Body composition, inflammation and thermogenesis in pathways to obesity and the metabolic syndrome: an overview.

According to the World Health Organization, overweight and obesity are defined as abnormal or excessive fat accumulation that presents a risk to health. What constitutes 'abnormal' fat accumulation in this definition is not specified, but this most likely represents a consensus term that encapsulates the importance of adipose tissue dysfunctions, rather than solely excess fat per se, in the pathogenesis of disease entities of the metabolic syndrome, particularly type 2 diabetes and cardiovascular diseases. Over the past decades, such abnormalities in fat accumulation have been linked to a pattern of fat distribution characterized by disproportionate fat deposition in the abdomen; to limits in the capacity of adipose tissue to expand resulting in the burden of fat storage being shifted to 'lean' tissues/organs as ectopic fat; and to the secretion (by both intrinsic and infiltrated cells within the adipose tissue mass) of a plethora of cytokines and other factors which via their autocrine, paracrine and/or endocrine actions underscore a state of chronic low-grade inflammation. These links have formed the basis of a multitude of adipocentric concepts that have stimulated basic and clinical research aimed at explaining differential susceptibilities to cardiometabolic diseases according to diet and lifestyle, birth weight and post-natal growth patterns, menopausal transition and the ageing process, race and ethnicity--often within the framework of hypotheses constructed around thrifty genotypes or thrifty phenotypes, and around overlapping molecular pathways implicated in metabolic inflammation, thermogenesis and body composition regulation. It is against this background of rapidly advancing research in metabolic health--fuelled as much by the search for early markers of cardiometabolic risks as by the search for 'druggable' molecular targets for treating obesity and its comorbidities--that fundamental concepts, controversies and novel research avenues relevant to the theme of 'Body composition, Inflammation and Thermogenesis in Pathways to Obesity and the Metabolic Syndrome' are addressed in this overview and the 10 review articles in this supplement reporting the proceedings of the 6th Fribourg Obesity Research Conference (FORC-2011).