parent to child. However, experiments in which animals are
fed a high-fat diet to mimic obesity are able to better pinpoint
how changes to sperm can lead to obesity in offspring.
These animal studies have clearly demonstrated that male
obesity leads to the transmission of obesity to their offspring for
up to two generations. It might be difficult to imagine how
paternal nutritional signals are transmitted to offspring, but
exciting new research is revealing previously unknown molec-
ular components, including epigenetic modifications to the
DNA and microRNA carried by the sperm into the egg. These
molecular components of sperm are modified by obesity, and
likely form part of the mechanism by which the metabolic char-
acteristics of fathers are inherited by their progeny. It is these
changes to sperm that are believed to transmit the signal from
the father to the embryo at fertilisation and program the embryo
on a growth trajectory that results in poor offspring health.
While obesity is clearly detrimental to both male and female
fertility, as well as offspring health, these effects appear to be
reversible. Recent studies of weight management programs for
obese patients undergoing assisted reproductions have shown
promising effects on their fertility.
Clinical and animal studies have shown that a change in lifestyle,
such as exercise and modest weight loss, can improve the fertility
outcomes of overweight and obese women. Interestingly, a mild
exercise regimen during pregnancy improve pregnancy and birth
outcomes in overweight and obese women despite not causing
an effect on their body weight. If weight loss can be achieved, even
a 5–10% reduction in the body weight of obese women improves
metabolic and reproductive parameters such as circulating insulin,
hormone levels, menstrual cycle regularity and ovulation.
Lifestyle changes regarding diet not only influence weight loss
but can increase conception and live birth rates. Dietary inter-
ventions, such as reduced calorie intake, have a positive effect
on the severity of the metabolic symptoms of PCOS, most
likely due to improved insulin sensitivity and a dampening of
chronic inflammation.
The study of the relationship between dietary habits and
fertility outcomes in different communities, and their impact
on disorders like PCOS, open a window for understanding the
importance of a healthy diet on the reproductive health of
women.
Similarly, the discovery of effective interventions that over-
come the detrimental effects of male obesity on fertility and
offspring health are providing promising results. For example,
in an animal model of male obesity, diet or exercise restored
not only fertility but also the molecular make-up of sperm and
the health of offspring. This research is yet to be translated into
the human setting.
There is mounting evidence that either a mother’s or a
father’s obesity can not only impair their own fertility and
chances of conceiving, but also impact on the future health
outcomes of their children. Emerging evidence also suggests
that when both parents are obese that these effects are
compounded. The discovery of effective obesity interventions
that translate into human use will provide both short-term
benefits to the fertility of the individuals undergoing them and
long-term health benefits for future generations.
Tod Fullston is NHMRC Peter Doherty Fellow at The University of Adelaide’s Robinson
Research Institute, where Macarena Gonzalez is a PhD student. Jemma Evans is a Senior
Research Officer at The Hudson Institute of Medical Research.JAN/FEB 2016|| 25... animal studies have
clearly demonstrated that
male obesity leads to the
transmission of obesity to
their offspring for up to
two generations.Kletr/Adobe