To the best of our knowledge, this is the first study to examine the effects of eating together online on reciprocal HRVusing objective parameters.
The first important finding in this study is that eating together online significantly increased HRV during eating, compared with eating alone, implying that eating together online enhanced autonomic functions during dieting.24,25 This is a favorable outcome for people who are not able to eat together, such as those who are admitted to facilities or hospitals, or physically separated from their families. Under the recent COVID-19 pandemic, hospitalized patients with cancer have been prohibited from being visited. Consequently, more than half of them reported feeling lonely27; further dissemination of eating together online is desirable.
The UMACL reported that eating together online resulted in significantly higher physical energetics and less tension postprandial than pre-snacking, indicating that these feelings of relaxation may affect autonomic function. A previous study using a self-administered questionnaire also reported that eating together induced a sense of relaxation in the survey using a self-administered questionnaire.12 Another study reported that significant loneliness reduces HRV.15 Therefore, our result regarding increased HRV following eating together online may indicate alleviated loneliness by confirming the presence of other people. Apparently, autonomic signals, such as electrocardiogram and electrodermal activity, were synchronized with each other because the strangers were in the same space without direct communication.28 This study does not conduct a direct comparison because of conversations; however, the visual presence in the same space, even online, may have reduced loneliness.
The second important finding of this study is that the pre-and intra-snack correlations of SDNN changes in eating in a pair online were statistically significantly stronger compared with those in eating alone. This suggests that eating together online may positively affect HRV through social interaction with other people. Notably, during the second half of eating in the eating together online group, the SDNN changes were synchronized in all pairs, including one pair whose SDNN scores were both negative. This suggests that the physiological synchrony of eating together online may have increased as the diet progressed.
Although the design of our study does not identify the cause of this effect on social interactions, relaxation may have contributed to the outcome of the UMACL. The feeling of relaxation heightened by conversations while eating together has been reported.8,10 One pair whose SDNN score was negative in the second half of eating might have had a mutually heightened sense of tension affecting HRV. Apparently, pairing with a person with a poor relationship is more likely to increase physiological synchrony as assessed by HRV than pairing with a friend.18 The report stated that the reason for this phenomenon was that, if relationships with others were poor, they tried to increase affinity to establish social affiliation. More than 80% were peers in this study; however, poor relationships may have influenced social interactions when they were not.
Lastly, unlike previous studies,8,9 there was no difference in ingestion between the two groups in our study. Previous studies state that the increased ingestion for eating together online groups are attributed to choosing and eating more types of food owing to social interactions with other people.8 However, this may have caused the viands in this study to become cookies.
This study has two limitations. The first is that in the eating-alone group, the element of conversation was missing in the assessment of its effects on autonomic nervous system functioning during eating. Second, the results of the study cannot be generalized because it was conducted among relatively young, healthy volunteers. Sociodemographic characteristics such as being prone to eating alone, the male gender, older age, and unemployment are listed.1