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Soaring obesity levels may trigger infertility crisis

28 August 2007
Appeared in BioNews 422

A Lancet report has warned that the soaring levels of obesity in the western world will lead to a major infertility crisis in women. Commenting on the findings, Bill Ledger, Professor of Obstetrics at the University of Sheffield, warned that in the next decade the number of women seeking infertility treatment could double, to one in five. Mr Ledger said that this problem could be helped if women lost weight before seeking infertility treatment.

The study focused on polycystic ovary syndrome (PCOS), which affects one in 15 women worldwide. One of the symptoms of PCOS is infertility, and the syndrome is exacerbated by obesity. The lead author of the study, Robert Norman from the University of Adelaide, stated 'it's argued that obesity will cause a crisis in infertility and I agree'.

Meanwhile, PhD student Cadence Minge, from the Adelaide University Research Centre for Reproductive Health, has scientifically linked obesity with infertility for the first time, by showing that eggs from obese mice do not develop into healthy embryos.

Ms Minge's study centred on female mice that were fed a high-fat diet, making them insulin-resistant and pre-diabetic. The mice eggs were harvested and grown in vitro, but did not develop into healthy embryos. Ms Minge commented that 'consuming a diet high in fat causes damage to eggs stored in female ovaries. As a result, when fertilised these eggs are not able to undergo normal, healthy development into embryos'.

A protein called PPAR gamma, which supports and nourishes the eggs, could be important in attempts to reverse infertility caused by obesity. Ms Minge also discovered that targeting the protein with the anti-diabetic drug rosiglitazone could reverse the damage to eggs caused by poor diet. Ms Minge explained that 'the drug enables us to switch on the protein, thereby changing the way in which the ovaries sense and respond to fats. Embryo development rates are restored, and the cellular differentiation of the early embryo is improved. In the long-term these improvements can result in increased birth weight and fetal survival'.

However, Ms Minge has warned that the drug could not be viewed as a 'quick fix'. The effects of rosiglitazone have only been seen in mice and that the drug itself has harmful side effects. Ms Minge emphasised the key role of weight loss in restoring fertility, and said that even a weight loss of five to 10 kilos would be enough to trigger ovulation in obese women who had ceased to ovulate.

Adult obesity levels have increased four-fold over the last 25 years, with two thirds of adults deemed overweight. Professor Ledger stated that obesity was a key factor in predictions that the number of couples seeking infertility treatments would double over the next 10 years. The incidence of PCOS in women is also expected to rise from 7 per cent to 10 per cent in the next decade. Professor Ledger said that while it was a common problem, it was most important to tackle the obesity levels. He said 'it's a problem that needs to be dealt with in lifestyle changes rather than through surgery. Losing weight will help women with PCOS get pregnant'.

SOURCES & REFERENCES
Body weight and infertility linked
The Age |  24 August 2007
'Fat Eggs' Causes Infertility In Obese Women
ScienceDaily |  27 August 2007
Infertility crisis looms in the west as obesity levels soar
The Guardian |  24 August 2007
Report links obesity with infertility
ScienceDaily |  24 August 2007
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