Study: Vacationing in Chicago this week from Europe, Jelle den Burger and Nirusa Naguleswaran grabbed a bite at the Dog House Grill: a classic Italian beef sandwich for him, grilled cheese for her.

Both think the way their genders lined up with their food choices was no coincidence. Women, said Naguleswaran, are simply more likely to ditch meat, and to care about how their diet affects the environment and other people.

"I don't want to put it in the wrong way, that male people feel attacked," said Naguleswaran, of Netherlands, laughing. She said she used to love eating meat, but giving it up for climate reasons was more important to her. "We just have it in our nature to care about others."

Now, scientists can say more confidently than ever that gender and meat-eating preferences are linked. A paper out in Nature Scientific Reports this week shows that the difference is nearly universal across cultures — and that it's even more pronounced in countries that are more developed.

Researchers already knew men in some countries ate more meat than women did. And they knew that people in wealthier countries ate more meat overall. But the latest findings suggest that when men and women have the social and financial freedom to make choices about their diets, they diverge from each other even more, with men eating more meat and women eating less.

That's important because about 20% of planet-warming global greenhouse gas emissions come from animal-based food products, according to earlier research from the University of Illinois. The researchers behind the new report think their findings could fine-tune efforts to persuade people to eat less meat and dairy.

"Anything that one could do to reduce meat consumption in men would have a greater impact, on average, than among women," said Christopher Hopwood, a professor of psychology at the University of Zurich and one of the authors of the paper. The work drew on surveys funded by Mercy for Animals, a nonprofit dedicated to ending animal agriculture. Hopwood said he is not affiliated with the organization and is not an advocate.

Researchers ask what thousands eat

The researchers asked over 28,000 people in 23 countries on four continents how much of various types of food they ate every day, then calculated the average land animal consumption by gender identity in each country. They used the United Nations Human Development Index, which measures health, education and standard of living, to rank how "developed" each country was, and also looked at the Global Gender Gap Index, a scale of gender equality published by the World Economic Forum.

They found that, with three exceptions — China, India and Indonesia — gender differences in meat consumption were higher in countries with higher development and gender equality scores.

The large number and cultural diversity of people surveyed is "a real strength of this," said Daniel Rosenfeld, a social psychologist at UCLA who studies eating behavior and moral psychology and was not involved in the study.

The study did not answer the question of why men tend to eat more meat, but scientists have some theories. One is that evolutionarily, women may have been hormonally hardwired to avoid meat that could possibly have been contaminated, affecting pregnancy, whereas men may have sought out meat proteins given their history as hunters in some societies.

But even the idea of men as hunters is intertwined with culture, Rosenfeld said. That's a good example of another theory, which is that societal norms shape gender identity from an early age and thus how people decide to fill their plates.

'I'm going to eat more'

Rosenfeld, who said he stopped eating meat about 10 years ago, said his own experience hanging out in college "as a guy hanging out with other guy friends" illustrated the cultural pressure for men to eat meat. "If they're all eating meats and I decide not to," he said, "it can disrupt the natural flow of social situations."

The same cultural factors that shape gender influence how people respond to new information, said Carolyn Semmler, a professor of psychology at the University of Adelaide in Australia who also studies meat eating and social factors such as gender. Semmler was not involved in this study. In some of her past work, she's studied cognitive dissonance around eating meat.

In those cases, she said, women presented with information about poor animal welfare in the livestock industry were more likely to say they would reduce their meat consumption. But men tended to go the other direction, she said.

"One participant said to me, 'I think you guys are trying to get me to eat less meat, so I'm going to eat more,'" she said.

Semmler said meat can be important to masculine identity, noting for example the popular notion of men at the grill. And she said presenting eating less meat as a moral cause can be a sensitive issue. Still, she said, people should be aware of how their food choices affect the planet.

But she and Hopwood acknowledged how difficult it is to change behavior.

"Men are a tough nut to crack," Hopwood said.

Jose Lopez, another diner at the Dog House Grill, said he thought men should eat less meat but said that in general he has observed otherwise.

"We're carnivores," he said. "Men eat like savages." VOA/SP