From healthcentral.com
Zero sugar doesn’t mean zero impact on your body. Artificial sweeteners can affect your gut microbiome, glucose tolerance, and more
If you’ve ever thought to yourself that diet soda seems almost too good to be true—sadly, you might be right. These bubbly drinks may have zero calories and zero sugar, but a growing body of research is demonstrating that the artificial sweeteners in them do affect the metabolism and your ability to lose or maintain weight.
“It’s fascinating how many people view diet sodas and other zero-calorie sweetened drinks as comparable to water,” says Whitney Stuart, R.D.N., a dietitian in Dallas, TX, and the founder of Witness Nutrition consulting. “Artificial sweeteners can have distinct impacts on our bodies that extend well beyond just the calorie count. Research shows they can influence gut microbiota, glucose metabolism, and insulin sensitivity, though these effects can vary from person to person,” she adds.
The effects of artificial sweeteners (sometimes called non-nutritive sweeteners, or NNS) on metabolism are complex and still not fully understood by experts. Different types of sweeteners (such as aspartame, saccharin, sucralose, or stevia) may have different outcomes, and how often you ingest them also makes a difference. “In the short and immediate term, there doesn’t seem to be an impact on metabolism [from NNS]. But paradoxically, long-term use is associated with obesity, type 2 diabetes, and cardiovascular disease,” says Sarah Fishman, M.D., Ph.D., a diabetes and weight loss specialist with Premier Endocrinology in New York City.
How Artificial Sweeteners Affect the Metabolism
Experts have several theories as to why NNS have the potential to derail your weight management plans. One of the most well-supported is that artificial sweeteners appear to change the gut microbiome in ways that have downstream effects on insulin sensitivity and glucose tolerance.
Artificial sweeteners may lead to gut microbiota dysbiosis, which occurs when the balance between the good and bad bacteria in your GI tract tips in the wrong direction, favouring the “bad,” according to recent research in the journal Frontiers In Nutrition. When this happens, levels of anti-inflammatory short-chain fatty acids (a by-product of gut bacteria’s digestion of fibre) drop, which can affect the body’s ability to metabolize glucose and fat. Researchers believe these changes may be linked to an increased risk of obesity, insulin resistance, type 2 diabetes, metabolic syndrome, and heart conditions like high blood pressure.
In one study in the journal Nature, mice given saccharin and sucralose for just two weeks experienced a disruption in their normal gut microbiota and impaired glucose tolerance. And 2023 research from Cedars-Sinai Medical Center in Los Angeles found that people who ingested NNS had significantly different gut bacteria and higher levels of inflammatory markers in the duodenum, the first part of their small intestines, than those who didn’t.
Potential to Rouse the Sweet Tooth
Another hypothesis about why artificial sweeteners affect the metabolism focuses on the sweet taste receptors in the mouth and GI tract. Some experts believe that when sweet taste receptors in the mouth are activated, it tells the brain to expect calories; since NNS activate these receptors but don’t deliver calories, it leads us to crave high-calorie foods, which could lead to overeating, Dr. Fishman explains.
There’s also a theory that artificial sweeteners activate sweet taste receptors in the gut, but since there’s no accompanying rise in glucose (as there would be if you ate real sugar), the body releases less GLP-1, a.k.a. glucagon-like peptide-1, a natural hormone released from the intestines when you eat that has an impact on blood sugar levels, appetite, digestion, and weight. This in turn leads to faster gastric emptying and less satiety—also ultimately leading to overeating, per a 2024 review in the journal Nutrients.
“Sweet-tasting drinks, even with no calories, can increase cravings for actual sugar or carbs, potentially leading to overeating and weight gain,” Dr. Fishman adds.
That said, the human research into these outcomes are mixed, and it’s unclear whether artificial sweeteners really affect sweet taste preferences or overall energy intake. It also may be true in some cases, but heavily dependent on other factors, such as which NNS you’re eating, what you’re ingesting it with, whether you have any pre-existing conditions (including obesity) and more. “A popular belief is that artificial sweeteners universally heighten sugar cravings, but research shows that this isn't always the case,” Stuart says. “The effects are deeply influenced by individual habits and circumstances.”
Can Artificial Sweeteners Help You Lose Weight?
“Artificial sweeteners can be a smart and helpful tool in reducing sugar intake, but they aren’t a metabolic ‘free pass,’” Stuart says.
For someone who’s just starting a weight loss journey or trying to get past a plateau, artificial sweeteners could have a place, Dr. Fishman says. “In the short term, replacing added sugar with sweeteners can lead to weight loss,” she says. But because long-term use has been associated with obesity, she says her advice is to try to use less sugar, rather than replace sugar with a faux sweetener. “For example, if you usually use four sugars in your coffee, try slowly going down to three, then two, then one, rather than replacing [the sugar] with artificial sweetener,” she says.
If you do eat or drink artificially sweetened foods and beverages, though, there are steps you can take to minimize their metabolic impact.
For one, be thoughtful about the types of NNS you’re ingesting. In particular, consider trying to limit your intake of aspartame and saccharin; they’re some of the most-researched sweeteners, and best-existing evidence indicates that all three sweeteners can influence gut bacteria and the body’s response to glucose, Stuart says. Sucralose is another NNS to limit, as it’s also been shown to impact gut bacteria, Dr. Fishman adds. Meanwhile, stevia and monkfruit seem to have less of an impact on gut bacteria and glucose tolerance.
Most artificial sweeteners, like sucralose and saccharin, end up in your gut microbiome largely unchanged, where they can directly interact with gut bacteria, notes Dr. Fishman. “In some cases, these sweeteners even act a bit like antibiotics, suppressing certain strains. They can also change the way gut microbes function, including how they produce metabolites that affect our metabolism,” she explains. “Stevia seems different because its sweet compounds are broken down by gut bacteria into steviol, which the body absorbs and clears, so there’s much less direct exposure for the microbiome.” It also doesn’t have strong antimicrobial effects and doesn’t act as a food source for specific bacteria. Stevia isn’t protective, but because it doesn’t linger in the gut the way other sweeteners do, it isn’t as damaging, she adds.
How you’re taking them in matters, too, Stuart says. For instance, pairing artificial sweeteners and carbs together (such as having a diet soda and a side of French fries) may impair insulin sensitivity more than eating the sweeteners alone (sipping a diet cola for a midday caffeine boost), per recent research in the journal Cell Metabolism.
Carbs have many of the same effects as NNS: They alter the gut microbiome in ways that interfere with how the body handles glucose and activate sweet taste receptors in the gut, leading to high post-meal blood sugar levels, Dr. Fishman says. “Overall, while NNS alone are generally considered safe for blood sugar, consuming them alongside carbs can amplify their impact on the gut and metabolism,” she notes.
With Fake Sweeteners, Be Strategic
Although science has recently shown real benefits to going cold turkey with non-nutritive sweeteners in terms of helping to reverse type 2 diabetes, there are ways to be smarter about including them in your diet so that they don’t trip up your health goals.
But if NNS are part of your diet, “taking probiotics regularly… can help protect your microbiome,” Dr. Fishman suggests as a potential gut-health booster in general. Just be sure to check with your doctor before taking any supplement.
Stuart adds that eating fibre, protein, or healthy fats alongside an artificially (or actually) sweetened drink or food can boost satiety and reduce the likelihood of overeating later on.
Stuart suggests a balanced approach. “Incorporate plenty of water, minimally processed foods, and ensure meals include protein and fibre. Use artificial sweeteners thoughtfully to enhance your meals on occasion, rather than defaulting to them,” she says.
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