Fifteen Thoroughbred geldings on an eight month weight gain study were used to evaluate 1) the effects of weight gain and diet on body area (neck, withers, shoulders, ribs, loin, tailhead) condition scores, and 2) the effects of weight gain, diet, and exercise on serum concentrations of tumor necrosis factor-α. The body condition scoring system developed in Quarter horse was slightly modified for use Thoroughbred geldings and involved developing prediction equations that utilized a smaller subset of the body areas. Horses at a BCS of 4 were found to be at a higher risk of inflammation that horses at a BCS of 7. The degree of inflammation was similar between horses fed either a high starch and sugar diet or high fiber and fat diet, indicated by similar TNF concentrations. Restricting daily exercise for two weeks was associated with increased inflammation.