Tuesday, April 10, 2007
Type 2 diabetes generally results from the combination of impaired beta cell function and insulin resistance acting on susceptible genes. Why then is there such a large overlap between being heavy and type 2 diabetes?
The answer is slowly coming out of research led by three scientists who worked together for years in Seattle. They are endocrinologists Daniel Porte Jr., M.D., who is now associated with the VA San Diego Health Care System, Michael W. Schwartz, who is now professor of medicine at the University of Washington, and psychologist Stephen Woods, now of the department of psychiatry of the University of Cincinnati.
“It's complicated,” Dr. Porte tells me, “because everybody who is obese doesn’t have diabetes, and everybody who has diabetes is not obese. So we have been looking at why they tend to overlap.”
The answer, they found, is the beta cells of the pancreas that make and secrete insulin. “If the beta cells are not functioning properly this will tend to lead to diabetes,” he says. “And this will also tend toward an increase in body weight.”
Insulin has two apparently contradictory impacts on your body, Dr. Porte says. “One is that it tends to store fat. When you eat a meal, the calories will be stored so that you will be able to survive between meals. But the insulin also goes to your brain to suppress your eating – so you won’t overeat.”
Obesity too has “a bunch of causes,” Dr. Porte says. “Diabetes and obesity occur together more than you would expect by chance.”
If you have factors in your genes or your environment that would cause obesity, then you would probably become obese, he says, and your diabetes, if any, would be very mild. But if you have factors that tend to damage the beta cells or to produce insulin resistance, then you would get more severe diabetes.
“So you can get varying amounts of diabetes and obesity,” he says. “But they will tend to occur together because of fact that insulin tends to store fat and tells the brain how fat you are, preventing overstorage.”
Does this mean that Dr. Porte would not call diabetes or obesity a lifestyle disease? “In our view obesity is not very often a behavioral disorder,” he replies. “It is a biological disorder, that is an interaction between the biology and the environment.”
“While obesity is a biological disorder,” he continues, “it is sometime amenable to behavioral intervention. But the difficulty occurs when you intervene behaviorally, because that behavior is fighting the biology. That is one of the reasons why it is so hard to regulate your weight. So we need to come up with ways to help people achieve those goals.”
This is not to deny that we can control our diabetes better when we lose weight. I know from my experience of losing a lot of weight during the past year how much better my numbers are and how much better I feel.
Now, we have begun to have drugs to help people with diabetes regulate their weight. Maybe in a few years as more and more of us lose weight, people will stop blaming us for being overweight and stop labeling type 2 diabetes as a lifestyle disease.
