When does "large" become "obese"? In more technical terms, at what point does an acceptable variation in bodyweight become a pathological condition? And how does an individual's lifestyle become subject to public and medical scrutiny? A stroll round any gallery offers a striking insight into these questions. Contemporary stars may prefer the lean, tense lines of a Mario Testino photograph, but well into the Enlightenment European elites favoured the ample, sensuous contours of Peter Lely and Peter Paul Rubens.