VANCOUVER - Just one day of eating a fat-laden breakfast sandwich, processed cheese and meat on a bun, and "your blood vessels become unhappy" well before lunch, according to a Canadian research presented Tuesday.

The study, presented at the Canadian Cardiovascular Congress 2012, provided an insight into how quickly the damage of high-fat diets can start.

In order to assess the acute effects of just one high-fat meal on microvascular function, an indicator of overall vascular (blood vessel) health, researchers designed a study that involved a group of healthy, non-smoking university students, and breakfast sandwiches.

The students were studied twice, once on a day they had no breakfast, and the other on a day when they consumed two commercially available breakfast sandwiches, total of 900 calories and 50 g of fat.

Two hours after eating the sandwiches, their VTI (velocity time integral), one important gauge of how "happy" the arteries feel, had decreased by 15-20 percent, according to Dr. Todd Anderson, whose lab conducted the research.

"VTI tells us how much blood flow you can you get in your arm," said Anderson. "The higher the better, which means the small vessels can dilate to capacity, and the blood vessel hormones are working well."

From just one isolated meal, the results are temporary. But the study showed that such a high-fat offering can do more harm, and do it more quickly, than people might think, the researchers said.

"I won't say don't ever have a breakfast sandwich," said Anderson. "But enough of a diet like that, and you can see how you can build up fat in the walls of your arteries."

High-fat diets are associated with developing atherosclerosis, or narrowing of the arteries, over a lifetime, which can lead to serious problems including heart disease, stroke or even death, according to the researchers.