Sugar Substitutes May Not Help You Lose Weight, New Review Finds

Close-Up Of Sugar And Sweetener Packets In Container At Cafe.
(Image credit: Sharon Pruitt/EyeEm via Getty)

Sugar substitutes are found in everything from diet sodas to sugar-free candies, but scientists continue to debate whether these non-sugar sweeteners are really good for you.

Now, a new review study suggests sugar substitutes don't seem to be hugely beneficial. Indeed, the researchers conclude there's no "compelling evidence" for important health benefits from non-sugar sweeteners. In their review, the researchers assessed a variety of health outcomes, including body weight, body mass index (BMI), blood sugar levels, eating behavior, heart disease and cancer. [7 Biggest Diet Myths]

Although the new work is one of the most comprehensive reviews on the topic to date, it's far from the final word on sugar substitutes. The researchers stress that many studies conducted so far on the benefits of sugar substitutes are lacking in scientific rigor. For example, many studies included in the review were small or conducted over short periods. For this reason, larger studies conducted over longer periods are needed to draw firmer conclusions on the benefits and harms of sugar substitutes, the researchers said.

The study, published Jan. 2 in the journal The BMJ, will help inform upcoming guidelines from the World Health Organization on non-sugar sweeteners.

Sugar substitutes and health

Sugar substitutes include both artificial sweeteners — such as aspartame and saccharin — and"natural" no-calorie sweeteners, such as stevia. Because sugar substitutes add few to no calories to a person's diet, they could, in theory, reduce the risk of weight gain. But the evidence for health benefits from sugar substitutes is mixed, the researchers said. Some studies have linked consumption of sugar substitutes with a reduced risk of obesity and type 2 diabetes, but other studies suggest the opposite — that non-sugar sweeteners may actually increase the risk of obesity and diabetes.

To clarify the health effects of sugar substitutes, the researchers reviewed information from 56 previous studies that compared people who used sugar substitutes with those who did not. The studies included both adults and children who were generally healthy. Studies were included only if they listed the type of sugar substitute.

For the most part, people who used sugar substitutes had similar health outcomes to those who did not.

Some small studies did suggest slight improvement in BMI and fasting blood glucose levels (high levels are linked to diabetes) among people who used sugar substitutes. But the quality of this evidence was low, the researchers said. Among adults and children who were trying to lose weight, there was no evidence of any effect from sugar substitutes.

The review did not suggest a link between sugar substitutes and cancer or other major adverse health effects. But the researchers noted that the evidence of safety was of low quality — meaning TKTK — and so more studies are also needed to rule out potential harms of non-sugar sweeteners.

Study limitations

In an editorial accompanying the review, Vasanti Malik, a research scientist at the Harvard T.H. Chan School of Public Health in Boston, who was not involved with the review, noted some limitations of the review. For example, some relatively long-term studies suggest sugar substitutes may help prevent weight gain, but these studies were not included in the current review because they did not specify a type of sugar substitute, Malik said. (Instead, these studies considered broader categories of "diet beverages" versus sugar-sweetened beverages.)

In addition, the health effects of sugar substitutes could differ depending on whether they are compared with "real" sugar or with water. But the new review did not differentiate studies based on the "comparator" (real sugar, water, etc.), and this may have affected the results, Malik said.

Malik agreed that the findings "highlight the need for larger and longer-term studies of NSS [non-sugar sweeteners] to guide policy development."

In July 2018, the American Heart Association published an advisory on low-calorie sweeteners that encouraged people to replace sugar-sweetened beverages and diet beverages with water. But the advisory also acknowledged that diet beverages may help wean people off sugar-sweetened beverages as they transition to water.

Originally published on Live Science.

Rachael Rettner

Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.