A study tracing the route taken by insulin to the human brain could lead to the development of a pill that allows people to control their appetites and lose weight, a University of Washington researcher said Monday.
Although it is several studies and years away, the pill would mimic the effect of insulin, which in animals has been shown to inhibit appetite and lead to weight loss, said Dr. Brad J. Wallum at the American Diabetes Assn. convention in Anaheim.
Other obesity-related studies presented at the meeting concluded there is a physiological reason for regaining weight after losing it on a diet and that diabetics not dependent on insulin have a "sweet tooth" because they cannot properly taste sugar.
Wallum, who is an association investigator in endocrinology, nutrition and metabolism, said previous studies have shown that when insulin is infused directly into the brains of baboons and rats, the animals have a decrease in appetite and lose weight.
Along with University of Washington associates Dr. Dan Porte and Stephen C. Woods, Wallum presented what is believed to be the first study that shows insulin in humans is transported to the brain by way of the cerebral spinal fluid.
Because of insulin's effect on animals' appetite, "we hypothesize that this is also the case in humans," Wallum said. A study with humans is planned to determine whether increased levels of insulin bring on feelings of satiety, he said. If so, the "anti-fat" pill could be on the way, he added.
"It's several years down the road, but we would like to help people with overweight problems because these people suffer from a number of problems, including high risk for diabetes, problems with arthritis and risk for heart attacks and strokes," Wallum said.
"We would like to offer these people medication as we have for other forms of medical problems, such as hypertension and cardiac disease, to decrease their morbidity and disability."
The University of Washington team became interested in the subject because most non-insulin, or "adult-onset diabetics" are overweight.
"We wondered, since they have inappropriately low insulin levels and are also overweight whether or not insulin may have a role in the control of food intake and body weight," Wallum said.
The study on humans involved eight healthy men and women, ages 20 to 42, who were infused with insulin. Glucose also was intravenously administered to offset the severe blood sugar drop insulin can bring on.
During the five hours that insulin and glucose were infused, samples of cerebral spinal fluid were taken every 30 minutes and registered significantly increased levels of insulin, Wallum said. The next step in the study with humans, he said, will be to determine whether the increased level of insulin in the cerebral spinal fluid suppresses appetite, as it does in animals.
Wallum acknowledged that obesity "is a very complex disorder," brought about by overeating, lack of exercise or a combination of the two. "The branch we're working on is trying to help people decrease the urge to eat. If we can help people overcome the desire to overeat, we hope to control the problem from that standpoint."
But in another study presented at the diabetes convention, a University of Colorado researcher had bad news for people who have lost weight and want to keep it off. There is a physiological reason that those pounds go back on so easily, said Dr. Robert H. Eckel, an associate professor of medicine.
Eckel said it has been known that obese people have a higher level of lipoprotein lipase, an enzyme that tells the body to store fat, than thin people do. His study concluded that even after weight loss, the lipase enzyme continues to be produced in high-level quantities. As a result, the fat cell in the newly thin person is "very responsive to food," and fat is easily regained, he said.
"The fat cell is saying, 'I don't want my activity to fall. I want to keep it high where it once once was,' " Eckel said.
"The fat cells are ready. It's kind of like you have a swimming pool in your backyard that has no water in it. If you give it the water, it will fill very readily. If you have no pool and you're watering the concrete slab, there's nothing that's going to go in. The fat cell is very much ready to be filled," he said.
Consequently a 140-pound woman who loses 25 pounds will gain weight if she eats the same number of calories as a 115-pound woman who has never lost weight, Eckel said. The newly thin person must consume about 15% fewer calories than a person of the same weight who has never had a battle with the bulge, he explained.
Doing away with, or inhibiting the fat-producing lipase enzyme is not feasible, he said, because it also performs the important job of clearing blood fats from the bloodstream.