Photo: Joshua Rappeneker, Flickr

We know fatty foods can take a toll on our waistlines and our health. But how bad is just one unhealthy meal? It's a nutritional trainwreck, as Yunji De Nies and Jon Garcia from ABC News found out.

De Nies and Garcia set out to determine the effect just one meal has on the body. So they headed to the University of Maryland Medical Center, where their blood was analyzed and their arteries were examined before and after they ate a meal consisting of deep fried macaroni and cheese, quesadilla burger and monster-sized deep dish sundae. Pre-meal test results: Both were perfectly healthy.

Things didn't look so great after they each worked at consuming nearly 6,190 calories and 187 grams of fat (the USDA recommends 2,000 calories and no more than 20 grams of saturated fat per day). While neither could finish their massive portions, what they did manage to eat made them both feel tired and sluggish, and Garcia got a severe headache. Then, after two hours and post-meal testing, Garcia's blood samples were very cloudy -- the fat was literally flooding his system. De Nies' blood sample was not as startling, but the ultrasound of her arteries revealed her heart was working so hard to pump blood through her narrowing arteries, she could actually hear the difference -- you can hear it too, in this video.

What's the significance of this mini-test? "It shows that one meal can affect the health of your arteries," says The University of Maryland's Dr. Robert Vogel. His colleague, Dr. Michael Miller, says eating high-fat foods is as bad as smoking cigarettes.

Although the effects of this one meal lasted just six hours, experts warn that if eaten regularly, unhealthy meals can lead to heart attacks and a variety of other health problems.

"Each and every meal is important to the health of our arteries and since we live by our arteries, your survival depends on it," says Vogel.