A large part of research using questionnaires for female university students relies on self-reported body mass, height, and body mass index (BMI) data; however, the validity of these data in this population group is unknown. Therefore, the aim of the present study is to examine the validity of self-reported body mass, height, and BMI in female students. Female students of biomedical sciences (n = 93, age 21.8 ± 4.7 years, height 1.63 ± 0.06 m, weight 60.5 ± 11.9 kg, and BMI 22.7 ± 3.8 kg/m²) completed the short version of the International Physical Activity Questionnaire and were tested for anthropometric characteristics at three different times of the day (12-2 p.m., n = 36; 2-4 p.m., n = 20; 4-6 p.m., n = 37). Participants over-reported height (+0.01 ± 0.02 m, +0.9 ± 1.2%, Cohen's d = 0.22) and under-reported weight (-0.8 ± 2.1 kg, -1.2 ± 3.6%, d = -0.07) and BMI (-0.7 ± 1.0 kg/m², -2.9 ± 4.2%, d = -0.19) (p < 0.001). A moderate main effect of time of day on %Δweight (p = 0.017, η² = 0.086) and %ΔBMI (p = 0.045, η² = 0.067), but not on %Δheight (p = 0.952, η² = 0.001), was observed, where the group tested at 4-6 p.m. under-reported weight and BMI more than the 2-4 p.m. group. The weekly metabolic equivalent (MET) × min did not correlate with %Δheight (r = 0.06, p = 0.657), but its correlations with %Δweight (r = -0.27, p = 0.051) and %ΔBMI (r = -0.238, p = 0.089) reached statistical significance. Participants in the early follicular phase reported BMI more accurately (p = 0.084, d = 0.68) than those in the mid-luteal phase. In conclusion, female students over-reported height and under-reported weight and BMI. Under-reporting weight and BMI is influenced by time of day and menstrual cycle phase. These findings should be considered by health professionals and researchers when administering questionnaires to female students.
Keywords: MET; anthropometry; questionnaire; survey; vigorous exercise.