When I reported on the astronomical calorie counts of many chain restaurant meals, I concluded by saying that "one of these blowout meals is not going to kill you." One reader, however, suggested that that's not always true, citing the cardiovascular effects of one of the 1,700-calorie bombs I described.
He's right—a study in 2000 suggested that an unusually heavy meal quadruples the chances of a heart attack in the first two hours after eating. The author, Francisco Lopez-Jimenez, now a cardiologist at the Mayo Clinic in Rochester, Minn., says there are several potential explanations. First, big meals are usually high in fat. (The Cheesecake Factory's fried mac and cheese platter has more than three days' worth of saturated fat.) "Fat intake, particularly in large amounts, can change the functioning of the arteries," keeping them from expanding when they need to, he says.
Such a large amount of food also requires a lot of digestive activity, which means the gut needs more blood. So the heart has to work harder. Blood sugar and insulin output go up, and that may cause blood pressure to rise in some people, Lopez-Jimenez says. Finally, he says, big meals are often associated with drinking, smoking, and other celebratory activities that might increase heart risk.
Note, however, that you probably didn't see anyone keeling over at your local Applebee's the last time you stopped in for a 1,380-calorie quesadilla burger. The additional short-term risk that arises from having a big meal is about the same as from having sex and is less than that from a heavy workout, Lopez-Jimenez said when the study was released. (Of course, sex and exercise both have longer-term health benefits; scarfing down the Red Lobster Ultimate Fondue does not.) Your actual risk of a post-meal heart attack will depend on how susceptible you are in the first place—and that depends on your age, whether you have diabetes or high blood pressure, and other factors. And, cheer up; a study published in 2006 suggested you can erase some of the risk by taking a walk after a meal.
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Meantime, you're not likely to actually hurt your stomach or digestive system because even a big meal is digested slowly, by a coordinated and regulated process, says Mark DeLegge, a gastroenterologist at the Medical University of South Carolina and chair of the American Gastroenterological Association's nutrition and obesity program. "For most of us, gastric distention sends a message to the brain that says, 'Stop!' " DeLegge says, so you stop eating before you literally burst your stomach or experience other problems. Exceptions include binge or competitive eaters or people who have undergone surgery to remove part of their stomach. And large and fatty meals may increase acid reflux in people with heartburn, he says.
The biggest harm comes from the extra calories, which are much easier to take in than burn off. (A 150-pound person would have to run for about three hours at a 10-minute-per-mile pace in order to burn off 2,000 calories.) You have to eat an extra 3,500 calories or so to gain a pound, so even a monster meal isn't going to immediately show up on the scale. It's the long term that's the problem; unless you work it off or compensate by eating less, an extra 2,000 calories once a month adds up to almost 7 pounds over a year.