger weight gain and increase the risk of diabetes, as their sweet taste fools the body's metabolism into believing that we are consuming more calories.
As said by Mr. Dwyer, the most vital complication lies in the fate of the calories that are taken in the mismatch condition.
"These are not efficiently metabolised at the time of ingestion and thus processed later and/or stored either of which could drive weight gain and interfere with metabolism". British experts, who are unconvinced about the study, are of the opinion that people who are concerned about taking diet drinks should stick to drinking water.
But Professor Tom Sanders, of King's College London, said: "Saying a calorie is not a calorie is gobbledegook". He commented that the findings of the study are not supported by observational proof on long-term consumers of artificial sweeteners. He argues that artificial sweeteners can not cause weight gain.