According to the study, men looking at a curvaceous figure activate the part of the brain associated with feelings of reward.
Scientists say their findings make sense of the view that curvier women, such as Jennifer Lopez and Beyoncé Knowles, are sexually appealing.
Researchers used a sample of 14 men with an average age of 25 and showed them pictures of the posteriors of seven women.
They then carried out cosmetic surgery on the women, redistributing fat from their waists to the backsides but not changing their overall weight.
Brain scans of the men revealed that looking at the women after surgery activated parts of the brain linked with rewards, including regions associated with responses to drugs and alcohol.
Researcher Steven Platek, an evolutionary cognitive neuroscientist at Georgia Gwinnett College, in Georgia, USA, said: "There's more to it than buying magazines.
"These findings could help further our understanding pornography addiction and related disorders, such as erectile dysfunction in the absence of pornography.
"The findings could also lend to the scientific inquiry about sexual infidelity."
The scientists also found that changes in a woman's body-mass index (BMI) only affected brain areas linked to simple visual appreciation of size and shape.
Mr Platek said this may be evidence that body fat influences judgments of female beauty due more to society's norms than the way the brain is wired.
