Young girls are under enormous pressure to be slim. Many feminists often lament that women have achieved liberation in many spheres only to have become shackled to an idealised and unreachable body image.
As far as shape is concerned, research has focused on the ratio of waist to hips (WHR). A low WHR (a curvaceous body) supposedly represents the optimum fat distribution for high fertility. Which is why, say evolutionary psychologists, men find curvy women attractive. Studies in which men are asked to rate line drawings of women for attractiveness suggest that WHR is a more important predictor than what the scales show. They also suggest that men prefer women to have waists that are roughly two-thirds the measurement of their hips (36in hips, 24in waist).
So why do many men find stick-thin supermodels sexy? In a recent study, "Supermodels: stick insects or hourglasses?", published in The Lancet, psychologist Martin Tovee and colleagues from Newcastle University's department of psychology compiled a database of 300 fashion models, 300 glamour models, and 300 "normal" women. The fashion models were drawn from model agencies, the glamour models came from Playboy magazine, while the "normal" women were undergraduates and postgraduates with no clinical history of eating disorders. For comparison, they included 30 anorexic women and 30 bulimic women recruited from Newcastle City Health Trust's eating disorder service. They calculated each woman's body-mass index (BMI), waist-hip ratio, waist-bust ratio and bust-hip ratio. The BMI is calculated as weight in kilograms divided by height in metres squared (have a look on the internet to see what yours should be).
The key finding of Tovee's study is that the fashion models were on average 11cm taller than the normal women. They were significantly underweight on the basis of BMI, as were the glamour models, but were heavier than anorexic women. Both groups of models had a waist-hip ratio close to the optimum and, believe it or not, tended to have an hourglass figure. Indeed, fashion and glamour models had similar measurements, although glamour models are usually regarded as more curvaceous. The key difference may be height; supermodels appear a lot thinner simply because they are so tall.
So supermodels are both tall and curvaceous, and dieting will not make you look like a Vogue cover girl. The taller you are, the slimmer you look...
Dr Raj Persaud is Gresham professor for public understanding of psychiatry, and director of the Centre for Public Engagement, King's College London.
His latest book is The Motivated Mind (Bantam Press). Email: email@example.com