Pear-shaped women who find slimming a challenge may end up "losing it" in other ways, research suggests.
A study shows that women who are wide at the hips are more likely to experience memory loss and mental decline late in life.
Scientists studied 8,745 women aged 65 to 79 who were given scores out of 100 after taking a mental test.
Although all the women were classified as "cognitively normal", the results revealed differences linked to weight and body shape.
Test scores dropped by a point for every one-point increase in body mass index (BMI), a standard measurement based on weight and height.
Being overweight was generally associated with reduced memory and brain function. But overweight pear-shaped women were more affected than "apples" with thick waists.
The American researchers suspect this is because of the type of fat deposited around the hips.
"Obesity is bad, but its effects are worse depending on where the fat is located," said study leader Diana Kerwin, from Northwestern University in Chicago.
The findings are published in the Journal of the American Geriatric Society.
Fat cells release immune system signalling molecules called cytokines that may affect the brain, scientists believe.
Different kinds of fat are known to release different cytokines that have various effects on blood fats, blood pressure and the way the body responds to insulin.
"We need to find out if one kind of fat is more detrimental than the other, and how it affects brain function," said Dr Kerwin. "The fat may contribute to the formation of plaques (brain deposits) associated with Alzheimer's disease or a restricted blood flow to the brain."
She added: "This study tells us if we have a woman in our office, and we know from her waist-to-hip ratio that she's carrying excess fat on her hips, we might be more aggressive with weight loss. We can't change where your fat is located, but having less of it is better."
British women are far more likely to have pear-shaped bodies than the hour-glass figure personified by Marilyn Monroe and Kate Winslet, fashion industry research has shown.
Rebecca Wood, chief executive of the Alzheimer's Research Trust, said: "The pear-shape is incredibly common, and while this study doesn't explain fully the link between body shape and brain function, it surely makes the case for watching the scales.
"There is little we can do about our natural body shape, but a lot we can do about our weight. With so much evidence of the dangers of obesity, we could all do well to consider sensible lifestyle changes to keep our weight in check."