Regular insulin takes about 45 minutes to work its way into the system -- with the dosage adjusted to the type and amount of food to be eaten, says Jean-Luc Ardilouze, MD, PhD, professor of medicine at University of Sherbrooke in Quebec, Canada.
"Of course, how many of us know exactly what, and how much, we are going to eat 45 minutes before a meal? So the big advantage of short-acting insulin was you could inject it immediately before eating," Ardilouze tells WebMD.
Obesity and Short-Acting Insulin
Ardilouze became interested in the biology of fat tissue. He soon learned that fat tissue has highly restricted blood flow -- and wondered what that meant for obese people who take insulin injections.
When they studied short-acting insulin products, Ardilouze and colleagues discovered that the bigger the dose, the longer the products took to work. They reported the findings at the American Diabetes Association's 67th Annual Scientific Sessions, held June 22-26 in Chicago.
"If you inject 10 units of short-acting insulin into obese subjects, there is not much difference in time to peak effect," he says. "But the time is tripled with triple the dose -- the kind of dose an obese person with diabetes is much more likely to need."
This means that for obese people, short-acting insulin isn't short-acting. Ardilouze says it may take as long as 45 minutes to work -- a fact that doctors and patients don't know.
How could this be? After all, short-acting insulin products are marketed, and priced, on the basis of their convenience. Ardilouze says he was amazed to learn that short-acting insulin was approved by U.S. and Canadian authorities without having been tested in obese people with type 2 diabetes.
"The big surprise when we started this study was to find out that the [biochemical action] of short-acting insulin had been established in young, lean, type 1 diabetics," Ardilouze says. "One product, in the tiny writing on the label, there is one little part that says [it] was never studied in obese people with type 2 diabetes."
That's true, says M. Sue Kirkman, MD, vice president for clinical affairs at the American Diabetes Association.
"The initial trials looking at short-acting insulin were done in normal individuals -- and all of the [biochemical action] studies are done in normal people -- probably lean normal people," Kirkman tells WebMD. "Most studies of rapid-acting insulins are done in type 1 diabetes, although I think there are some type 2 studies, especially with the more recent products."
Getting Good Blood Sugar Control
It's a problem, says ADA President Larry C. Deeb, MD, medical director of the diabetes center at Tallahassee Memorial Hospital and a professor at both the University of Florida and Florida State University.
"I feel very strongly about the issue of testing treatments in the kinds of people who actually are going to get treated," Deeb tells WebMD. "Every human isn't the same. Children aren't the same as adults, and obese people aren't the same as the lean adults you routinely recruit for these studies."
So what should obese patients do when they need insulin? Deeb agrees with Ardilouze.
"You may need to take it earlier," he says. "You aren't going to get rapid action for the obese patient. So you may need to rethink how you do it."
Kirkman says that if patients are worried, they should test how well their short-acting insulin is working.
"And if someone were really concerned, they could just take the insulin, eat the meal, and test their blood glucose in two to three hours," she says.
Neither Kirkman nor Deeb was involved in the Ardilouze study. Ardilouze say he will next study blood sugar control in obese patients taking short-acting insulin for type 2 diabetes.