That Might Be More Than a Baby Bump

Diet snacks might seem like a good way to cut calories, but a new study suggests even indirect exposure in the womb is enough to trigger obesity.


Reaching for the diet version of a favourite treat might seem like a good way to cut calories, but new research from the University of Calgary suggests that ‘diet’ sweeteners might be having the opposite effect.

Building on previous research that links artificial sweeteners with weight gain, a team of researchers looked specifically at the impact of consuming low-calorie sweeteners in pregnancy.

Led by Raylene Reimer, a professor at the Cumming School of Medicine and Alberta Children’s Research Institute, the team focused on artificial sweetener aspartame, and stevia, which is extracted from a plant native to South America.

At 200 to 400 times sweeter than sugar, these low-calorie alternatives continue to grow in popularity. And although deemed safe during pregnancy and breastfeeding, this study suggests otherwise.

“Low-calorie sweeteners are considered safe to consume during pregnancy and lactation. However, evidence is emerging from human studies to suggest they may increase body weight and other cardiovascular risk factors,” explains Reimer.

“Even stevia, which is hailed as a natural alternative to aspartame and other low-calorie artificial sweeteners, showed a similar impact on increasing offspring obesity risk in early life.”

The researchers fed three groups of pregnant and breastfeeding rats a high fat and sugar diet. Each received water, one plain, one with added aspartame, and one with stevia.

Three weeks after birth, pups exposed to sweeteners were significantly heavier and had higher body fat levels than controls, a trend that persisted long-term.

To understand how, the researchers looked at the pup’s gut microbiota. This community of trillions of micro-organisms plays an important role in health and disease. While there are gaps in our knowledge of this area, microbiota changes and resulting disruptions in blood glucose control are thought to play a role in weight management.

To test this, the researchers transplanted fecal matter from pups exposed to low-calorie sweeteners into sterile mice. Even though the donor pups had never consumed sweeteners, the recipients still gained weight.

For the researchers, this suggests that low-calorie sweeteners are not entirely sweet and innocent. If even indirect exposure is enough to trigger obesity, we need to understand more.

“A healthy pregnancy, including good nutrition, is important for a healthy baby,” explains Reimer. “Our research will continue to examine what makes an optimal diet, and more importantly, seek to find ways to correct disruptions to gut microbiota should they occur.”

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Amy Noise is a science communicator who is fascinated by how and why the world works. Always learning, she is passionate about science and sharing it with the world to improve and protect our health, society and environment. Amy earned her BSc (biology and science communication) at the University of Manchester, and MSc (nutrition science and policy) at King’s College London, UK. She tweets sporadically @any_noise