The 2020 Vietnam’s beauty contest has concluded, and Miss Đỗ Thị Hà has been crowned Miss Vietnam 2020 . The 19 yr old girl stands at a proud 175 cm tall, but her weight was only 55 kg. She and her fellow beauty contestants are classified as ‘underweight’.
I have over the years collected data pertaining to basic anthropometric parameters of Miss Vietnam titleholders. The data show that their height has increased over time. For instance, in 1988 (the first year of beauty contest in unified Vietnam) the winner was only 157 cm tall, but this had quickly increased to ~170 cm mark in the 1990s (Figure 1).
The average height of all Miss Vietnam winners was 170.6 cm. The average height of Vietnamese women aged between 18 and 35 was 155 cm (with standard deviation being 5.3 cm). Thus, the average height of Miss Vietnam was 2.85 standards deviation taller than their counterparts in the general population. The probability that a Vietnamese woman has a height of at least 170 cm is only 0.24%.
Is the height of Miss Vietnam titleholders different from that of Miss Universe titleholders? Well, according to wikipedia, the average height of Miss Universe was 172.7 cm, 2.1 cm taller than their Vietnamese counterparts. However, the difference was not statistically significant (P = 0.17 by t-test).
What about body mass index (BMI)? Miss Đỗ Thị Hà weighted 55 kg, and her BMI = 55 / (1.75²) = 18 kg/m². According to the World Health Organization, an adult individual with BMI < 18.5 is considered ‘underweight’ (undernutrition?). So, Miss Đỗ is classified as underweight.
However, she is not alone. My data show that among the 13 Miss Vietnam pageants (with complete data), 10 (or 77%) were underweight.
Still, the trend of underweight among beauty pageants is also observed in Miss Universe. Indeed, before 1980s, almost all Miss Universe titleholders had BMI above 18.5, but since 1990s their BMI was consistently lower than 18.5. This trend was opposite to that observed in the general population where BMI tended to increase with time.