Scientists at the Universities of Pittsburgh and California, Santa Barbara, found that women with large hips and small waists are cleverer than those with either "apple-shaped" or linear bodies.
The study, to be published in the journal Evolution and Human Behaviour, also discovered that curvaceous women give birth to more intelligent children because hip fat contains polyunsaturated fatty acids critical for the development of the fetus's brain.
The researchers believe that the results shed light on why many men find curvy women more alluring.
For the research, the team used data from a study of 16,000 women and girls, which collected details of their body measurements and their scores in cognitive tests.
They found that those women with a greater difference between the waist and hips scored considerably higher on the tests, as did their children.
The researchers say that the ideal ratio for an intelligent curvy woman lies between 0.6 and 0.7.
They suggest that the fat around fuller hips and thighs contains higher levels of omega3 fatty acids which are essential for the growth of the brain during pregnancy.
Although these theories anticipate confirmation, Paula Hall, a sexual and relationship psychologist with Relate, said: "Having research that proves you can be sexy and intelligent is really positive. It shows that curvy women may be better at things other than raising children and doing cooking and housework."
The team said that their findings may also explain why children born to teenage mothers do worse in cognitive tests - because their mothers may have had deficient stores of the best fatty acids.
"The cognitive development of their children is reduced, and their own cognitive development is impaired compared with those mothers with a later first birth," Times Online quoted the researchers, as saying.
The study noted, however, that children born to teenage girls with traditional hourglass figures seemed to be protected from this phenomenon and fared better in tests.
Several scientific studies have shown that men are "hard-wired" to find women with a greater waist-hip differential the most attractive. However, no one has yet been able to elucidate this, although theories include better fertility, better childbearing abilities and longer life expectancy.
Dr Harry Witchel, a senior lecturer in physiology at the Brighton and Sussex Medical School and a body language expert on the television programme Big Brother, said: "Until this point the only thing we have accepted is that they [curvy women] are at an advantage in contemporary western society. What these people are saying is that they also have an advantage biologically."