A

ustralia is currently ranked as one of the fattest
nations in the world. The Australian Bureau of
Statistics reports that a staggering 15 million
(63%) Australians are overweight (BMI>25,
8.5 million) or obese (BMI>30, 6.5 million),
and that the biggest increases are being seen in the morbidly obese
class (BMI>40). Obesity is a known risk factor for debilitating
diseases including type 2 diabetes, heart disease and cancer.
More recently the impact on younger people of reproduc-
tive age has become evident, with an increased prevalence of
obesity coinciding with a decrease in fertility and increased
reliance on assisted reproductive technologies (Fig. 1).
It is well-accepted that a woman’s lifestyle affects her fertility,
with obesity just as detrimental as smoking and alcohol
consumption. It is also becoming clear that obesity impairs a
man’s fertility. Couples who have at least one overweight or
obese partner take longer to become pregnant, and are much
more likely to be infertile or to require assisted reproduction.
There are many reasons why this occurs.

High blood sugar levels and insulin resistance, which are

associated with obesity, have widespread effects on female repro-

ductive organs, including altered hormonal signals from the

brain that lead to abnormal menstrual cycles and anovulation.

Polycystic ovary syndrome (PCOS) is an endocrine disorder

that is tightly linked to obesity; depending on ethnicity, 30–50%

of women with PCOS are overweight or obese. These women

are not only predisposed to metabolic disruptions such as

dyslipidaemia and insulin resistance, they also present with

impaired ovarian function and anovulation in many cases. Clin-

ical evidence suggests that the severity of PCOS symptoms

correlates with increased adipose tissue. Evidence from animal

studies suggests that the continuous production of pro-inflam-

matory factors, primarily from adipose tissue, disrupts ovarian

follicular dynamics.

The negative effects of obesity on ovarian function also

decrease the quality of a woman’s eggs. The oocytes from obese

women often show delayed maturation and meiotic defects,

malfunction of cellular structures, and altered epigenetic profiles.

JAN/FEB 2016|| 23

THE BIGGEST

FERTILITY ISSUE

TOD FULLSTON, JEMMA EVANS & MACARENA GONZALEZ

Emerging evidence indicates that an obese mother or father predisposes their child to obesity
via nutritional signals conveyed before birth.

Olivier Le Moal/Adobe