Perhaps there are no exceptions when it comes to indulging in “just one” fatty meal.

A single junk food meal is all it takes to damage your arteries, according to two Canadian studies, one by researchers at the Montreal Heart Institute’s EPIC Center and another by researchers at the Libin Cardiovascular Institute of Alberta.

The first study, out of Montreal, reached that conclusion after enlisting the help of 28 non-smoking men and getting them to eat two very different meals.

The first was a Mediterranean-style meal of salmon, almonds and vegetables cooked in olive oil. Just over half the calories in the dish came from fat, mainly monounsaturated and polyunsaturated.

A week later, the men were given a second meal. This time, the dish consisted of a sausage sandwich, an egg, a slice of cheese and three hash browns -- a meal similar to some fast-food breakfasts.

The second meal was loaded with saturated fat, and contained no Omega-3 fats.

The participants received ultrasounds after each meal so researchers could monitor how the foods had affected their vascular endothelium, the inner lining of the blood vessels.

Researchers, led by the University of Montreal’s Dr. Anil Nigam, found that the arteries of the study participants dilated 24 per cent less after the junk food meal.

By comparison, the researchers found that participants’ arteries dilated normally after the Mediterranean-style meal.

“We believe that a Mediterranean-type diet may be particularly beneficial for individuals with high triglyceride levels, such as patients with metabolic syndrome, precisely because it could help keep arteries healthy," Dr. Nigam said in a statement issued Tuesday.

The research has been published in the Canadian Journal of Cardiology.

The second study tested how the blood vessels reacted when a group of non-smoking university students began their day with a 900-calorie breakfast sandwich that had a whopping 50 g of fat.

Two hours after the students ate the sandwiches, the researchers found that their arteries’ ability to increase blood flow under stress had decreased by 15 to 20 per cent.

Lead study author Dr. Todd Anderson said if the arteries’ decreased capacity to increase blood flow under stress becomes a chronic condition, there is an increased risk of heart attack and stroke.

“The message is that completely normal individuals with no risk factors, these things can cause problems in the short term,” Anderson told CTV News. “And we should think more about what we put into our bodies.”

The findings were presented Tuesday at the Canadian Cardiovascular Congress.

Dr. Yoni Freedhoff of the Bariatric Medical Institute said he supports the underlying message that one high-fat meal can have an impact on the body.

However, he said his biggest concern is how people eat day in and day out.

“My advice to people all the time is, eat at home, make food at home,” Freedhoff told CTV.

“The food we eat when we purchase it outside the home contributes greatly to our weight and chronic disease.”

With a report from CTV’s medical specialist Avis Favaro and producer Elizabeth St. Philip