One hypothesis proposed by this team of researchers suggests
"that sharing of regurgitated food, a process called trophallaxis, may be a way for morsels of food to become more digestible. Alternatively, it may be that social interaction affects some neural pathways that promote gastrointestinal activity, notes Keller. But Dr Ken Cheng, a behavioral biologist at Macquarie University has another explanation in mind, involving gut microbes. 'It would not surprise me if gut bacteria, which would be passed around with the exchange of food, played a role as well in the adverse effects of isolation,' says Cheng, who was not involved in the research."
This study on ants shows that social isolation and health are closely related and much more research is needed in this area. It's notable that "even ants" show a negative reaction to loneliness, as do many other species, including humans. It should also be noted that because ants show such negative responses to social isolation, they should not any longer be forced to live alone.