Scientists believe the observations made in mice may also apply to humans and could be used to answer how the impulses that tell us to eat operate. They also discovered that despite efforts to change their weight, many people contain a physical "set point" that keeps them at their current weight.
One scientist said that the different wiring system that regulates feeding might vary in people who are obese and those who are thin.
The hormone leptin was discovered 10 years ago and it was found that when it entered the bloodstream, it helped suppress the appetite and lack of it could lead to overeating and obesity. Despite these findings, the notion of losing weight simply by taking leptin hasn’t yet been tested by humans.
In the studies involving mice, researchers looked at the cells in the area of the brain called the hypothalamus, which makes up 1 percent of the brain’s volume and contains some important functions including body temperature, heart rate, blood pressure and food intake. Each region contained two cell types, NPY cells and POMC cells. When NPY cells were stimulated, it was shown that feeding increased and fat accumulated. However, when POMC cells were stimulated, the feeding decreased and ultimately the body mass decreased also.
The actions of these cells were used to analyze how often and how much an animal eats.
The study also revealed that when a mouse experienced leptin deficiency, the NPY cells that induce feeding, were more active and POMC cells became less active, compared to the normal mice whose NPY cells became more repressed.
After the hormone-deficient mice were given leptin, there was a significant reduction in the amount of connections to the NPY cells that promote feeding and a near doubling of the satiety-inducing connections. Researchers have used the results of this study to help them determine the physical "set point." Experts stated that when a person loses fat, leptin levels in the blood drop, which may lead to changes in the hypothalamic wiring, causing NPY cells to stimulate feeding and POMC cells to stop the feelings of satiety.
Other scientists speculated that a person’s sensitivity to leptin, based on how it was formed in their brain just after birth, might affect their susceptibility to obesity in adulthood.
Washington Post April 2, 2004
In a past newsletter, I posted an article on leptin, the mysterious hormone that helps govern hunger and satiety.
While leptin may modify an adult animal's leptin circuitry, it cannot redesign it. For the two-thirds of us who are overweight, the end result remains the same, we will need to optimize our aerobic exercise and eat according to our metabolic type.
If progress is not being made then one needs to seriously examine the emotional factors.
Typically energy psychology techniques are the most useful here. However, even in the best of circumstances there does appear to be a minority of people who do not respond to these approaches.
I have long believed that there is another variable that is not yet fully appreciated. It is becoming clear that leptin physiology may be a substantial contributing factor in this area.
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