Association between Normal Weight Obesity and Skeletal Muscle Mass Index in Female University Students with Past Exercise Habituation

This study investigated the relationship between normal weight obesity (NW-O) and skeletal muscle mass index (SMI) in 120 female university students who participated in sporting activities during junior and senior high school. The current physical activity level (PAL) was estimated by a factorial method using 24-h physical activity recall. The body mass index (BMI) of the participants ranged from 18.5 to 24.9 kg/m(2); their body fat (BF) was classified as NW-O if above the 75th percentile (28.9% BF), normal weight and lean (NW-L) if below the 25th percentile value (21.0%BF), and all others were normal weight (NW). PAL was significantly lower in NW-O than in NW-L. SMI was significantly lower in NW-O than in NW and NW-L, and 60% of NW-O had Low-SMI (<6.3 kg/m(2)). Although lower limb muscle mass was significantly lower in NW-O than in NW and NW-L, no significant differences were found in the upper limbs. These results suggest that the current PAL is associated with NW-O, and NW-O is associated with a lower SMI, even in young females with past exercise habits. Therefore, the prevention of NW-O in young females is important for the prevention of not only lifestyle-related diseases, but also future sarcopenia.