Fat-adapted horses have been found to have faster times on the track as well as longer run times to fatigue and higher peak plasma lactate concentrations. Brown adipose tissue is distinct from white adipose tissue in its ability to expend energy and generate heat rather than as a lipid storage unit. Until recently it was thought that brown adipose tissue occurred only in mammalian infants but it is now thought that the metabolically active mitochondria-rich tissue may be retained in adults and derives from a common precursor cell for muscle. The incidence of brown adipose tissue in young horses and its persistence in adult horses, to our knowledge, have not been reported. Positive selection for genomic regions Pimozide containing genes such as ADHFE1 that preferentially functions in highly metabolic tissues including brown adipose tissue, as well as two of the key determinants of brown fat cell fate, BMP7 and RB1, and their receptors and signalling molecules, raises the intriguing question of whether Thoroughbred skeletal muscle retains brown fat-like properties, thus providing a selective advantage. The retention of brown fat into adulthood has been suggested as a mechanism to combat obesity and experimental increases in brown adipose tissue in rodents has been associated with a lean healthy phenotype. The oxidation of fatty acids is highly efficient in the generation of ATP and is controlled by the expression of PDK4 in skeletal muscle during and after exercise. Equine PDK4 is located in the genomic region that had the highest inter-population differentiation as well as a highly significant deviation from neutrality in the Ewens-Watterson test and is therefore one of the strongest candidates for selection for exercise Chloroquine Phosphate adaptation. The location of the ADHFE1 and ACSS1 genes in two of the strongest selected regions as well as a 2.2-fold overrepresentation of lipid transport genes and an abundance of genes with specific lipid metabolism function among positively selected genomic regions suggests that Thoroughbreds have been selected for aerobic energy production increasing flux through fatty acid oxidation and electron transport. High concentrations of circulating fatty acids have a disruptive effect on insulin signalling pathways causing insulin resistance and the manifestation of T2DM in humans. It has been reported that Thoroughbreds have an enhanced delivery of fat and glucose into skeletal muscle and accumulate less fat than other horse breeds when fed the same diet, which together may contribute to the naturally lean athletic phenotype for which they are renowned. The presence of genes that suggest a preference for the oxidation of fatty acids for energy production as well as insulin-mediated molecular signalling genes in the key selected genomic regions in a population that has been strongly selected for exquisite adaptations to exercise strongly supports the role of exercise in the prevention of obesity and the protection against T2DM. While rodent models for obesity and diabetes are well established, here we propose Thoroughbred as a novel in vivo large animal model that may contribute to further insights into the complex molecular interactions that serve to protect against obesity and related pathological phenotypes that are influenced by exercise. As modern therapies allow improved peripheral control of primary and metastatic disease, such as trastuzumab for metastatic breast cancer, the incidence of brain metastasis appears to be paradoxically increasing.