Background: Methods that facilitate muscle quality measurement may improve the diagnosis of sarcopenia. Current research has focused on the phase angle (PhA) obtained through bioelectrical impedance analysis (BIA) as an indicator of cellular health, particularly cell membrane integrity and cell function. The current study therefore aimed to evaluate the relationship between the PhA and muscle quality and muscle‐related parameters and to determine factors associated with the PhA. Moreover, we attempted to determine the cut‐off value of PhA for predicting sarcopenia.Methods: First‐year university students (830 male students, 18.5 ± 0.6 years old; 422 female students, 18.3 ± 0.5 years old) and community‐dwelling elderly individuals (70 male individuals, 74.4 ± 5.5 years old; 97 female individuals, 73.1 ± 6.4 years old) were included. PhA and other body composition data were measured using BIA, while muscle quality was calculated by dividing handgrip strength by upper limbs muscle mass. The relationship between PhA and the aforementioned parameters were then analysed, after which the cut‐off value of PhA for predicting sarcopenia was examined.Results: Multiple linear regression analysis revealed that age, skeletal muscle mass index (SMI), and muscle quality were independently associated with PhA in both sexes [male (age: standardized regression coefficient (β) = −0.43, P < 0.001, SMI: β = 0.61, P < 0.001, muscle quality: β = 0.13, P < 0.001) and female (age: β = −0.56, P < 0.001, SMI: β = 0.52, P < 0.001, muscle quality: β = 0.09, P = 0.007)]. Participants with sarcopenia had a significantly lower PhA compared with those without it (sarcopenia vs. non‐sarcopenia: young male participants, 5.51 ± 0.41° vs. 6.25 ± 0.50°, P < 0.001; young female participants, 4.88 ± 0.16° vs. 5.37 ± 0.44°, P = 0.005; elderly female participants: 4.14 ± 0.29° vs. 4.63 ± 0.42°, P = 0.009). Although no significant findings were observed in elderly male participants, the same tendency was noted. Receiver operating characteristic (ROC) curve analysis indicated that PhA had good predictive ability for sarcopenia in young male, elderly male, young female, and elderly female participants (area under the ROC curve of 0.882, 0.838, 0.865, and 0.850, with cut‐off PhA values of 5.95°, 5.04°, 5.02°, and 4.20° for predicting sarcopenia, respectively).Conclusions: The PhA reflected muscle quality and exhibited good accuracy in detecting sarcopenia, suggesting its utility as an index for easily measuring muscle quality, which could improve the diagnosis of sarcopenia.

Recently, the high prevalence of young Japanese individuals who are underweight has received attention because of the potential risk for sarcopenia. The aim of this study was to examine the prevalence and characteristics of sarcopenia in Japanese youth. In this cross-sectional study, we measured skeletal muscle mass using a multifrequency bioelectrical impedance analysis device and handgrip strength (HGS) and administered questionnaires on dietary habits and physical activity in 1264 first-year university students ages 18 to 20 y (838 men and 426 women). Sarcopenia was confirmed based on the presence of both low skeletal muscle mass and weak muscle strength. In all, 145 men (17%) and 69 women (16%) were diagnosed as underweight. Sarcopenia was diagnosed in 8 men (1%) and 5 women (1%). There was a significantly higher prevalence of low skeletal muscle mass index (SMI) and/or weak HGS in underweight individuals than in those in other body mass index (BMI) ranges. The multivariate analyses indicated that SMI and HGS were significantly associated with BMI in both sexes. Furthermore, after adjusting for BMI, both SMI and HGS were significantly associated with physical activity in men, and SMI was significantly associated with energy intake in women. First-year university students showed a high incidence of being underweight with low SMI and/or weak HGS, but the prevalence of sarcopenia was low in both sexes. There may be sex differences in factors related to muscle mass and strength, but further research is needed to clarify this.

Background/Objectives: To promote salt reduction before health problems arise, it is important to understand factors associated with reduced-salt product purchasing among consumers with low interest in such products. This study examined psychological determinants of intention to purchase reduced-salt products among Japanese adults who were not actively purchasing them. Methods: An exploratory sequential mixed-methods design was used, including qualitative interviews followed by a cross-sectional web-based survey of 800 men and women aged 18–59 years in Japan. Participants were categorized into precontemplation and contemplation stages based on the transtheoretical model. Associations between purchase intention and three Integrated Behavioral Model categories—attitude, perceived norm, and personal agency—were examined. Percentage-to-gain values were calculated for each belief item. Results: All three category scores were significantly associated with purchase intention, with attitude showing the strongest association (OR = 12.56, 95% CI: 6.93–22.79). In stratified analysis, attitude showed a stronger association in the precontemplation stage (OR = 18.40, 95% CI: 8.51–39.78), whereas no category score was significantly associated with purchase intention in the contemplation stage. In the precontemplation stage, relatively high percentage-to-gain values were observed for holistic wellness-oriented beliefs and product availability in usual supermarkets. Conclusions: Attitude was most strongly associated with intention to purchase reduced-salt products, particularly in the precontemplation stage. Holistic wellness-oriented beliefs and product availability may represent promising targets for future communication or food environment interventions. These findings may provide a basis for future studies testing strategies to increase actual purchases of reduced-salt products and reduce salt intake.

Background Recently, the high prevalence of young Japanese people who are underweight has received attention because of its potential impact on healthy life expectancy. Sarcopenia, defined as the presence of low muscle mass and function, is often observed in the underweight. However, few reports have described the prevalence and characteristics of sarcopenia in youth. Methods In this cross-sectional study, we measured skeletal muscle mass using a multifrequency bioelectrical impedance analysis device and handgrip strength (HGS) and administered questionnaires on dietary habits and physical activity to 1,264 first-year university students aged 18-20 years (838 males and 426 females). Sarcopenia was diagnosed based on the presence of both low skeletal muscle mass (SMI) and weak HGS according to the Asian Working Group for Sarcopenia. Results A total of 145 males (17.3%) and 69 females (16.2%) were diagnosed as underweight. Low SMI was diagnosed in 75 males (8.9%) and 18 females (4.2%), and weak HGS was diagnosed in 28 males (3.3%) and 10 females (2.3%). Then, sarcopenia was diagnosed in 8 males (1.0%) and 5 females (1.2%). There was a significantly higher prevalence of low SMI and/or weak HGS in underweight individuals compared with individuals in the other BMI ranges. The multivariate analyses indicated that SMI and HGS were significantly associated with BMI in both sexes. Furthermore, after adjusting for BMI, both SMI and HGS were significantly associated with physical activity in males, and SMI was significantly associated with energy intake and frequency of breakfast intake in females. Conclusions First-year university students showed a high incidence of being underweight with low SMI and/or weak HGS, but the prevalence of sarcopenia was low in both sexes. BMI, energy intake, frequency of breakfast intake, and physical activity were independently associated with skeletal muscle mass and strength in youth.