 Whether
too heavy or too thin, women don't appreciate how their
weight can affect their fertility says Dean Van Vugt,
PhD, who discussed the relationship between adiposity
and reproduction at the recent annual meeting of the
Canadian Fertility and Andrology Society in Ottawa.
Dr Van Vugt demonstrated that when
a woman's weight is off balance, her hormonal response
to changes in caloric intake can be more effective than
either medication or assisted fertility technologies,
and cost far less to boot. But frontline physicians—GPs
and gynecologists—often fail to get this message
across.
HEAVY
WITHOUT CHILD
For the past four years, Dr Van Vugt, a professor and
researcher of reproductive endocrinology and fertility
at Queen's University, has been investigating the relationship
between fertility and the appetite-regulating hormone
leptin.
Leptin sends signals to the brain
when a person has had enough to eat. But in obese individuals,
leptin receptors are desensitized. Treatment with leptin
to reduce appetite has proven ineffective.
Leptin also signals a person's
nutritional status to various parts of the body, including
the reproductive system. Dr Van Vugt showed that an
abnormal nutritional status — either a chronic
deficit or surplus of calories — has a greater
impact on a person's neuroendocrine appetite-fertility
axis, and therefore their ability to conceive, than
when their BMI value is within the normal range of 18
to 25 kg/m2.
It's clear that excess weight inhibits
reproduction. Dr Van Vugt cited an Australian study
published in 2004, where 90% of obese, infertile patients
who successfully completed a six-month weight-loss program
resumed spontaneous ovulation.
Yet despite all the evidence, he
says physicians often send overweight women straight
to fertility experts, rather than explaining how shedding
a few pounds might do the trick — and then helping
patients do it. The number of obese women being treated
at fertility clinics is disproportionate to their percentage
in the general population, he says.
"Perhaps there's a taboo when talking
about weight issues," Dr Van Vugt suggests. But while
tact is certainly required, physicians may be surprised
to find that women are likely to welcome advice once
they understand what's at stake. "Of course, it's not
enough to tell a woman 'go lose weight and your fertility
will improve'. Empower them to understand how they can
single-handedly improve their odds of having a baby.
"It's incumbent upon a doctor to provide information
on programs and methods that will facilitate lifestyle
changes," adds Dr Van Vugt. A support group may be a
good place to start. "Part of the reason the [Australian]
study achieved such impressive results is that the weight
loss therapy was delivered in a group setting," he says.
IS
LESS BEST?
Although obesity is a more statistically important fertility
issue, the effects of under-nutrition are more dramatic.
The bulk of Dr Van Vugt's research has involved studying
the effects of leptin administration on underweight,
amenorrheic rhesus monkeys.
Fertility decreases dramatically
as a woman's BMI descends below 18, whether due to anorexia
nervosa, bulemia nervosa or exercise amenorrhea. Almost
total ovulatory dysfunction occurs when a woman reaches
the starvation stage, with a BMI below 15.
Dr Van Vugt's research team found
that, as with obese patients, leptin replacement wasn't
enough to re-initiate menstrual cycles in underweight
primates, who lacked the energy stores necessary to
support reproduction.
This contradicts a recent clinical
study in which leptin did appear to stimulate ovulation
in women. Dr Van Vugt ascribes the discrepancy to the
degree of starvation endured by the respective test
subjects. "The women who ovulated while on leptin were
fairly close to normal BMI, whereas we were producing
a state of energy restriction close to anorexia nervosa,"
he says. The greater the nutritional deficiency, the
harder it will be for the woman to conceive. And when
you're dealing with an eating disorder — particular
anorexia nervosa, which is subject to a high relapse
rate — it can take years to get the body back on
track.
The good news is that physicians
are more inclined to treat an underweight patient's
nutritional state before fertility therapy is considered.
But what about patients who've recovered from an eating
disorder or who were previously competitive athletes
and now look perfectly healthy? Up to 17% of women presenting
with infertility have or have had an eating disorder
and did not disclose it, according to a 2004 study.
Dr Van Vugt says that while women can't be coerced into
telling you if they've suffered from an eating disorder,
patients with irregular menstrual periods should be
thoroughly evaluated. "Community physicians really need
to talk frankly, but honestly, about weight-related
fertility issues," he says.
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