Body fat distribution, adipocyte size, and metabolic characteristics of nondiabetic adults.

CONTEXT: It is unclear whether adipocyte size or body fat distribution is most strongly linked to the metabolic complications of obesity. OBJECTIVE: Our objective was to test whether adipocyte size better predicts metabolic characteristics of obesity than body composition. DESIGN, PARTICIPANTS, AND SETTING: We analyzed the relationship between metabolic and anthropometric data collected from 432 largely Caucasian research volunteers (264 women) participating in studies conducted in the Mayo General Clinical Research Center between 1995 and 2008. MAIN OUTCOME MEASURES: Metabolic variables included fasting plasma glucose, insulin, and triglyceride concentrations. Anthropometric variables included body composition, fat distribution, and sc abdominal and femoral adipocyte size. RESULTS: Using both univariate and multivariate regression analysis, fasting triglyceride in both men and women was best predicted by computed tomography of visceral fat area. Fasting insulin concentrations were best predicted by sc abdominal fat area in women (r(2) = 0.40; P < 0.01) and body mass index in men (r(2) = 0.53; P < 0.0001); adipocyte size did not contribute independently. In men, fasting glucose concentrations were predicted by femoral adipocyte size (partial r(2) = 0.07; P = 0.002), body mass index (partial r(2) = 0.03; P = 0.07), and age (partial r(2) = 0.02; P = 0.06). In women, fasting glucose was predicted by abdominal sc fat area (partial r(2) = 0.12; P < 0.0001) and age (partial r(2) = 0.03; P = 0.01). CONCLUSIONS: Our hypothesis that adipocyte size is the best predictor of metabolic characteristics was not supported in this population. The alternative explanation is that fat mass and body fat distribution have more influence on metabolic responses than adipocyte size.

Subcutaneous adipocyte size and body fat distribution.

BACKGROUND: Both body fat distribution and adipocyte size are associated with metabolic abnormalities. OBJECTIVE: We defined the extent to which subcutaneous adipocyte size is related to regional fat mass and to the sizes of adipocytes in other subcutaneous depots independent of adiposity, age, and sex. DESIGN: Data collected from 188 women and 133 men who were 18-50 y old and who had a body mass index (in kg/m2) of 18 to 50 were analyzed. The mean size of isolated subcutaneous abdominal, femoral, and gluteal adipocytes was measured by direct microscopy or by automated analysis of digital images. Visceral fat area was measured with computed tomography. Dual-energy X-ray absorptiometry was used to calculate adiposity. RESULTS: Stepwise multiple regression analyses showed that abdominal adipocyte size was associated positively with visceral and subcutaneous abdominal fat areas and negatively with lower-body fat mass as a percentage of total-body fat, after control for sex and percentage body fat. Femoral adipocyte size was related to percentage body fat (P<0.0001), whereas gluteal adipocyte size was related to visceral fat area (P=0.002), which suggests that these 2 lower-body fat depots are distinct. Analyses of data from a subset of volunteers (n=99) for whom we had adipocyte size from all 3 depots showed that adipocyte size from 1 depot could be better predicted if adipocyte size from other depots were known. CONCLUSIONS: Abdominal adipocyte size is related to body fat distribution. Adipocyte size in a person seems to be globally regulated by factors independent of variations in body fat distribution.