Foxp3+CD4+ regulatory T (T-reg) cells are a key population in controlling the immune response. Recently, their roles have been expanded to broader, non-immune, contexts, in particular the metabolic consequences downstream of obesity-induced inflammation, e.g. type-2 diabetes and cardiovascular disease. This review highlights the major innate and adaptive immune cell subsets contributing to adipose-tissue inflammation, the key role played by fat-resident T-regs, and the potential of T-reg-based therapies for treatment of the metabolic syndrome. (C) 2011 Elsevier Ltd. All rights reserved.