A Prehistoric Foraging Strategy May Be Why We Eat More Around Friends, Study Suggests

The amount of food people eat tends to be profoundly influenced by the company they share while taking their meal, and may be linked to evolutionary psychology, a study led by researchers from the University of Birmingham found.

The study, published in The American Journal of Clinical Nutrition on October 4, was based on a meta-analysis of 42 previously conducted studies into the "social facilitation" of food consumption, according to a release from the University of Birmingham in England.

The analysis found that a person's meals could be 29 to 48 percent larger when they ate with friends as opposed to when they ate alone, according to the British Psychological Society. Another study found that a person consumed an average of 23 percent more calories when they ate with company.

However, the social facilitation effect of people eating more when they were with others could not be observed when the people in question were strangers to one another.

"People want to convey positive impressions to strangers," explained Helen Ruddock, the psychology researcher at the University of Birmingham who led the project. "Selecting small portions may provide a means of doing so and this may be why the social facilitation of eating is less pronounced among groups of strangers.

Our tendency to eat more food when we are with people we know may be a vestige of the lives of our prehistoric hunter-gatherer ancestors, the research team suggested. Like their ancient counterparts, modern humans tend to share a food source. The inner mechanisms that once abetted the foraging of our ancestors may continue to exert profound influence on our dietary behavior today.

This is called an "evolutionary mismatch"—humans are hardwired to unconsciously employ a foraging strategy that would have been vital to the survival of their prehistoric predecessors, but which mostly just causes excess caloric intake today.

Even so, the research found evidence that certain people or demographics may feel prompted to eat less around others, given the situation.

Women, for example, were found to eat less food in the company of men, regardless of whether those men were strangers or loved ones. Obese or overweight people could eat around 18 percent less around others.

"Findings from previous research suggest that we often choose what (and how much) to eat based on the type of impression that we want to convey about ourselves," Ruddock said. "Evidence suggests that this may be particularly pronounced for women eating with men they wish to impress and for people with obesity who wish to avoid being judged for overeating."

Buddhist monks eat during the Pchum Ben festival (festival of death) at a pagoda in Phnom Penh on September 16. People change their eating habits when in the presence of others. Tang Chhin Sothy/Getty