Artificial sweeteners are used by millions to cut their calorie intake and lower sugar consumption. They can be added to drinks or sprinkled over food.
The thinking is that these sweeteners, which have few or no calories, are better for the waistline and don’t increase blood sugar levels.
But a number of studies have suggested they may not be as helpful to losing weight as often thought, and may even trick the brain into feeling hungry.
Professor Reimer and colleagues split the pregnant rats into three groups. Some were given aspartame, which is used in Diet Coke, others were given stevia which is used in 7UP Free.
A third group of pregnant rats were given water, allowing the researchers to detect any differences between the groups.
Their pups were weighed as soon as they gave birth with tests carried out to see how their mother’s diet affected their gut bacteria.
Just like humans, rats have a community of microscopic life in their digestive system that helps break down food.
Barely any effects were visible on the rats which had given birth, the researchers wrote in the journal Frontiers in Nutrition.
But they found pups born to sweetener-fed mothers were heavier with a higher percentage of body fat.
They also showed higher levels of some microbes and fewer of others.
Researchers believe these changes in their microbiome may explain why they gained more weight.
‘Even though the offspring never consumed the low-calorie sweeteners themselves, their gut bacteria and obesity risk were influenced by the sweeteners that their mothers consumed during pregnancy,’ Professor Reimer said.
‘We found that specific bacteria and their enzymes were linked to how much weight the offspring gained and how much body fat they accumulated.’
A number of other studies have also explored the negative impacts of sweeteners used in diet soft drinks on obesity.
Last year researchers at the University of Southern California tested the impact of sucralose on 74 volunteers and found it actually increased food cravings.
But official NHS advice says research into sweeteners and appetite stimulation is inconsistent and that diet soft drinks can provide a healthier alternative to people with diabetes who need to keep an eye on their blood sugar levels.
Obesity in children is a massive issue in both the UK and the US with up to a third of youngsters in each country considered overweight.