The proportion of underweight women among Japan’s young female population has remained at around 20% for years, standing in sharp contrast to the global focus on rising obesity rates.

OSAKA, JAPAN (MERXWIRE) –“Being a little thinner looks better” is a phrase commonly heard in everyday conversation in Japan. However, as this notion becomes widely accepted, body-weight issues have quietly shifted toward another extreme. Recent health surveys show that the proportion of underweight young women in Japan has remained consistently high, forming a clear contrast with the global trend toward obesity.

Data from Japan’s National Health and Nutrition Survey, released by the Ministry of Health, Labour and Welfare, indicate that while the country’s overall obesity rate remains among the lowest internationally, approximately 20% of women aged 20 to 29 fall below the healthy weight threshold (BMI < 18.5). This figure has shown slight improvement over many years, suggesting a structural issue rather than a short-term change in lifestyle habits.

Medical groups warn that being underweight is not merely a matter of appearance. In recent years, Japanese medical associations have pointed out that prolonged low body weight is closely associated with menstrual irregularities, reduced bone density, anaemia, and increased risks related to future pregnancy. These effects are particularly pronounced among women of childbearing age and may extend into midlife and older age.

Experts note that societal expectations surrounding body shape in Japan differ from those in many other countries. Compared with an emphasis on avoiding obesity, younger generations in Japan more commonly face subtle pressure to maintain thinness. Reports indicate that even women who already meet the medical definition of underweight may still perceive themselves as “not thin enough,” highlighting a gap between body image perceptions and clinical health standards.

At a time when global health discussions continue to focus heavily on weight loss and sugar reduction, body weight alone does not necessarily represent the endpoint of health. When thinness becomes the sole benchmark, early signs of physical imbalance are often overlooked. Specialists observe that fostering broader recognition of the importance of maintaining an appropriate body weight—rather than pursuing thinness alone—remains a key challenge in addressing long-term health risks.