Scientists recently discovered neurons that control appetite and metabolism signals in rats, causing weight-control difficulties.
"I think it's a huge breakthrough in terms of understanding how the brain works," said Roger Cone of Oregon Health Sciences University.
Cone helped lead the study, which was published in this month's issue of the scientific journal Neuron.
"This gives us a really solid start to understanding the pathways involved in food-seeking behavior and energy-balance control." he added.
The scientists named the area the "adipostat", meaning it acts roughly as a fat thermostat, and said if it works the same way in people, drug companies might be able to find ways to manipulate it.
For years, scientists believed that such a "thermostat" existed in the brain. Until now, how the mechanism worked was a mystery.
To find the adipostat, researchers traced the routes of two fiber pathways -- one that makes us eat more and another that prompts us to eat less. Both tell the brain to react, but a malfunction can cause a person to overeat.
|Experiments on rats show weight control is due to neurons in the brain.|
Cone, working with pharmacologist William Colmers of the University of Alberta, found the cells in the hypothalamus of rats' brains.
The researchers found that the cells were stimulated by two hormones known to be involved in the regulation of eating -- neuropeptide Y and melanocyte stimulating hormone (MSH).
When neuropeptide Y is injected into the brains of rodents, they store more fat and their metabolisms slow down. When MSH is injected, they get thinner.
The researchers hooked up mice and rats to electrodes and found the particular brain cells stimulated by the hormones.
Understanding the complex interplay of hormones can help doctors explain why dieting can make people gain weight.
It may also eventually help millions of overweight people who shed pounds by dieting, only to regain that weight once they return to their regular eating habits.
"The reason why it's so hard for people to lose weight is because when you decrease your caloric intake your brain thinks something is wrong and it works very hard to get you back up to your old weight," said Cone, a senior scientist at Oregon Health Sciences University.
"The body thinks you're undergoing starvation or disease and it initiates a number of responss to prevent you from losing weight and even to help you put weight back on," he said.
Cone likened the process to a home heating system.
"If you have a really good heating system, opening a window won't lower the temperature in your house because cool air will come in the window but the thermostat will sense a change and tell the heater to crank out more heat,'' he said.
By understanding and reading the adipostat, it may be possible for pharmaceutical companies to design drugs that can block the ability of the brain to respond to a decrease or increase of food intake, Cone said.
The findings could lead to the development of drugs that will help people lose or gain pounds. However, researchers didn't want to even hazard a guess at how long that would take.
"I need to clarify this and say this is a very basic finding and I don't think we can leap from this to a cure for obesity or anorexia, today or tomorrow," Colmers said.