Politicians predict obesity epidemics bankrupting governments and mutating generations of people, parents Photoshop pictures of their toddlers, and the cosmetic-surgery industry grows by US$1 billion each year. In her new book the English psychotherapist Susie Orbach calls for a rethink of how we relate to our bodies. Western anxiety about obesity, she argues, both masks and legitimises a more pressing and widespread epidemic: "body dis-ease".

According to Orbach, the body has moved to the centre of our search for contentment and personal identity. Psychoanalysis is unable to understand or treat this explosion in body anxiety, because it has yet to acknowledge that the body has become - for women and for men - as complex, important and fraught as was sexuality in Freud's time.

The root of individuals' struggles with body image is not vanity, Orbach says, but a crisis in understanding what bodies are for. In contemporary society our bodies are no longer the result of physical work; rather, they are the purpose of it. And as the world has settled into its post-industrial swivel chair, the emphasis on exhibiting bodies that seem capable of intense physical activity has increased.

Bodies is a consistently illuminating book, and one of its most distinctive arguments is that democratisation has led to the canonisation of choice in all things, bodies in particular. We now choose whether or not to be flat-chested, to be impotent, to appear to age. For every flaw there is a medical solution - more often than not, one that supports the US$450 billion-a-year global beauty industry.

The distinction between fantasy and aspiration has collapsed, Orbach contends. Where once the bodies of great beauties and athletes were simply admired, now they are copied. Failure to replicate the ideal form suggests not only a person's lack of willpower, but an unwillingness to liberate themselves from their ethnic and class background and declare their membership of the new world order.

A sense of urgency runs through Bodies, but it is urgency without hyperbole. The book is engaging and convincing - both as a chronicle and a condemnation of our culture - and it may ultimately rival the three-decade-old Fat Is a Feminist Issue as Orbach's most influential work. Her aim is to start a debate about the point of the human body, and she is successful.