Once a symbol of wealth, now a danger to health.

Obesity is a massive danger to health. It is the primary driver for the development of Type 2 Diabetes, promotes high blood pressure, increases the risk of heart disease, and is emerging as one of the bigger preventable causes of cancer.

Many healthcare professionals also consider obesity to be a disease in itself. As one researcher in Obesity Medicine has put it, "it shortens life, causes painful symptoms and other health complications, and puts people at risk for other diseases." And it is not only a problem here at home. According to the World Health Organization global statistics, in 2005 at least 400 million adults and 20 million children under the age of five were obese.

Obesity is not only a health risk. For thousands of years it has also acted as a powerful social and cultural symbol. But what it has symbolised has shifted remarkably over time. While in the past being fat could be seen as a symbol of health and well-being, it has been transformed into a sign of psychological, physical and even moral dissipation.

Some Egyptian art, such as a wall relief found at Karnak depicting a man with fleshy breasts and rolls of fat on the stomach, used obesity to indicate wealth and prosperity. This seems ironic to us now, at a time when obesity is seen as an index of poor lifestyle and low status. Much more recently, keeping a child very well-fed has been viewed by some as a sign that children are well looked after and nurtured by their parents. This myth is debunked in the 1967 film made by the British Medical Association, 'A Cruel Kindness'. Containing fascinating footage of 1960s domestic life and attitudes to food and eating, it argues that 'fatness begins at home' through overfeeding by 'well-meaning' mothers who think they are doing the right thing by treating their children to large - but ultimately unhealthy - meals.

On the other hand, there are many examples of how obesity has been used to express a wide variety of negative attributes. The sixteenth century French author Pierre Boistuau's 'Histoires prodigieuses' - a collection of tales of monsters and freaks of nature - includes the story of a king who was so fat that he used leeches to suck out his excess fat. The king was featured in a chapter on notorious gluttons and drunkards, suggesting the connection between obesity and moral degeneracy.

Boistuau's inclusion of obesity in his catalogue of freakishness is not unique. The spectacle of the unusually fat was commonplace in nineteenth and early twentieth century freakshows. One of the best known of these was Daniel Lambert, described in the Oxford Dictionary of National Biography as 'the most corpulent man of his time in England'. As the many portraits made of Lambert suggests, he was a celebrity in his lifetime and for decades after his death. Weighing over fifty stone by his mid-thirties, he began exhibiting himself in London where spectators would pay a shilling to see his prodigious proportions.

This voyeuristic interest in the freakishly different is suggested even where a genuine scientific aim exists, such as in Eadweard Muybridge's studies in human movement. His collotype print of an extremely obese woman walking was one series in Muybridge's enormous 11-volume work 'Animal Locomotion', published in 1887.

Seeing bodies of this size often prompts moral judgements about a lack of self-discipline or an abdication of individual responsibility. But is obesity something we can help, or is it something that happens to us? This is explored in a startling sculpture by John Isaacs, 'I Can Not Help the Way I Feel'. This work, which depicts a body that has been overrun by a sea of flesh, questions the relationships between obesity, control, and psychology. Obesity is used here as a visual metaphor for emotional fragility - the self being overrun by an uncontrollable torrent. The invisibility of the figure's head implies that when we look at an obese person we are so repelled by their size that we cease to see the individual at all. It may also represent the sense of personal shame often attached to obesity.

'Eat 22', a photographic work by Ellie Harrison also documents how far eating and self-control are intertwined. For a year and a day Harrison photographed herself at every meal, a powerful visual metaphor for society's obsession with food and consumption.