Prevalence of underweight and overweight
Results show that 45.3% of the participating female university students in Vietnam were underweight. The previous national surveys from 1992 and 2002 reported that the percentage of underweight females between the ages of 18 and 34 were 30.5% and 30.3%, respectively . The research by Cuong et al.  showed that the prevalence of underweight females in Ho Chi Minh City was 20.4%, and the survey from Hanoi in 2004 showed 22.4% underweight females between the ages of 25 and 34 .
The percentage of underweight females in the current study is higher compared to findings of previous studies. One possible explanation for this result may be related to factors influencing the development of disordered eating such as an increased exposure to Western culture, higher education levels, and socio economic development in Hanoi. Vietnamese students may focus more strongly on the body ideal from Western countries; for example, they might believe that body thinness is necessary to be successful in modern society. Another possible explanation could be that since 2008 the capital city Hanoi has grown two to three times because of the addition of the Hatay province. Therefore, the universities in Hanoi have more students coming from areas outside of the city whose family members are farmers with low incomes. The families have to pay tuition fees as well as room and board for their adult children when they go to the university in Hanoi. However, often their incomes are not sufficient to cover all the costs for the students living in Hanoi. This could be one of the reasons why some students become underweight since they can not afford a proper diet. This might also explain the results found in the surveys.
Previous studies conducted in Vietnam revealing the prevalence of underweight Vietnamese adults in urban areas as well as a growing prevalence of overweight individuals seem to indicate an important public health problem . Unfortunately, there is very limited research addressing the prevalence and characteristics of an underweight Vietnamese population. Additionally, the BMI - criteria of the WHO are not specific enough to define what has to be considered as underweight in Asian people. Many Asian people tend to have a smaller body mass index compared to Western people and probably need a different set of criteria for the measure of body mass. The WHO has a recommendation for a BMI classification in Asians , but that only accounts for the differentiation between being overweight and obese.
A previous survey on participants in Ho Chi Minh City showed an increase in the number of overweight females. It found that 9.7% of females between the ages of 15 and 49 were overweight . Additionally, the prevalence of overweight females between the ages of 20 and 29 in Ho Chi Minh City was 11.3% . Another national survey showed that 2.5% of females between the ages of 18 and 34 were overweight . A survey from Hanoi in 2004 showed that 18.1% of females between the ages 25 and 34 were overweight . However, the result of the current study found only 1.5% as being overweight. Even if using the BMI- criteria for Asians, the percentages of overweight and obese females in the current study was 3.4% and 0.5%, respectively.
Hanoi and Ho Chi Minh City are the two largest cities in Vietnam and have populations of 6,936,900 and 7,818,200, respectively . Cuong et al.  reported that being overweight is associated with higher economic status in Ho Chi Minh City. This was especially true for males between the ages of 40 and 49 . The prevalence of overweight males in Vietnam might be attributed to being rich and successful, as weight increases with socio economic status and higher income, but these factors appear to be less relevant for women in Vietnam . The fact that only young female university students participated in the current study could explain why the rate of being overweight was lower as compared to findings from previous studies.
Disordered eating behaviors
48.8% of the participants reported two or more yes-responses on the SCOFF. According to Morgan et al.  this indicates that 48.8% of the Vietnamese participants have a very high possibility of having eating disorder symptoms. In the female group from a previous pilot study in Vietnamese high school students a similar percentage of 42.6% showed more than 2 yes-reponses . One particularly interesting result is that 49.8% of the participants answered ‘yes’ to the SCOFF question number 2 (Do you worry that you have lost control over how much you eat?). This result is the same as the result in the previous pilot study , where most of the female high school students answered ‘yes’ to question number 2. The SCOFF question number 3 (Have you recently lost more than one stone in a 3-month period?) received the fewest ‘yes’ answers in both studies. The pilot study  and the current study only found a very low percentage of obese participants. The rate of overweight participants was 1.6% and 1.5%, respectively. These similar results from two Vietnam samples indicate it might be possible that despite a low body mass index many young females in Vietnam worry about losing control of their eating behaviors. This indicates that there might be a potential risk for young females in Vietnam of developing disordered eating behaviors.
However, the relationship between the SCOFF score and the EDI-2 scales showed a significant negative correlation. Furthermore, there was a slightly negative correlation between the SCOFF and the BMI. Regarding reliability, according to Schmitt , a Cronbach’s alpha of 0.60 or 0.70 indicates an acceptable reliability, and 0.70 or higher values indicate a good reliability. Cronbach’s alpha of the SCOFF showed an insufficient reliability of 0.28 in the current study. The SCOFF questionnaire has been validated in the US and in the UK and in these countries showed good validity and reliability as a screening instrument . The SCOFF questionnaire has also been used as a screening test for children and adolescents in Germany, and it showed good validity as well . In addition, the SCOFF in the French version showed good accuracy and reliability for the detection of women with EDs in the high-risk French student population . In Asian cultures, the SCOFF score showed a positive relationship with the global score of the Eating Disorder Examination-Questionnaire and showed acceptable psychometric properties in Hong Kong secondary school students . However, it has been suggested that translated versions need to be amended to address cultural issues . Crosby et al.  mentioned that questions such as ‘do you make yourself sick’ may have different meanings outside of the UK. Furthermore, the Korean SCOFF questionnaires were inappropriate for improving the screening of eating disorders due to low internal consistency and reliability in the study by Jung et al. . In summary, the SCOFF has shown inconsistent reliability in diverse cultural groups. The insufficient reliability and the lack of a significant relationship between the SCOFF and the EDI-2 in the current study also shows that there is a need for further studies using the SCOFF questionnaire in different samples and adapt it according to different cultural contexts.
Cronbach’s alpha of the EDI-2 indicated a good reliability with 0.85 in the current study. The subscales drive for thinness and body dissatisfaction of the EDI-2 showed a positive and significant relation to the BMI. In particular, the underweight group showed significantly lower scores on these two scales compared to normal weight and overweight individuals. This means that Vietnamese female students are dissatisfied with their body and feel a drive to be thin when they consider themselves to be overweight. There is no cut-off score for the EDI-2, but higher scores can be assumed to be related to a greater possibility of having disordered eating behaviors. Therefore, it is possible that the normal and overweight groups of young female Vietnamese have difficulty with drive for thinness or body dissatisfaction. As mentioned before, the ideal of thinness as seen through mass media products from Western cultures might be influencing this development in young female students in Vietnam.
Some further limitations of the current study need to be mentioned: The sample included only female students in the capital city in Vietnam. In addition, the translated questionnaires were self-report instruments and have not been validated in Vietnam yet. Furthermore, there is no information about dieting behavior or traditional eating behavior in Vietnam that can help to better understand the results.