How Do Artificial Sweeteners Influence Weight?

Artificial sweeteners are very commonly consumed throughout the general population and also appear to be very popular among people who have eating disorders. Paradoxically, there is new evidence to suggest that consuming artificial sweeteners is associated with weight gain. That might be expected if people at risk for or experiencing weight gain are more likely to use artificial sweeteners. However, a recent study suggests that other mechanisms may be at work.

In a recently-published article in the journal Nature, Dr. JothamSuez and colleagues examined the impact of artificial sweeteners on intestinal bacteria (the microbiome), both in laboratory animals and in people (Nature 2014; doi: 109.1038\nature13793). In humans, the microbiome consists of more than 100 trillion bacteria that live in our gut, mouth, and skin. The role these bacteria play in health and illness is only now beginning to be understood.

The researchers described a series of studies. First, mice were provided with water containing artificial sweetener (saccharin) or sugar water. Saccharin consumption quickly changed the bacterial species found in the gut, and higher percentages of bacteria were associated with weight gain and predisposition to type 2 diabetes. These mice also developed glucose intolerance. Antibiotic treatment blocked the effects, and transferring fecal material from affected mice to those never exposed to saccharin transferred the glucose intolerance as well.

Subsequently, the investigators did two experiments involving humans. First, they studied 381 people who were divided into two groups: those who consumed large amounts of artificial sweeteners and non-consumers of artificial sweeteners. Blood sugar control was poorer in those who consumed high amounts of artificial sweeteners, and there were substantial differences in the types of bacteria found in the guts of the two groups. A second experiment involved 7 people who did not consume artificial sweeteners. For one week this group consumed the maximum acceptable daily intake of saccharin. At the end of just 7 days of exposure to artificial sweeteners, measures of blood sugar response had changed, and gut bacteria changed over that period of time as well.

In 2012, the American Heart Association and the American Diabetes Association issued a joint statement on the use and health perspectives of nonnutritive sweeteners (Diabetes Care 2012; 35:1798). The two groups reviewed consumer attitudes, patterns of consumption, appetite, body weight, hunger and energy intake, and components of the cardiometabolic syndrome. This syndrome causes a multitude of maladaptive cardiovascular, renal, metabolic, prothrombotic, and inflammatory abnormalities, leading to a substantial increase in premature cardiovascular disease disease and stroke. The statement they subsequently issued focused on 6 nonnutritive sweeteners: aspartame (Equal®, Nutrasweet®), acesulfame-K (Sunette®, Sweet One®), neotame (no brand names), saccharin (Sweet’N Low®, Necta Sweet®), and sucralose (Splenda®), all food additives regulated by the US Food and Drug Administration. A more recently discovered product, the low-calorie natural sweetener, stevia, has not been determined by the FDA to be a safe product; no objection letters have been filed for stevia thus far.

After their research, the two organizations stated that there are still not enough data to determine conclusively whether the nonnutritive sweeteners in beverages and foods reduce added sugars or carbohydrate intakes or have any beneficial effects on appetite, energy balance, body weight, or cardiometabolic risk factors. They concluded that when used judiciously, nonnutritive sweeteners could help reduce added sugar intake, thereby resulting in decreased total energy and weight loss/weight control, and promoting beneficial effects on related metabolic parameters. However, they added, “these potential benefits will not be fully realized if there is a compensatory increase in energy intake from other sources.”

Long-term studies show that regularly consuming artificially sweetened beverages reduces the intake of calories and helps promote weight loss or maintaining weight loss, but other studies show no effect and others even show weight gain (Eur J Clin Nutr 2007; 61:691). A recent meta-analysis of 15 randomized controlled trials and 9 prospective cohort studies of low-calorie sweeteners and body weight and composition showed that substituting low-calorie sweeteners for sugar resulted in modest weight loss and may be a useful dietary tool to improve compliance with weight loss programs or to maintain weight loss (Am J Clin Nutr 2014; 100:765).

The results of Suez and colleagues’ work have arrived quite early in the process of our increasing understanding of the relationship between food intake, gut bacteria, and weight, and far more research is needed. Nonetheless, their work raises very interesting questions about artificial sweeteners, and highlights the potential importance of food intake in modifying the body’s responses in terms of weight and blood sugar. Further studies involving the microbiome will likely be highly informative for eating disorders as well as obesity.