The researches performed by
Jessica R. Gugusheff and her colleagues from the FOODplus Research Centre in
the School of Agriculture Food and Wine at the University of Adelaide in
Adelaide, Australia offer us a potential explanation for the ever expanding
obesity epidemic. The results may offer answers to why some people are obsessed
to junk foods while others are not.
Experiments in rats showed that a high fat and high sugar diet caused
changes in the fetal brain reward
pathways. This altered the food
preferences of pups. The latest study, published in the March 2013 issue of
FASEB, explores whether the increased preference for junk food could be
attributed to changes in μ-opioid receptor expression in the brain pathway
responsible for memory, motivation, desire and addiction.
An opioid is a psychoactive
chemical like dopamine that works by binding to opioid receptors (binding sites
made of protein), which are found principally in the nervous system and the
gastrointestinal tract. The opioid receptors sense opioid molecules outside the
cell and activate chain of events that converts the message "this molecule is
present" to a physiological response.
For the experiment, the
researchers selected pregnant and lactating rats and divided them into two
groups - one group was fed junk food (JF) and the control group was fed a
regular rat diet.
After weaning, the pups were
given daily injections of opioid antagonist naloxone, to block opioid
signaling. Opioid antagonists prevent the release of dopamine, a
neurotransmitter that helps control the brain's reward and pleasure centers,
thus causing lower intake of fatty and sugary foods (or junk food in this
Researchers noted that naloxone
was less effective at reducing fat and sugar intake in the pups of the junk
food fed mothers.
The study confirmed the
hypothesis that junk food diet, rich in energy, 'bad' fat, sugar and salt,
consumed by a pregnant mother may cause changes in the development of the
opioid signaling pathway in the brains of their unborn children. In other
words, what the junk food does is it reduces sensitivity to the opioids (that
produce 'feel good' chemicals) and the child builds up a greater tolerance to
that food and needs to eat more of it to achieve satiation.
"The results of this
research will ultimately allow us to better inform pregnant women about the
lasting effect their diet has on the development of their child's lifelong good
preferences and risk of metabolic disease," said Beverly Muhlhausler,
co-researcher of the study. "Hopefully, this will encourage mothers to make
healthier diet choices which will lead to healthier children".
'This study shows that addiction
to junk food is a true addiction,' said Dr Gerald Weissmann, editor of FASEB.
'Junk food engages the same body chemistry as opium, morphine or heroin', he
continued, 'Sad to say, junk food during pregnancy turns the kids into junk
: Gugusheff JR, Ong ZY, Muhlhausler BS. A maternal
"junk-food" diet reduces sensitivity to the opioid antagonist
naloxone in offspring postweaning. FASEB J. 2013 Mar;27(3):1275-84. doi: