Just 90 minutes later, they noticed that in men, blood flow to the brain had slowed.
William Dunn, who performed scans on volunteers, told the Daily Record: "We've shown that eating a sugar and fat-laden snack can actually affect blood flow to the brain within minutes.
"This reduction in the reactivity of blood vessels in the brain has previously been linked to an increased stroke risk - but the changes we observed were modest."
However the researchers noticed no difference in the blood flow to women's brains.
Writing in the Scottish Medical Journal, Mr Dunn and his co-author, Professor Matthew Walters, stroke consultant at Glasgow's Western Infirmary, said: "The deep-fried Mars Bar has been cited as 'all that is wrong with the high-fat, high-sugar Scottish diet'."
"It is also a snack that the international community strongly associates with Scotland."
The pair investigated the effect on blood flow to the brain after eating either a deep-fried Mars Bar or porridge.
Scotland-wide, 22 per cent of fish and chip shops sell the snack, according to a report in The Lancet medical journal.
The recipe was devised at the Carron Fish Bar in Stonehaven, Aberdeenshire, in 1992, when a young boy asked for "a Mars Bar supper".
Ann Straiton, manageress at the time, thought he was joking and threatened to throw him out. When he said he was serious, she battered one and popped it in the fryer. It was served with a portion of chips and went down a treat.
Lorraine Watson, the current owner, told the Record she still sells up to 150 bars a week.
London restaurant, the Grill On The Square in Leicester Square, also sells deep-fried Mars bars.
Chef Daniel Smalley told the Daily Mail: "The secret to getting it right, is to make sure that the batter (flour, bicarbonate of soda, soda water, salt and a small amount of food colouring) is kept very cold.
"It needs to be around zero degrees. That's what makes it so crisp and light."
The bar should be immersed in the fat for between 60 and 90 seconds in a fryer set to 170c.
"And, no, we don't use the same fryer that we use to cook our fish."
He added: "If you enjoy chocolate, it's one of the best things to eat. It's such a complex taste: all that hot caramel, fudge and melted chocolate.
"And then you've got the textures: the crunch of the batter alongside the gooiness of the chocolate and caramel.
"Just make sure you don't eat anything else for the rest of the week."
- Daily Mail
