Rates of obesity have been rising in the United States and Western Europe for the past few decades. But in recent years, people in other parts of the world are becoming obese as well — places such as Australia, India, China and Southeast Asia. And, as Rose Hoban reports, with the rise of obesity has come an increase in Type 2 diabetes.

Obese people can develop Type 2 diabetes

People who gain weight are much more likely to develop Type 2 diabetes, characterized by increased levels of sugar, or glucose, in the blood. But Duke University researcher James Lane believes blood glucose can become elevated from more than just eating too much. The North Carolina-based scientist has been studying what happens to the blood glucose of diabetic patients after they drink caffeine.

He recruited 10 adults who had Type 2 diabetes and who were also daily coffee drinkers.

"We used a new, innovative technology that enables us to measure glucose levels in these people continuously for three days," he explains. "On one of these three days, we gave them caffeine capsules, equal to about four cups of coffee. And on the other days we gave them placebo capsules that contain no active drug."

Increased blood glucose is a problem because over time it causes damage to the body, leading to kidney disease, blindness and circulatory problems. Lane and his colleagues found that in his diabetic patients, blood glucose levels were higher throughout the days they had caffeine.

"On average, the levels were 8 percent higher," Lane reports. "We found that the response was to the meals. In other words, the glucose rise that occurred after each of the three meals was significantly larger on the day that they had caffeine as well." For example, Lane says blood sugar levels after dinner were more than 25 percent higher on days when subjects had caffeine than on their non-caffeinated days.

He says scientists aren't really sure why caffeine seems to push up blood glucose levels. One is that caffeine may interfere with the transport of glucose from the blood into the cells. "Another is that caffeine may stimulate the liver to continue to produce and release glucose into the blood even when it's not needed," Lane suggests. "This would be part of the fight or flight response, which normally occurs when we're under stress."

Lane says this research needs to be repeated on a larger scale to test if this phenomenon applies across diabetic populations. If that's the case, this could change the advice doctors give to their patients about drinking coffee, tea and other caffeinated beverages.

Lane's research is published in the journal Diabetes Care.