A study finds that dining companions may play a role in calorie consumption. 

It seems that women choose foods with fewer calories when they are eating with men, than they do if they are eating alone or with girlfriends.

Canadian researchers observed college students on the sly at meal times for four days over the course of a week.

From a short distance, they watched a total of 469 people in 198 groups, some eating alone, and some eating with others, and recorded what food items were brought to each table and by whom.

They discovered that women chose foods with significantly fewer calories when they were eating with men. And the more men at the table, the fewer calories on women’s plates.

For example, when dining in pairs, women chose meals with an average of 670 calories when they were eating with another woman, but meals of only 550 calories when dining with a man. When women would eat with men in larger groups, the calorie counts of their meals went down further, to an average of 400 to 450 calories.

Women eating solo fell somewhere between the two extremes, putting an average of  570 calories on their plates.

The results, which were published online in the journal Appetite, are in line with previous studies that have demonstrated the profound impact of environmental cues, including the presence of other people, on what and how much gets eaten at mealtimes.

Researchers at Georgia State University in Atlanta, for example, have shown that meals eaten with one other person were, on average, 33 percent larger than those eaten alone. And consumption increases incrementally for each person added to the group.

The current study was one of the first, however, to look at the influence of gender roles on food choices. 

“As soon as you throw a man in the mix, the caloric value of what women were eating decreased, “ says Meredith Young, a PhD candidate in psychology, neuroscience and behavior at McMaster University in Ontario, who led the research.

She says the findings suggest women are conditioned to perceive smaller portions of food as more feminine. And whether they realize it or not, they feel that choosing meals with fewer calories will make them more attractive to men.

Men’s food selections did not appear to be substantially affected by the number or gender of their dining companions.

“I think it’s fascinating because so much of our eating is, I think, based not on physical appetite, whether we need food or not, but on the conditions under which we are operating,” says Dr. Lawrence Cheskin, MD, director of the John’s Hopkins Weight Management Center in Baltimore.

And even though scientists only looked at what people brought to the table, not what they ate, he says the study is still useful.

“If you are eating with an eye to what other people are thinking of you, you simply won’t bring things to the table that you think would be viewed negatively. So it is a reasonable surrogate for what people are consuming when they finish the meal,” he explains.

“I think the message here is that who you are eating with and who you are, influences your choice. It’s not purely based on your hunger and your body’s need for food," Dr. Cheskin says.

"If you want to change your food habits, don’t just change them in front of members of the opposite sex," he says.