APPETITE MAY BE HARD-WIRED 

For those who struggle to lose weight, the problem might lie in their brains, not their stomachs. Researchers have found that our natural appetite could be built into our brains just after birth, and may then be set for the rest of our lives.

Richard Simerly and colleagues from the Oregon Health and Science University, Portland, Oregon, examined the role of a hormone called leptin in brain development and obesity, by using mice genetically engineered not to produce that hormone.

Leptin is secreted by the fat tissue in our bodies and regulates our appetite. The more leptin is present, the less hungry we are.

When these genetically engineered mice are left untreated, their lack of leptin makes them grow fat as adults. But when given leptin in the first few week of their life, the growing mice eat much less.

When Simerly looked at the brains of his mice, he found that there were more neurons in the part of the brain that controls hunger in mice given the leptin dose. "The changes are permanent," Simerly says. The team reports their findings this week in Science¹.

The team speculates that these extra neurons prompt a higher level of activity in that part of the brain, helping to stimulate the impulses that makes an animal feel full. The changes, made shortly after the mice are born, probably help to control food intake later in life, Simerly says.

“This is a fundamental finding,” says Sadaf Farooqi from the University of Cambridge, who also studies obesity.

Fighting the fat

The results indicate that our natural weight level is wired into our brains from our early childhood, Simerly says. He adds that the amount of leptin in our systems in those first few weeks of life is controlled by genetics, not by what we are fed.

Knowing how leptin affects our brain could help us develop drugs to counteract obesity, says Farooqi. Some drugs are already available that mimic leptin’s appetite reducing properties, but the new work should better direct drug creation.

This is welcome news for some. The US Centers for Disease Control says that obesity may soon overtake smoking as the single biggest cause of preventable deaths in the United States. Being heavily overweight increases the risk of life-threatening problems such as type-2 diabetes, certain types of cancer and gall-bladder disease.

The World Health Organisation (WHO) estimates that obesity-related diseases account for up to 7% of health-care costs in developed countries.

The best way to reduce weight is to eat more fruits and less fat, and to get at least 30 minutes of exercise a day, the WHO suggests. Although this is a good start for most of us, drug treatment might be the only option for some extreme cases of obesity, says Farooqi.

References

1. Bouret, S. G., Draper, S. J. & Simerly, R. B. Science, 304, 108 - 110 (2003).|Homepage|

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