AbstractObjectiveWe 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).MethodsIn 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.ResultsAbdominal 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.ConclusionsAge 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.