Conventional wisdom says you can pretty much eat whatever you want if you’re an avid runner, as your body is burning off all of the excess calories. But is that really true? New research now suggests that avid runners need to pay attention to their diets as well when it comes to the potential for heart disease.

As a 10-mile-a-day runner, Dave McGillivray thought he could eat whatever he wanted without worrying about his heart. “I figured if the furnace was hot enough, it would burn everything,” said McGillivray, who is 59.

But a diagnosis six months ago of coronary artery disease shocked McGillivray, a finisher of 130 marathons and several Ironman-distance triathlons. Suddenly he regretted including a chocolate-chip-cookie recipe in his memoir about endurance athletics.

“My first reaction was, I was embarrassed,” he said.

As race director of the Boston Marathon, McGillivray is a high-profile exhibit in a growing medical case against the devil-may-care diets of many marathoners. Their high-mileage habit tends to lower their weight, blood pressure, heart rate and cholesterol levels, leading them (and sometimes their doctors) to assume their cardiac health is robust regardless of diet.

“‘I will run it off’—that attitude clearly prevails among the marathoners themselves, almost sometimes to an arrogance,” said Paul Thompson, a veteran marathoner who is chief of cardiology at Hartford Hospital.

A growing body of research shows the error of that thinking. A study published in the current edition of Missouri Medicine found that 50 men who had run at least one marathon a year for 25 years had higher levels of coronary-artery plaque than a control group of sedentary men. A British Medical Journal study published this year compared the carotid arteries of 42 Boston Marathon qualifiers with their much-less active spouses. “We hypothesized that the runners would have a more favourable atherosclerotic risk profile,” says the article. As it turned out, that hypothesis was wrong.

Many assumed that extreme-endurance sports could help prevent heart disease, but now the research suggests this extreme activity may actually cause problems.

We should be careful of course to jump to conclusions after several studies, but certainly this raises questions and challenges old assumptions.

It also brings us back to some common sense notions that moderation in diet and excercise can be the best combination. Pushing anything to the limit – whether its your diet or your activities, can lead to risks.

Married people are more prone to obesity. That’s one of the negative health realities of marriage, though there are positives as well. In trying to understand why this is so, here’s an interesting nugget from a recent article.

People eat more when they’re together. A 1992 study that asked participants to record their food consumption for a week found that eating with one companion increased meal size by 41 percent compared with eating alone, while breaking bread with six or more people increased an individual’s caloric intake by a whopping 76 percent. Other studies have found somewhat more modest increases, but the effect is remarkably consistent.

Why do we eat more when we eat with others? It may be a result of social norms. Communal meals tend to last longer than eating solo, and people who sit in front of food can’t resist eating it. Another possible explanation is our habit of mimicking our dining companions: When they take a bite, we take a bite. More people means more cues to eat. The habit may, alternatively, lie deep in evolutionary history. Chimpanzees and marmosets spontaneously share food, probably to help form social bonds. From the innocent, altruistic act grew a regrettable human custom. Perhaps you feed (and feed, and feed) your spouse to strengthen your marital bond, even if you’re ultimately shortening its duration.

Think about your own eating habits. You might be able to make a real difference in your food consumption and overall health just by being more conscious of who you eat with and how often you do that. Finding more opportunities to eat alone can potentially have significant results!