In South Korea, the national health insurance system mandates that all citizens undergo regular health checkups every two years. During these checkups, doctors assess various health metrics, including Body Mass Index (BMI). If an individual's BMI indicates that they are overweight, doctors explicitly recommend weight loss and classify them as obese. This classification is due to South Korea's more stringent BMI standards compared to those of the United States.

South Korea's lower BMI standard does play a role in encouraging slimmer physiques among Korean women compared to those in the U.S. By setting the overweight and obesity thresholds lower, health guidelines in South Korea promote early attention to weight management, making it more common for individuals to adopt healthy habits around diet and exercise to stay within these guidelines.

BMI, or Body Mass Index, is a measure used to assess whether a person has a healthy body weight for a given height. It is calculated by dividing a person's weight in kilograms by the square of their height in meters. The formula is: BMI=weight(kg)/height(m)

Here are the general categories for BMI:

Underweight: BMI less than 18.5

Normal weight: BMI 18.5 to 24.9

Overweight: BMI 25 to 29.9

Obesity: BMI 30 or greater

In South Korea, the strong cultural value placed on slenderness and appearance reinforces this effect. The influence of media, beauty standards, and social pressure to maintain a slim figure means that many people, especially women, are mindful of staying within these stricter BMI categories. Public health initiatives also emphasize maintaining a lower weight, aligning with these cultural preferences to promote both health and the desired aesthetic.

By contrast, the U.S. has higher BMI thresholds and a somewhat more inclusive approach to body size, meaning people may feel less pressure to stay within a narrow weight range. Combined, these factors contribute to the cultural differences in body size and appearance between women in South Korea and the U.S.

In South Korea, BMI categories are adjusted downward to account for different average body compositions compared to Western populations. The World Health Organization (WHO) suggests that, for Korean populations, health risks like diabetes and hypertension may appear at a lower BMI than in Western populations. As a result, a BMI of 23 or higher is often considered "overweight" in South Korea, whereas in Western standards, the overweight threshold typically starts at 25. Obesity in South Korea begins at a BMI of 25, while the threshold for obesity in the U.S. is usually set at 30.

Let’s look at an example using the BMI classifications commonly used in South Korea and the U.S. Suppose we have a girl who is 160 cm (5'3") tall:

1. South Korea (BMI standard for obesity starts at 25): Weight threshold for obesity: BMI 25 × (1.6)^2 = 64 kg (141 lbs). In South Korea, this girl would be classified as obese if she weighs 64 kg (141 lbs) or more.

2. United States (BMI standard for obesity starts at 30): Weight threshold for obesity: BMI 30 × (1.6)^2 = 76.8 kg (169 lbs). In the U.S., this girl would be classified as obese if she weighs 76.8 kg (169 lbs) or more.

So, for a girl who is 160 cm (5'3") tall: In South Korea, a girl weighing 64 kg (141 lbs) would be considered obese. In the U.S., she would need to weigh 76.8 kg (169 lbs) to be classified as obese.

The BMI standards in South Korea do suggest different societal views on body size, beauty, and health compared to countries like the U.S., where thresholds are higher. In South Korea, there’s a strong cultural emphasis on slimness as part of the beauty ideal, often seen in media and advertising, which frequently showcase very thin body types as aspirational. This emphasis on slender physiques shapes beauty standards, and there's a high level of social consciousness around weight and appearance, especially for women. Consequently, the social acceptance of larger body sizes is generally lower, and wellness culture often stresses the importance of maintaining a slim figure.

Health considerations also influence these standards, as research suggests that some health risks, like diabetes and heart disease, may appear at lower BMIs for Asian populations. Thus, South Korean health authorities use lower BMI thresholds as a public health measure, aiming to encourage early prevention and weight management.

In contrast, although the U.S. still often values thinness, there is broader acceptance of diverse body types. Body positivity and inclusivity movements have gained momentum in the U.S., promoting acceptance of various body sizes and fostering a more flexible approach to beauty. This difference in standards reflects how social acceptance and cultural norms can shape BMI classifications and influence body image ideals across these societies.

As a result, both men and women in South Korea are highly motivated to lose weight if they are classified as overweight. The societal pressure to maintain a healthy weight is strong, and individuals often take proactive measures to achieve and maintain a slim physique. This cultural emphasis on health and fitness is reflected in the widespread efforts to manage weight and promote overall well-being.