Extracted from the Straits Times dated 27 May 2002



They still have periods and are unaware of any problem until they try - and fail - to get pregnant, warns a new book

LONDON - Millions of healthy young women are making themselves infertile by surviving on low-fat diets that silently 'switch off' their reproductive systems, according to a controversial new book.

Women who keep themselves just slightly underweight are most at risk.

'There is a close connection to fat and fertility. We can think of it as 'sex fat' because body fat provides the energy for reproduction,' Professor Rose Frisch, author of Female Fertility and the Body Fat Connection, was quoted as saying in the Observer newspaper.

'Many women who maintain the body shape made popular on catwalks throughout the world are completely infertile,' she said.

'These women can, however, continue having periods and not guess that a thing is wrong with them until they try - and fail - to fall pregnant.'

Prof Frisch, who is associate professor of population sciences emerita at the Harvard School of Public Health and a member of the research faculty of the Harvard Centre for Population and Development Studies, has spent 20 years researching the link between body fat and fertility.

'What I found most astonishing is that there is a razor-thin borderline where losing just 1.3 kg in weight can tip a normal-sized woman over into infertility without any outward sign at all that such an enormous event has taken place,' she said.

Her theory has been greeted with enthusiasm by other experts in the field, according to the Observer.

'This is one of the most simple and elegant theories in biology,' said Professor Robert Barbieri, the Kate Macy Ladd professor of obstetrics at Harvard Medical School.

'In women, body fat provides the over-arching control of the organs responsible for reproduction, and Frisch's findings will help us answer some of the most vital hitherto unanswered questions concerning fertility and women.'

Prof Frisch criticises the fear of fat shared by many women, pointing out that a young woman who is not overweight should have 16 kg of fat in her body while a woman who is well-nourished should be made up of 40 per cent fat.

A well-nourished adult man, by contrast, is only 30 per cent fat.

According to Prof Frisch, if low body fat switches off a woman's reproductive system for too long, there may come a point where it is too late to regain fertility by simply putting on weight.

Although doctors commonly claim that women need to have a body mass index, or BMI, of between 20 to 25 to be healthy, Prof Frisch's research enabled her to be more specific.

'If a woman has a body mass of 18 or 19, she will continue to have periods but will be infertile,' she said.

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<b>CALORIES FOR PREGNANCY</b>


A SUCCESSFUL pregnancy costs about 50,000 calories over and above normal metabolic requirements, while nursing, or lactating, costs about 500 to 1,000 calories a day.

If the body does not contain the necessary calories, the brain will simply switch off the body's ability to reproduce by gradually restricting the flow of a hormone called leptin.