Friday August 24 2007
The relationship between obesity and PCOS is complex
Levels of obesity in the western world are “soaring” and this may lead to an “infertility crisis” in women, The Guardian reported today. The newspaper continued by saying that couples seeking infertility treatment could double to one in five within the next 5 years, but also that the problem could be eased if women lost weight.
The story’s origin is a journal article on polycystic ovary syndrome (PCOS), a condition thought to affect about 1 in every 15 women. Women with PCOS have excess levels of male hormones (androgens), an irregular pattern of ovulation, and cysts on their ovaries. Because of these aspects of the condition, women with PCOS may experience difficulties in getting pregnant. According to the lead author of the article, obesity does not cause PCOS, however, the condition exacerbates it, making it more difficult to get pregnant.
The article does not address the levels of obesity in the general population, or the effects of obesity on fertility where PCOS is not a factor. While PCOS is a fairly common condition, the relationship between obesity and PCOS is complex and further research will be needed before it can be concluded that the obesity epidemic is causing an infertility crisis.
Where did the story come from?
Dr Robert Norman of University of Adelaide, Australia, and colleagues from Hopital Jeanne de Flandre, Lille, France, and Penn State College of Medicine, USA, have written this article. The article has been published in the peer-reviewed journal, The Lancet.
What kind of scientific study was this?
The authors have written an article based on current knowledge about the prevalence, diagnosis, clinical features and treatment of PCOS, based on published reports and research articles that have been identified through searches of electronic databases.
What were the results of the study?
The article discusses existing knowledge of the condition, including a discussion on recent changes in the classification of PCOS and how this will increase current estimates of how many women have the condition.
The report then runs through the individual hallmarks of PCOS, including increased male hormone levels, irregular ovulation or anovulation (no egg release from the ovaries) leading to menstrual problems; and finding of cysts on the ovaries with ultrasound.
In the part that is relevant to the newspaper story, the authors state that the causes and risk factors for PCOS are largely unknown, but both genetic and environmental factors have been suggested to play a role. If you are obese, the problems associated with PCOS are likely to be worse. The authors suggest that it may also worsen metabolic problems, such as control of blood sugar, and fertility problems in obese women. Obesity also “might promote” the development of symptomatic PCOS in women who are susceptible. i.e. if you are at risk of getting symptomatic PCOS, being obese will may make that risk more likely.
The authors also report figures from other review articles suggesting that even small amounts of weight loss can improve metabolic and reproductive fitness in women with PCOS.
What interpretations did the researchers draw from these results?
As discussed in the news report, the researchers conclude that “obesity has a substantial effect on the manifestation of polycystic ovary syndrome”. They say that excessive weight may magnify reproductive abnormalities in women with PCOS, and that obesity is prevalent in women with PCOS.
However the levels of obesity seen in women with PCOS may just reflect the current prevalence of obesity in the general population as a result of poor diet and lack of exercise.
The authors continue by saying it is possible that loss of weight may improve the social, psychological and sexual health issues experienced by these women. One conclusion they arrive at, is that PCOS is a “major economic health burden that is likely to expand together with obesity”.
What does the NHS Knowledge Service make of this study?
This is not a systematic review of the subject and although the opinions of experts are helpful, we need to make decisions based on systematic reviews that we know to be free of bias.
In general, the news report appears to have taken the journal article slightly out of context. The journal article is a general consideration of the problems of PCOS and its links with fertility problems, weight and other medical health issues.
Although there are links between PCOS, obesity and infertility, these are all very complex subjects with multiple factors being involved in the causes and presentation of each.
This story may cause unwarranted anxiety for couples where infertility is an issue.
Much further research and observation is needed in this area before any conclusions can be made. Any advice given at this stage would be that, regardless of fertility or medical problems, healthy eating and exercise are the most sensible lifestyle choices.
Sir Muir Gray says...
Reviews that are not systematic are not a basis for action by patients, clinicians or managers.