Sex And Age-related Differences In Perceived, Desired And Measured Percent Body Fat

Abstract

PURPOSE: Body image distortion can lead to psychological stress, disordered eating, and mental and physical disease. In order to begin to assess body image distortion we compared perceived, desired, and measured percent body fat in male vs female and younger vs older individuals. In addition, we assessed the acute stress response to body composition measurement in these various populations. METHODS: Body fat percentage of 15 younger (Y) (mean age of 19 years) and 16 older (O) (mean age of 39 years) male (n=5 younger, 4 older) and female (n=10 younger, 12 older) individuals was assessed with the BodPod Body Composition Tracking System. Height was measured using a wall-mounted stadiometer and weight in minimal workout clothes was recorded from a medical grade digital scale. Subjects indicated their perception of body fat as well as their desired body fat using a somatomorphic matrix which is a bi-axial instrument for measuring body image in men and women. Salivary cortisol was measured via competitive ELISA. Heart rate was assessed via hand pulse oximetry and blood pressure was measured using a sphygmomanometer and stethoscope. RESULTS: The mean percent body fat of males (15.2 +/- 6.1%) was significantly lower than that of females (28.4 +/- 6.4%) (p<.0001), although no difference was observed in the Y vs the O populations overall and no sex × age interaction was found. Both Y and O females perceived their body fat to be slightly lower (5%) than measured body fat and desired their body fat to be significantly lower (12%) than measured (p<.05). Younger and older male subjects demonstrated the opposite result and a significant interaction (measured, perceived, desired vs sex) was observed (p=.0002). Both Y and O male populations perceived their body fat to be slightly higher (5%) than measured body fat and desired their body fat to be significantly higher (4%) than measured (p<.05). No differences were observed in subjects' heart rate or blood pressure response to body fat measurement although a slight trend (p=.08) suggesting male subjects had slightly elevated cortisol levels compared to women subjects was observed. CONCLUSIONS: Sex-related, but not age-related, differences in perceived, desired and measured percent body fat were observed. Individuals did not appear to have an acute stress response to having their body fat measured.