Your daily cup of coffee is making you fat.

Do you crave for a donut after having a cup of coffee? Blame the caffeine, suggests a study which found that the widely consumed stimulant tempers taste buds temporarily, making food seem less sweet.

Caffeine is a powerful antagonist of adenosine receptors, which promote relaxation and sleepiness.Suppressing the receptors awakens people but decreases their ability to taste sweetness, which may make them desire it more, say researchers.

“When you drink caffeinated coffee, it will change how you perceive taste – for however long that effect lasts,” said Robin Dando, assistant professor at Cornell University in the US.

“So if you eat food directly after drinking a caffeinated coffee or other caffeinated drinks, you will likely perceive food differently,” said Dando.

In the study published in the Journal of Food Science, one group sampled decaffeinated coffee with 200 milligrammes of caffeine added in a laboratory setting, making a strong cup of coffee. The stimulant was added to make that group’s coffee consistent with real-life amounts of caffeine.

The other group drank just decaffeinated coffee. Both groups had sugar added. Panelists who drank the caffeinated brew rated it as less sweet.

In a secondary part of the study, participants disclosed their level of alertness and estimated the amount of caffeine in their coffee. They reported the same increase in alertness after drinking either the caffeinated or decaffeinated samples, all the while panelists could not predict if they had consumed the decaffeinated or the caffeinated version.

“We think there might be a placebo or a conditioning effect to the simple action of drinking coffee,” said Dando.

“The act of drinking coffee – with the aroma and taste – is usually followed by alertness. So the panelists felt alert even if the caffeine was not there,” said Dando.

“What seems to be important is the action of drinking that coffee. Just the action of thinking that you have done the things that make you feel more awake, makes you feel more awake,” he said.