High amounts of fructose, artificial sweeteners and sugar alcohols can manipulate our gut bacteria so it interferes with our metabolism and fullness signals, Swiss researchers have found.
Researchers at Zurich's Institute of Food, Nutrition and Health have discovered that when gut bacteria process food, short-chain fatty acids are produced, which are crucial for providing our bodies with energy.
But when our guts are subjected to large quantities of artificial sweetener and fructose (a type of sugar used in a lot of sweet foods in the US), they produce a lot more short-chain fatty acids, which impacts satiety signals, Men's Health reported.
"An evolution of the gut flora to this new sweetener-rich environment has a potential to negatively impact our health," said Dr Amanda Payne, lead author of research that appears in Obesity Reviews.
"This signalling may cause disruptions in our feeling full and hence prevent us from stopping to eat when we should," she said.
These short chain fatty acids can also cause the lining of the gut to become inflamed, which can cause bacteria to leak from the digestive tract into the bloodstream, which increases people's risk of heart disease, stroke and diabetes.
Most Australian foods don't use corn syrup as a sweetener, so fructose is not as big a concern for us. But Dr Alan Barclay, spokesman for the Dietitians Association of Australia, told ninemsn it's possible that diet soft drinks could impact our digestive bacteria.
"It's plausible that some of the changes in micro flora in the human gut may be having some influence on obesity, for better or worse; that question is the subject of ongoing research at the moment," he said.
But he said the verdict is still out.
"There are some studies that suggest artificial sweeteners can help with weight reduction as far as reducing calories but there are others that suggest otherwise," he said.
Dr Barclay said the message remains consistent for long-term weight loss: eat a wide variety of unprocessed foods.
"So lots of real wholegrains, less sugars, real whole fruits and vegetables," he said.
"Also, good quality yoghurt and milk which are prebiotics that help encourage good bacteria in the gut. And not too much processed meat; fresh meat is much more preferable. We've always known that is the best solution for long-term weight management."