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Health

Weighing in on fat and fertility

Last Updated January 21, 2008

Women who want to improve their chances of having children should start by watching their waistlines, says a new U.S. study. And its advice is not just for those with a wider waistline.

The eight-year study of 17,544 women, published in the November issue of Obstetrics and Gynecology, found that those who most closely followed a "fertility diet" had a 66-per-cent lower risk of infertility due to ovulation problems and a 27-per-cent lower risk of infertility due to other causes than those who did not.

The so-called fertility diet emphasizes monounsaturated fats such as olive oil and avocados over trans fats typically found in fast food. It also favours protein and iron from vegetable sources like legumes and spinach rather than red meat, along with low-glycemic carbohydrates like whole grain bread and pasta — and interestingly, moderate consumption of high-fat dairy products.

Staying within what was described as a normal weight range and engaging in regular physical activity were also beneficial, as were cutting down on caffeine and alcohol and cutting out cigarettes.

Obesity

On the heels of this American study, the British Fertility Society has issued new guidelines recommending that doctors deny obese women fertility treatment, and instead require them to lose weight until they�ve reached a body mass index (BMI) of below 30. (That's about 176 pounds for a woman 5-5" tall.)

"Obesity is a significant problem for women trying to conceive, especially since women are having children later in life, when changes in weight and lifestyle are difficult to make," says Dr. Donna Chizen, a professor and researcher of reproductive endocrinology and fertility at the University of Saskatchewan.

Dr. Chizen points to a range of fertility problems faced by overweight women, especially those who obtain a significant proportion of their calories through "empty" carbohydrates, such as white bread and pasta, junk food and soft drinks.

"Overweight women often develop insulin resistance, so their bodies over-produce insulin, leading to an increase in production of the hormone androgen. This effectively shuts down the ovaries, often resulting in an infertility condition called polycystic ovary syndrome (PCOS)," she says.

Dr. Chizen adds that excess insulin can also cause chromosomal abnormalities in a woman�s eggs, drastically increasing the likelihood of miscarriage, pre-term labor, birth defects and fetal demise.

PCOS affects about one in 10 women, most often due to excessive weight, particularly obesity. Dr. Chizen notes that most women aren�t aware they have it, and its wide range of symptoms — from acne and excess hair growth to ovarian cysts and irregular or no menstrual cycles — can make it difficult to diagnose.

If left untreated, it carries a risk of diabetes, cancer and cardiovascular disease. However, PCOS can often be treated by simply losing some weight.

"The weight loss doesn�t need to be drastic. A 10-per-cent reduction in body mass is often sufficient," says Dr. Chizen, meaning someone who is 100 pounds overweight would have to lose about 22 pounds.

Underweight issues

Although the medical community has focused its attention on fertility issues at the heavier end of the scale, the hormonal connection between fat and fertility is even more pronounced in underweight women.

"Many overweight and even obese women can and do conceive, but soon as a woman�s body weight is 15 per cent below the normal range, she stops ovulating," says Dr. Dean Van Vugt, a professor and researcher of reproductive endocrinology and fertility at Queen�s University.

Fertility decreases dramatically as a woman�s BMI descends below 18, or 110 pounds on a 5-5" frame, whether due to an eating disorder or extreme exercise and dieting.

Almost total ovulatory dysfunction occurs when a woman reaches the starvation stage, with a BMI below 15, or 88 pounds and 5-5" tall. A similar shutting down of the reproductive system can occur in women with very low body fat or who regularly burn more calories than they consume, such as elite athletes, crash dieters or severe alcohol abusers.

Pending crisis?

The rise in both obesity and eating disorder rates across Canada, as well as the increasing tendency to delay childbearing until a woman is in her 30s or 40s — when fertility rates drop by 25 to 40 per cent, respectively — is leading many experts to predict a looming fertility crisis.

Dr. Van Vugt and Dr. Chizen both agreed that better education of children and teenagers about the importance of proper nutrition, adequate exercise and maintaining normal weight would help slow this disturbing trend.

"Schools and parents play a much greater role than physicians in promoting healthy living," which has lasting consequences for both individuals and society, says Dr. Van Vugt.

For hopeful mothers-to-be, Dr. Chizen also stresses the importance of taking a multidisciplinary approach to health, consulting experts in exercise and nutrition before seeing a fertility specialist.

"I tell patients to think beyond which eating habits or activities will help them get pregnant. They need to make lasting changes so they will still be around to see their grandchildren. It isn�t just about fertility, it�s about improving one�s life," she says.

The author is a Canadian print and video freelance journalist

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