1 Department of Health, Kinesiology, and Applied Physiology, Concordia University, Montréal, Québec, Canada.
2 Metabolism, Obesity, and Nutrition Laboratory, School of Health, Concordia University, Montréal, Québec, Canada.
3 Centre de recherche - Axe maladies chroniques, Centre intégré universitaire de santé et de services sociaux du Nord-de-l'Ile de-Montréal, Hôpital du Sacré-Coeur de Montréal, Montréal, Québec, Canada.
4 Division of Geriatric Medicine, Department of Medicine, McGill University, McGill University Health Centre (MUHC) - Montréal General Hospital, Montréal, Québec, Canada.
5 Division of Endocrinology and Metabolism, Department of Medicine, McGill University, Royal Victoria Hospital, MUHC Glen Site, Montréal, Québec, Canada.
6 Division of Experimental Medicine, Department of Medicine, McGill University, MUHC Glen Site, Montréal, Québec, Canada.
7 Cardiovascular Health Across the Lifespan (CHAL) Program, Research Institute of the McGill University Health Centre (MUHC), Montréal, Québec, Canada.
8 Division of Internal Medicine, Department of Medicine, McGill University, Royal Victoria Hospital, MUHC Glen Site, Montréal, Québec, Canada.
9 Department of Sport, Physical Education, and Health, Faculty of Social Sciences, Hong Kong Baptist University, Kowloon Tong, China.

Objective: We aimed to examine the effect of age of obesity onset, sex, and their interaction on abdominal and femoral subcutaneous adipose tissue (SAT) morphology (degree of adipocyte hyperplasia or hypertrophy).

Methods: In this cross-sectional study, we isolated adipocytes via collagenase digestion from abdominal and femoral SAT biopsies taken from male and female adults with childhood-onset obesity (CO; n = 8 males, n = 16 females) or adult-onset obesity (AO; n = 8 males, n = 13 females). Regional body composition was measured with dual-energy x-ray absorptiometry and a single-slice abdominal computed tomography scan. Mean adipocyte size was measured in abdominal and femoral SAT and was used to quantify morphology in android and gynoid subcutaneous fat, respectively.

Results: Abdominal SAT morphology was more hyperplastic in females with CO than females with AO (p = 0.004) but did not differ between males with CO and males with AO (p = 0.996). Conversely, femoral SAT morphology was more hypertrophic in males and females with CO than those with AO.

Conclusions: Age of obesity onset appears to affect SAT morphology differently in the abdominal and femoral regions of male and female adults. Our findings challenge the notion that SAT is uniformly hyperplastic in CO and hypertrophic in AO.