We examined the relationships between ED tendencies, SNS use intensity, and body esteem in Japanese and Chinese students. A total of 564 Japanese and Chinese 18-22-years-olds answered questions on basic demographics and completed the EAT-26, SNS Intensity Scale, BESAA, PHQ-9, and GAD-7.

First, this study (data collected in December 2021) shows that the number of people with a score ≥ 20 was higher (14.7% in Japan and 17% in China) than that in previous studies. A previous study in investigating ED tendencies reported that 8.7% of 494 junior college students in Japan had an EAT-26 score ≥ 20 in 2010 [24]. Another study using the EAT-26 reported a score of ≥ 20 in 59 (4.44%) of 1328 college students in Wuhu, China in 2015 [25]. Since the end of 2019, the coronavirus disease 2019 (COVID-19) pandemic has disrupted people’s daily lives and increased their anxiety, stress, and other negative emotions [26]. Moreover, those with mental disorders, including ED, could be affected in various ways. Therefore, we think the impact of COVID-19 may have resulted in a higher percentage of participants with EAT-26 scores of ≥ 20.

Second, we found gender differences in EAT-26 scores among the Chinese group, consistent with the literature which reporting that women have a higher ED risk than men in Western countries [27, 28]. This possibly reflects that Chinese women are more concerned about their body and weight than Chinese men and Japanese students.

In addition, Japanese women scored higher than Japanese men on the EAT-26, but this difference was not significant. Edman et al. similarly reported that there were no gender differences in the EAT-26 scores among Malaysian university students [29]. Research from Fiji shows that men also experience sociocultural pressure to achieve an ideal muscular body [30]. Thus, our findings suggest that Japanese men are at an equally high risk of developing ED as Japanese women.

The participants spent 31 min to two hours per day on SNS, compared to the average time of 16 min per day on Facebook reported in Japan in 2012 [31], and 15 min to 60 min per day on Weibo reported in China in 2012 [32]. Since 2019, because of the COVID-19 pandemic, many countries have restricted people’s daily activities and movements; for example, work and studying have been shifted to the home as much as possible, which could be one of the reasons for the increased time spent on SNS. Chinese students (M = 3.99, SD = 1.14) had significantly higher scores than Japanese students (M = 3.5, SD = 1.71) regarding time spent on SNS. We know that China ended the Zero-COVID policy in December 2022, much later than other countries, resulting in Chinese students spending more time working or studying at home; this may have increased their time spent on SNS. Increased time spent on SNS and the inability to control the use of SNS negatively impact people’s lives [33, 34].

It is worth mentioning that Chinese students reported higher scores on the BESAA than Japanese students. Heine et al. found that self-esteem is lower in Japan than in Western countries [35], but Chinese college students have been known to report high self-esteem, as in Western countries [36, 37]. In China, the only-child policy is currently in effect, and Chinese children receive a great deal of parental attention and care [38], leading to high levels of self-esteem. Low self-esteem has been found to be reciprocally predictive of body dissatisfaction [39, 40]. The results of this study are consistent with our findings that Chinese students generally had higher body esteem than Japanese students.

According to Tables 2 and 3, when we explored the relationship between ED tendencies, SNS use intensity, and body esteem, the correlation coefficients were not high despite a strong correlation (p < 0.01). In past studies [41, 42], data with very low correlation coefficients but high correlations such as these have been observer; thus, we used these data.

We hypothesized that body esteem mediates the relationship between SNS use intensity and ED tendencies. Unexpectedly, we did not observe this relationship in Japanese students. Although much of the research suggests that frequent SNS use is association with body dissatisfaction, the manner of SNS engagement can also lead to different results. For example, users can search for any content they are interested in; some use SNS to view others’ posts and comment on them or for uploading personal pictures [43]. The way of engagement on SNS has been shown to play an important role in well-being [44]; for example, users who posted statuses with a negative feedback-seeking style were more likely to report body dissatisfaction and ED symptoms [45]. As such, future studies should focus on exploring the relationship between the manner of SNS engagement and ED.

Our findings also showed that greater SNS intensity was associated with higher body esteem, which was associated with lower ED tendencies in Chinese students. This result—a positive relationship between SNS intensity and body esteem in Chinese students—is contrary to most of the literature regarding SNS use and body dissatisfaction. In our study, the SNS Intensity Scale was designed without restrictions on which social media could be used. As we were aware that WeChat’s utilization rate is over 80% in China, we guessed that most Chinese participants would answer the SNS Intensity Scale with reference to WeChat.

WeChat is similar to LINE in Japan, mostly used to communicate with friends, upload photos, and comment on photos. It could be that those who use SNS regularly or who have more friends on SNS are more willing to socialize on social media, get information, or share their own opinions, thereby increasing their self-confidence, including body esteem. SNS is mostly used to post photos or comments; it is also possible that people gained more attention on SNS because of beautiful photos, which helps enhance their self-esteem [46, 47]. We consider this one of the reasons for the positive relationship between SNS intensity and body esteem in the Chinese students.

We did not examine the way individuals engage on SNS; this, together with the lack of clarity regarding which SNS was used, was among the main limitations of this study. In addition, findings should be understood in the context to several limitations. We asked Cross Marketing Inc. for distribution and collection, but the subjects recruited through this channel were those who have registered with this company, and it is not representative of the entire college student population. In the population, this study used convenience sample, and recruited subjects nationwide, but the sample size was relatively small and age range was narrow. Future research on this topic should incorporate a large, more diverse participant sample. In the methodology, this study was self-report questionnaire, which is a convenient method but carries the risk that the subjects did not make authentic completions.

Additionally, at the time of data collection, 29 individuals had a BMI > 30 kg/m2, and some Chinese students weighed up to 190 kg. In China, an alternative unit of measurement of weight is “catty” (1 kg = 2 catty). Therefore, we speculate that these unusual weight data are likely owing to the fact that the participants did not see that the weight was marked in kg when filling out the questionnaire, and mistakenly filled in the weight according to the “catty” unit of measurement.

The relationship between SNS use, ED, and body dissatisfaction was compared between the two Asian countries of Japan and China. This study also included men, adding to the scant evidence pertaining to men. First, the results for the Japanese and Chinese students indicate that the status of ED in Asian countries is gradually converging with that in Western countries. Most existing research on ED has focused on Western countries. Chinese students, whose access to Western media and influences is lower than that of Japanese students, reported more ED tendencies and a stronger association between SNS use and ED tendencies. Therefore, it is important to provide evidence of the relationship between SNS use and ED in Asian countries, especially those such as China with their unique SNS platforms.

Second, the ratio of studies on ED related to men and women has been 1:10; therefore, there is little data on men. However, owing to the aesthetic culture espoused on SNS, men are also becoming conscious of their body shape and weight, which increases their risk of developing ED. Therefore, it is extremely important to consider men in ED studies.