Researchers at Washington University School of Medicine in St Louis have analysed the sweetener sucralose (Splenda) in 17 severely obese people who didn't have diabetes and didn't use artificial sweeteners regularly.
"Our results indicate that this artificial sweetener is not inert - it does have an effect. And we need to do more studies to determine whether this observation means long-term use could be harmful," said first author M Yanina Pepino, research assistant professor of medicine.
The researchers gave subjects either water or sucralose to drink before they consumed a glucose challenge test. The glucose dosage is very similar to what a person might receive as part of a glucose-tolerance test.
Every participant was tested twice. Those who drank water followed by glucose in one visit drank sucralose followed by glucose in the next.
"When study participants drank sucralose, their blood sugar peaked at a higher level than when they drank only water before consuming glucose," Pepino explained.
The elevated insulin response could be a good thing, she pointed out, because it shows the person is able to make enough insulin to deal with spiking glucose levels.
But it also might be bad because when people routinely secrete more insulin, they can become resistant to its effects, a path that leads to type 2 diabetes.
"Although we found that sucralose affects the glucose and insulin response to glucose ingestion, we don't know the mechanism responsible," said Pepino.
She said further studies are needed to learn more about the mechanism through which sucralose may influence glucose and insulin levels, as well as whether those changes are harmful.
The study was published in the journal Diabetes Care.