Tuesday, 14 August 2007

Path to obesity begins in womb, study shows

BLAME your mother if you’re overweight.
Sounds Freudian and perhaps a bit mean, but a breakthrough study on obesity indicates the path to becoming a podgy adult begins in the womb.
Scientists at Auckland’s Liggins Institute, led by director Professor Peter Gluckman, have been experimenting on rats to see if, or how, the nutrition of an unborn baby shapes his or her future.
Their research shows that if a mother has a poor diet during pregnancy, her developing child, or foetus, will predict a life where there is a shortage of food and will set its system to store fat.
This works if the child is born into a life of lack; but there’s a major mismatch when a wee one programmed for famine instead faces a feast, especially one high in fat and thick with fast food.
“It’s a fundamental breakthrough that says that the developmental stage is important, or even more important, in determining the way we live as adults,” Gluckman says.
Our inbuilt prediction system has buttons, which get pushed based on the information and environment a baby learns from in the womb and just after birth.
Gluckman says these buttons are called gene switches, which determine whether a child takes the high road to health or low road to obesity, heart disease and diabetes.
But wait – there’s hope. The direction can be reversed.
Sorry, not for us adults, or for kindergarten-aged kids and older. Your fat fate has already been sealed (although diet and exercise can make a difference).
Back to the rats. In a joint research programme with the University of Southampton in England, Gluckman and his team used the hormone, leptin, to dose the newborn offspring of rats that had been undernourished during pregnancy, and were at risk of growing into obese adults.
Leptin is a naturally occurring hormone that regulates appetite and signals to the body when it has eaten enough. The name leptin comes from the Greek word leptos, meaning thin.
“The pups that were treated with leptin went on to develop normally and did not become obese,” the study says.
Gluckman says early intervention, therefore, offers a chance for babies to turn off the obesity gene switch.
“We have proven it’s possible to do it,” he says, by cellphone from Southampton in England, where he is meeting colleagues.
But the window of opportunity is small. “We suspect, but cannot yet prove, that it’s from conception to a few days after birth,” he says, referring to the rats.
People are likely to have a better chance of change. “For humans – a year or two after birth.”
Gluckman envisages babies being tested to see which gene switch has been turned on, then treated to ensure they are on the path to being slim and healthier.
“Now we have got to find ways to do it that would be biologically meaningful and contextually possible for a human child.”
He doesn’t imagine radical or invasive treatment; instead he foresees the babies will be treated with a programme of nutrition and vitamins to get switched on for the true environment they will face – a world of plenty.
There are two processes that make the timeframe for reversal so brief, he says.
“One – the system itself becomes less plastic as it gets older.”
This means that when an organism is developing, its future is being moulded by its environment, taking signals from what is happening around them.
“Two – the switches do less.”
He says gene switches work throughout life, allowing us to grow, develop and build muscles. But as we grow, the switches don’t react so well, if at all.
Gluckman (left) likens the early gene switch process to what happens with honeybees.
Larvae that are fed royal jelly grow bigger, stronger and turn into queen bees, which can reproduce.
But if genetically identical larvae are fed on other substances, they turn into worker bees, which are smaller. “Imagine trying to have an adult bee turn from a worker bee into a queen bee – it’s not possible,” he says.
That’s why some adults struggle so badly with their weight. They were destined, from the birth, to be big.
So, to help break the cycle of obesity, mothers need to eat a balanced, nutritious diet.
Because that old adage “I’m eating for two” is turning out to be true.

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