Women who pile on the kilograms after the menopause are also likely to become more anxious, research suggests. Their lack of oestrogen is believed to disrupt the body's ability to control weight.
The study said those worst affected had a higher chance of being nervous.
Researchers measured the waistlines of 5,580 women aged between 40 and 59, of whom more than half were post-menopausal. They were asked questions to gauge their anxiety levels.
Women with the most abdominal weight for their height were 13 % more likely to be anxious than those with the lowest ratio.
The study, published in the journal Menopause, looked at Latin-American women and suggested that oestrogen may protect against anxiety. The hormone is produced when a woman produces an egg every month. The researchers at the Peruvian University of Applied Sciences said women might also feel ashamed about weight gain: Feelings of sadness, shame and frustration would lead to a health concern that could generate more anxiety.'
Anxiety, which is linked to heart disease, diabetes and respiratory disorders, affects around one in 13 people.
Dr JoAnn Pinkerton, executive director of the North American Menopause Society, whose journal published the findings, said: Hormone changes may be involved in the development of both anxiety and abdominal obesity because of their roles in the brain as well as in fat distribution. This study provides valuable insights for healthcare providers treating middle-aged women, because it implies that waist-to-height ratio could be a good marker for evaluating patients for anxiety.'
It has long been thought that women pile on the pounds during middle age because of stress-eating' or snacking on comfort food. But the new findings suggest weight gain may come before anxiety, and not the other way around.
The authors of the Peruvian study said: A recommendation deriving from our study could be that obese women, identified using the weight to height ratio, could be subjected to a screening for anxiety symptoms.'
Questions they asked to gauge anxiety included Have you been a very nervous person?' and Have you felt calm and peaceful?'