Brown adipose tissue detected by PET/CT imaging is associated with less central obesity

Purpose This retrospective review was performed to determine whether patients with brown adipose tissue (BAT) detected by fluorine-18-fluorodeoxyglucose (¹⁸F-FDG) PET/computed tomography (CT) imaging have less central obesity than BMI-matched control patients without detectable BAT. Patients and methods Thirty-seven adult oncology patients with ¹⁸F-FDG BAT uptake were retrospectively identified from PET/CT studies from 2011 to 2013. The control cohort consisted of 74 adult oncology patients without detectable ¹⁸F-FDG BAT uptake matched for BMI/sex/season. Tissue fat content was estimated by CT density (Hounsfield units) with a subsequent noise removal step. Total fat and abdominal fat were calculated. An automated separation algorithm was utilized to determine the visceral fat and subcutaneous fat at the L4/L5 level. In addition, liver density was obtained from CT images. CT imaging was interpreted blinded to clinical information. Results There was no difference in total fat for the BAT cohort (34±15 l) compared with the controls (34±16 l) (P=0.96). The BAT cohort had lower abdominal fat to total fat ratio compared with the controls (0.28±0.05 vs. 0.31±0.08, respectively; P=0.01). The BAT cohort had a lower visceral fat/(visceral fat+subcutaneous fat) ratio compared with the controls (0.30±0.10 vs. 0.34±0.12, respectively; P=0.03). Patients with BAT had higher liver density, suggesting less liver fat, compared with the controls (51.3±7.5 vs. 47.1±7.0 HU, P=0.003). Conclusion The findings suggest that active BAT detected by ¹⁸F-FDG PET/CT is associated with less central obesity and liver fat. The presence of foci of BAT may be protective against features of the metabolic syndrome.