The notion that completely cutting out sugar is essential for weight loss and disease prevention may be a widespread myth, according to Dr. Madusha Peiris, an expert in gut hormones and appetite regulation. Peiris suggests that the perceived benefits of sugar restriction often stem from a broader reduction in ultra-processed foods, leading to an overall improvement in diet quality.
While excessive consumption of added sugars can contribute to weight gain and increase the risk of conditions such as type 2 diabetes, fatty liver disease, and heart disease, not all sugar sources are equally detrimental. Attempting to eliminate all forms of sugar could mean unnecessarily excluding nutrient-rich foods like fruits, vegetables, and dairy.
"The key thing to remember is that not all sources of sugar are the same," Dr. Peiris stated. "Sugar occurs naturally in many different foods and also appears in numerous processed forms." She distinguishes between sugars found naturally in foods like fruit and those added in large quantities to highly processed products such as fizzy drinks. From a gut-health perspective, foods with naturally occurring sugars can be part of a balanced diet. Peiris advises against eliminating entire food groups, as this can lead to the loss of essential fiber, vitamins, and other nutrients vital for gut function.
A recent study involving mice, led by researchers at the Dasman Diabetes Institute, explored the metabolic effects of completely removing sucrose from a low-fat diet. The mice fed a sucrose-free diet exhibited poorer glucose tolerance, reduced insulin sensitivity, and increased inflammation in the gut and liver compared to those on a sucrose-containing diet. However, no significant difference in body weight was observed between the groups. These findings, while from an animal study and not directly applicable to humans, suggest that the relationship between individual nutrients, the gut microbiome, and metabolic health is complex.
"Without enough carbohydrate, some people may feel tired and find it harder to concentrate," Dr. Peiris noted. "The important point is that sugar is not inherently harmful in every context. Its effects depend on the source, quantity and overall quality of the diet."
Dr. Peiris also touched upon the mechanisms of weight-loss drugs like Wegovy and Mounjaro, which mimic hormones involved in appetite and blood-sugar control, such as GLP-1. This hormone, released by the gut after eating, signals fullness to the brain, supports insulin release, and slows stomach emptying. "It is all about fullness signals," she explained. "GLP-1 is a hormone produced in the gut that sends satiety signals to the brain, and its release can be stimulated by nutrients in food."
Ultra-processed foods, according to Peiris, often lack the strong gut-brain signaling that promotes satiety. The negative reputation of sugar is partly attributed to foods high in sugar often being calorie-dense and containing additives, which can lead to increased inflammation if caloric intake exceeds expenditure. "The best way to lose weight is to gradually reduce your calorific intake... and to do that you need to feel full, so just cutting out sugar in a low fat diet may not make a difference," she said.
Consistently high blood sugar levels and rapid spikes and crashes, resulting from quick absorption into the bloodstream, can increase the risk of diabetes. "It's free sugars which cause a huge energy surge and then a crash... which can cause harm, rather than simply eating a piece of fruit," Dr. Peiris stated.
UK guidelines recommend that adults consume no more than 30 grams of free sugars per day, defined as sugars added to foods and drinks. Sugars found in whole fruits, vegetables, and honey are generally better tolerated and processed differently by the body. "That's why eliminating sugar from your diet probably doesn't make a lot of sense; we've evolved eating vegetables and a bit of fruit so our bodies have adapted to need sugar, in the form of glucose, to function," Peiris concluded. She emphasized the importance of a diet rich in fiber, protein, and diverse nutrients to optimize satiety signals.