Status of Normal Weight Obesity Among Japanese Women Under 40 Years Old

Objective : This study examined the prevalence of and factors affecting normal weight obesity (NWO) among women aged under 40 years old. NWO was having a normal BMI but a high body-fat percentage (BFP). Materials and Methods : We recruited 399 participants aged 18­39 during a health checkup and surveyed them about lifestyle patterns, height, weight, body composition, and girth and visceral fat area. Participants were divided into three. Those with a BMI of <25 and a BFP of <30 were classified as non-obese, a BMI of <25 and a BFP of ≥ 30 as NWO, a BMI of ≥ 25 and a BFP of ≥ 30 as obese. The analysis was conducted on NWO (97) and non-obese (262) groups. Results : NWO prevalence ranged from 20% to 30% across the three age groups. NWO participants had lower values for segmental lean body mass, particularly in lower limb, and higher values for abdominal girth and visceral fat area. Among participants aged 30­39, those with NWO had higher values for triglycerides and LDL cholesterol and lower values for HDL cholesterol. Regarding lifestyle factors, among those aged 30­39, NWO was associated with past weight fluctuation, respectively. In the latter age group, a gain of more than 10 kg since the age of 20 was associated with a 13-fold increase in the odds for NWO. Conclusions : Results suggest that for women under 40 years, detecting NWO early and guidance on effective lifestyle and exercise are necessary.