Many people who start a new diet reduce or eliminate sugary foods and beverages to improve their health. Some eating plans, such as the carnivore diet, remove nearly all dietary sources of sugar and carbohydrates.
However, a new study in mice suggests that completely eliminating sucrose, commonly known as table sugar, from a low-fat diet may have negative effects on gut and metabolic health.
Researchers fed mice a sucrose-free, low-fat diet for 16 weeks and found they developed impaired glucose control and experienced significant changes in their gut microbiome compared with mice fed a low-fat diet containing sugar.
The researchers presented their findings at ENDO 2026, the annual meeting of the Endocrine Society. These findings are yet to undergo peer review.
Sugar can be found in many foods and may be present naturally, such as in fruits, or it may be added, such as in soda or candy.
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Excess added sugar consumption has been linked to obesity, type 2 diabetes, and cardiovascular disease, leading many people who want to improve their health to try low-sugar or sugar-free diets.
In the new study, researchers looked into the effects of a sugar-free, low-fat diet in mice.
The researchers divided 12 healthy mice of similar weight into two groups. The control group consumed a low-fat diet containing sugar, while the other ate a sugar-free, low-fat diet.
Both groups received similar calorie amounts to rule out differences in food amounts contributing to findings.
Over the study period, the researchers tracked multiple markers of metabolic health, gut health, and inflammation. They wanted to see how the mice processed glucose and responded to insulin, and also how the composition of each group’s gut bacteria changed over time.
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At the end of the study, body and liver weights remained similar between the two groups.
Despite no differences in weight gain or calorie intake, mice on the sugar-free diet showed signs of worsening metabolic health.
This group of mice showed evidence of impaired glucose tolerance and reduced insulin sensitivity, both of which are linked to an increased risk of type 2 diabetes.
The researchers also observed significant changes in hormones involved in metabolism and appetite regulation, as well as lower fasting insulin levels.
One notable finding of the study involved changes in the gut microbiome and inflammation in the sugar-free mice. The researchers found lower levels of several beneficial bacteria that help support gut health and regulate inflammation, including Lactobacillus murinus.
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Additionally, they noted an increase in bacteria linked to inflammatory conditions which was accompanied by signs of inflammation in the colon.
Another concerning change the researchers noticed in the sugar-free mouse group was that they developed signs of fatty liver disease and liver inflammation.
While more research is needed to determine whether these findings apply to humans, the results suggest that eliminating sucrose from a low-fat diet may alter the gut microbiome and affect metabolic health, highlighting the importance of overall dietary balance.
Mir Ali, MD, bariatric surgeon, bariatric medicine specialist, and medical director of MemorialCare Surgical Weight Loss Center, spoke with Medical News Today about the study.
“I was surprised to see this result, as reducing carbohydrate and sugar intake is the mainstay of a number of successful weight loss strategies,” Ali, who was not involved in this research, said.
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He noted that a large body of research supports the health benefits of reducing added sugar intake and cautioned against overinterpreting the findings.
“Overall, I think the positive benefits outweigh the possible negative effects,” Ali offered.
Ali mentioned that further studies need to focus on humans to see whether these results carry over. He also discussed the strategy he suggests for his patients who are trying to lose weight.
“What I recommend to my patients on a weight loss journey is that they should emphasize protein and vegetables in the diet and reduce carbohydrates and sugars,” Ali told us. “There is enough evidence to support that this is better for burning fat and overall metabolic health.”
Nneoma Oparaji, MD, a Houston-based physician specializing in lifestyle medicine and obesity medicine, likewise not involved in this research, shared her thoughts on the study with MNT.
“The study is intriguing because it challenges the oversimplified idea that removing sugar is automatically beneficial,” Oparaji said.
She added the caveat that the study should not be interpreted to mean that sugar is healthy, but said that “nutrition is more complex and nuanced than removing a single ingredient.”
Oparaji noted that changes in the gut microbiome may be one of the study’s most important findings because gut bacteria “regulate glucose metabolism, insulin sensitivity, and inflammation.”
“The biggest takeaway is not to focus on a single nutrient or single study. Healthy eating is about overall dietary patterns, not a single ingredient.”
– Nneoma Oparaji, MD
