Lack of Leptin a cause of 'plateau' all too familiar to dieters
New York, NY- Dieters know the phenomenon all too well: They cut calories, exercise, and lose some weight but at some point they can't seem to get rid of any more of the excess poundage.
Now researchers from Columbia University College of Physicians & Surgeons, St. Luke's-Roosevelt Hospital Center, and the Weill Medical College of Cornell University, in a study of rats, may have some new clues why the plateau effect occurs and what could be done to overcome it. The findings have led to clinical tests in people.
The investigators theorized that rats--and humans--may not be able to lose weight after a certain amount of dieting, even with drugs or surgery, such as gastric bypass, because the loss of fat decreases the amount of the hormone leptin in the body.
Leptin, a hormone mostly manufactured by fat cells, is present in obese animals (and humans) but as the animal loses fat, levels of the hormone go down. With reduced levels of the leptin, the researchers say, the brain mistakenly thinks the animal needs food and sends signals to the body to slow metabolism down and increase appetite, two conditions that make it harder to fight the battle of the bulge.
Prior research has shown that rats with diet-induced obesity and obese humans both have high levels of leptin. Giving more to them is minimally effective. The researchers in this study, therefore, gave obese rats a mixture of the weight-loss drug sibutramine, known commercially as Meridia, and leptin, to see if the two substances together might help the overweight animals lose weight. The addition of leptin, they believed, would trick the brain into thinking that no weight was being lost.
"By preventing the decrease in leptin levels that normally occurs with weight loss, we theorized that sibutramine would be able to have a greater weight-loss effect," says Carol Boozer, D.Sc., assistant profes
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Contact: Annie Bayne
as862@columbia.edu
Columbia University Medical Center
28-Sep-2001