Relationship of masked obesity to self-reported lifestyle habits, ideal body image, and anthropometric measures in Japanese university students: A cross-sectional study

INTRODUCTION: Masked obesity (MO) is defined as a normal body mass index (BMI) with a high body fat percentage (%BF), and is associated with the onset of lifestyle-related diseases. However, little is known about the current status of MO. Therefore, we investigated the relationship of MO to physical characteristics and lifestyle habits among Japanese university students. METHODS: Between 2011 and 2019, we conducted a survey of 10,168 males and 4,954 females with BMI within the normal range (18.5 ≤ BMI < 25 kg/m(2)). MO was defined as %BF ≥ 20% in males and %BF ≥ 30% in females. Students completed a questionnaire containing items about lifestyle habits. Systolic and diastolic blood pressures were measured, and hypertension was defined as systolic above 140 mmHg and/or diastolic blood pressure above 90 mmHg. A multivariate logistic regression analysis was performed to evaluate the relationships as follows: the relationship of masked obesity to self-reported lifestyle habits, ideal body image, and anthropometric measures; the relationship between hypertension and body indices. RESULTS: The proportion of students with MO in 2019 was 13.4% in males and 25.8% in females, and the proportion of females increased over time. MO was associated with desire for weight loss (odds ratio, 95% confidence interval: 1.76, 1.53–2.02), intake of five macronutrients (0.79, 0.67–0.93), rice and wheat intakes (1.22, 1.01–1.47), sleep duration of < 7hr (0.85, 0.74–0.98), and exercise habit (0.71, 0.63–0.81) in males; and with balanced diet intake (0.79, 0.64–0.99) and exercise habit (0.65, 0.51–0.82) in females. There was a significant association of MO with hypertension in males (1.29, 1.09–1.53). CONCLUSION: The percentage of female students with MO increased during the study period, and in males, MO may be a risk factor for hypertension. These results suggest that intervention for MO is needed in Japanese university students.