It's a sad day indeed when we learn the news that one of our favourite (yet diet-deadly) breakfast foods can actually kill us.

Sure, we've known for a long time that breakfast bacon ain't exactly diet food, but now we have proof of just how bad it is and just how quickly it can cause bad health.

According to a new study led by Dr. Todd Anderson, Heart and Stroke Foundation researcher and head of cardiac science at the University of Calgary, Canada, if you eat a breakfast high in fat (think: bacon, cheese etc) your body will be feeling the bad effects well before lunch.

Why? High-fat diets are associated with developing atherosclerosis over your lifetime. Atherosclerosis is a narrowing of the arteries that can cause serious problems including heart disease, stroke or even death.

And just one day of eating a breakfast high in fat results in unhappy blood vessels, says Dr. Anderson, so it's time to strike bacon, cheese and high-fat buns from the breakfast menu.

Delegates at the Canadian Cardiovascular Congress heard yesterday about a study at Dr. Anderson's lab, led by student researcher Vincent Lee. The key ingredients: breakfast sandwiches and a group of healthy, non-smoking university students.

The study measured the effects of just one high-fat meal on microvascular function - an indicator of overall vascular (or blood vessel) health.

The students were studied twice, once on a day they had no breakfast, and once on a day when they consumed two commercially available breakfast sandwiches which had a total of 900 calories and 50 g of fat. Two hours after eating the sandwiches, their VTI (or blood flow) had decreased by 15-20 per cent, reports Dr. Anderson.

"VTI tells us how much blood flow you can you get in your arm," says Dr. Anderson. The higher the better, which means the small vessels can dilate to capacity, and the blood vessel hormones are working well. Therefore a decrease is a bad sign.

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

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

"This study reminds us that our behaviours are the backbone of preventing heart disease," says Heart and Stroke Foundation spokesperson Dr. Beth Abramson.

"Remember that whether you eat at home or go to a restaurant, you're still in charge of what you eat. So consider all the choices, and try to cut down on saturated and trans fats, calories and sodium. That's one of the keys to decrease your risk of heart disease and stroke."

Source: Heart and Stroke Foundation of Canada