Body fat accumulation, distribution and metabolic activity are factors in the pathophysiology of obesity and type 2 diabetes (T2D). We investigated adipose blood flow, fatty acid uptake (FAU), and subcutaneous and visceral fat cellularity in obese patients with or without T2D. A total 23 morbidly obese (BMI 42 kg/m²) patients were studied before and 6 months after bariatric surgery; 15 nonobese subjects served as controls. Positron emission tomography was used to measure tissue FAU (with ¹⁸F-FTHA) and blood flow (with H₂¹⁵O); MRI was used for fat distribution, fat biopsy for adipocyte size. Obese subjects had subcutaneous hyperplasia and hypertrophy, and lower blood flow; when expressed per cell, flow was similar to controls. FAU into subcutaneous and visceral depots was increased in the obese; per unit tissue mass, however, FAU was similar to controls but reduced in skeletal muscle. Fatty acid fractional extraction in subcutaneous fat and muscle was only increased in obese patients with T2D. We conclude that surgery leads to metabolic improvement and reduces subcutaneous fat hyperplasia and hypertrophy; subcutaneous blood flow and FAU decrease in absolute terms and per cell while fractional FAU remains unchanged in T2D. In the obese, subcutaneous blood flow is a determinant of FAU and is coupled with cellularity; efficiency of FAU is enhanced in subcutaneous fat and muscle in T2D.