Holiday celebrations often revolve around eating, but people with restricted diets are more likely to feel lonely when they can't share in what others are eating, researchers have found.
Across seven studies and controlled experiments, the findings, published in the Journal of Personality and Social Psychology, found that food restrictions predicted loneliness among both children and adults.
"Despite being physically present with others, having a food restriction leaves people feeling left out because they are not able to take part in bonding over the meal," said study lead author Kaitlin Woolley, assistant professor at Cornell University in the US.
For example, in one experiment, assigning unrestricted individuals to experience a food restriction increased reported feelings of loneliness. That suggests such feelings are not driven by non-food issues or limited to picky eaters.
"We can strip that away and show that assigning someone to a restriction or not can have implications for their feeling of inclusion in the group meal," she said.
According to the researchers, further evidence came from a survey of observers of the Jewish holiday of Passover.
When reminded during the holiday of the leavened foods they couldn't enjoy with others, participants' loneliness increased.
Further evidence came from a survey of observers of the Jewish holiday of Passover. When reminded during the holiday of the leavened foods they couldn't enjoy with others, participants' loneliness increased.
Yet, within their own similarly restricted group, they felt a stronger bond. But when restricted from sharing in the meal, people suffer "food worries," said the researcher.
They fret about what they can eat and how others might judge them for not fitting in.
Those worries generated a degree of loneliness comparable to that reported by unmarried or low-income adults, and stronger than that experienced by school children who were not native English speakers, according to the research.
Compared with non-restricted individuals, having a restriction increased reported loneliness by 19 per cent. People felt lonelier regardless of how severe their restriction was, or whether their restriction was imposed or voluntary.
To date, Woolley said, children have been the primary focus of research on the effects of food restrictions.
A nationally representative survey she analysed from the Centers for Disease Control did not track the issue among adults.
But increasingly, Woolley said, food restrictions are being carried into adulthood, or adults are choosing restricted diets such as gluten-free, vegetarian and vegan for health or ethical reasons.
"Up to 30 per cent of all participants in the research deal with restrictions," Woolley said.