Waist size and shape assessed by 3D photonic scanning

Abstract

Objective: To quantify waist girth at alternative locations using 3D photonic scanning and to identify the relationship between shape and size in a heterogeneous sample. Methods: Sixty-two male and 32 female healthy adults (aged 30.1 + 14.5 y) were assessed for stature, mass and 3D shape via photonic scanning, which enables the digital analysis of an individual’s body shape, avoiding postural and breathing artefacts which affect repeated measures using conventional anthropometry. Waist locations inferior to the 10th rib, and superior to the iliac crest, were identified as the ‘maximum’, ‘minimum’, ‘umbilicus’, and ‘maximum anterior extension’ via digital landmarking using system software. Sagittal and coronal diameters were measured at each waist. Girths were compared using repeated-measures ANCOVA with gender and age included, and Bonferroni adjustments made for multiple comparisons. Results: Across sites, waist girths differed by 4.9% in males and 11.7% in females. Girths showed differences at all four sites except maximum v maximum anterior extension (P = 0.061), (umbilicus v maximum P = 0.003; all other comparisons P < 0.0001). Waist girths were different between men and women ( P < 0.001), with a site-by-gender interaction (P < 0.001) and increased with age all four sites (all P < 0.001; β slopes 0.59 - 0.74 cm.yr-1). All pairwise comparisons of girth became different after excluding four men whose umbilicus fell slightly below the iliac crest. Shape (identified as sagittal : coronal diameter ratio) was highly correlated with body size at all sites. Conclusion:Waist girth exhibits significant variation according to site and is more variable in women than men. Waist increases with age and shape shows a progressive change with increasing body size.