D. B. Stefan and D. A. Gilbert, "Longitudinal Statistical Analysis of Weight, Volume, Surface Area and Circumferential Measurements for a Female Bariatric Population", in Proc. of 6th Int. Conf. on 3D Body Scanning Technologies, Lugano, Switzerland, 2015, pp. 68-84, doi:10.15221/15.068.
Longitudinal Statistical Analysis of Weight, Volume, Surface Area and Circumferential Measurements for a Female Bariatric Population
David B. STEFAN 1, David A. GILBERT 2
1 Novaptus Systems Inc., Chesapeake, VA, USA;
2 The Hague Plastic and Cosmetic Surgery Center, Norfolk, VA, USA
Background. It is generally well known that morbidly obese individuals undergoing a gastric bypass or sleeve procedure will lose 75% of their excess weight about 1 year after their surgical procedure. What is not known is the relationship, if any, between weight loss and physical changes to the individual's body shape and their measurements, including volume and surface area as they undergo this dramatic transition. A statistical analysis of longitudinal data from a de-identified and aggregated female bariatric population was performed that compared weight and anthropometric data collected from 3D booth scanners pre-operatively to such data collected post-operatively at 3, 6 and 12 months. Comparisons were made between weight loss, volume loss, surface area loss and circumferential measurement changes and a set of descriptive statistics was produced for each time interval.
Methods. Aggregated anthropometric data has been collected over the past seven years from sites that utilized various 3D booth scanners to document the physical dimensions of pre-operative bariatric patients, and to track changes to their physical measurements on a periodic basis after bariatric surgery. Data collected included weight, height and anthropometric information generated by a measurement extraction profile (MEP) applied to the pre-operative scan image and subsequent periodic scan image for each individual. This provided a multidimensional set of measurements that could be compared longitudinally to the weight recorded at each scan instance. For analysis purposes, a set of 100 female individuals were randomly selected from this collection of de-identified data. Averages and standard deviations were developed for each scan interval and a set of summary statistics comparing the preoperative weight and anthropometric data to the final, 12 month weight and anthropometric data was produced.
Results. After 3 months the female population lost an average of 50 pounds, torso volume of 15,200 cc and torso surface area of 878 sq. cm. However there was a wide standard deviation during this period. The average waist measurement reduced by 5.8 inches and the average hips measurement reduced by 5.9 inches. The waist/hips ratio was statistically unchanged, as were each subject's relative shape indicators. After 6 months standard deviations between volume and surface area and weight began to tighten, indicating a correlation with volume and surface area loss with excess weight loss. Finally, as the individuals began to tend toward 75% excess weight loss after a period of one year, volume loss and surface area loss began to converge with excess weight loss. Common circumferential measurements lost an average of 33% at the end of 1 year after surgical weight loss.
Conclusion. Massive weight loss after surgery results in significant changes in body appearance. Previous longitudinal monitoring consisted mainly of recording changes in weight and circumferential measurements. This doesn't tell the whole weight loss story. Multidimensional data provided by 3D body scanning allows monitoring changes to volume and surface area. The relationship between weight, excess weight loss, circumferential, linear and volume and surface area can now be simultaneously examined. This adds unique insight as to where weight loss is occurring as the body undergoes dramatic changes.
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