Artificial sweeteners may make you fat

In this Article (Index)

• Artificial Sweeteners
• How are Artificial Sweeteners made?
• Stevia is "Natural"
• Sugar-free sweeteners have an impact on the environment
• Synthetic Sweeteners and your health
• Adverse side-effects of artificial sweeteners
• Effects on unborn babies
• WHO's stark warning
• Negative impact on gut microbe

Artificial Sweeteners

Artificial sweeteners are man-made sugar substitutes, food additives that give foodstuffs and beverages a sweet taste with a lower (or nill) content of energy. They are therefore low-calorie or even zero-calorie sweeteners.

How are Artificial Sweeteners made?

Science also calls them Nonnutritive sweeteners (NNS). The first one to be synthesized was Saccharin. It was created by a chemist named Constantin Fahlberg, who obtained it from coal tar derivatives in 1879.

Sodium Cyclamate (banned in the US, but not in the EU) followed in 1937, Aspartame in 1965, Acesulfame Potassium (or Acesulfame K) in 1967, Sucralose in 1976, and Neotame in 1996.

All of the above mentioned artificial sweeteners are al synthetic products, manufactured by chemical processes in industrial facilities, and the U.S. Food and Drug Administrtion (FDA) considers them GRAS (Generally Regarded As Safe for consumption).

Only One Sugar Substitute is "Natural"

Then, there is Stevia, a "natural" zero-calorie sweetener, that is obtained from a South American plant. However, use of stevia leaves (which contain about 10% of sweetening stevioside and rebaudioside A) and crude stevia extracts are not considered GRAS by the FDA. Instead, the FDA classifies the refined, high-purity steviol glycosides extracted from the plant's leaves as GRAS (2).

So even though stevia is a plant, the sweetener is obtained by an industrial process: the steviol glycosides are extracted from the leaves with water, followed by an alcohol solvent and crystallization. Some brands add other chemicals such as erythritol (another low-calorie natural sugar) to their stevia.

Artificial sweeteners are found everywhere

Even if you don't deliberately consume them, you are exposed to them as sweeteners in some medications, in tooth paste, and mouthwash, for instance. They are used in diet sodas, sports drinks, low-sugar candies, fruit juices, flavored iced teas, and processed foods.

A Multibillion Industry

Synthetic sucralose is probably the most pervasive artificial sweetener (1) and is found in around 4,500 different types of foods, and accounts for 62% of the $1.15 billion global artificial sweetener market.

Sugar-free sweeteners have an impact on the environment

Despite being approved as safe for human use, their eco-toxicity is matter of debate.

These man-made chemicals (at least in theory) are not broken down by the human digestive system so they enter sewage unaltered (excreted in urine and feces).

They then enter wastewater treatment plants where the microbial digestors cannot break them down either, and are discharged in the treated water (or as raw sewage in developing countries) into the environment.

To make matters worse, Shaoli Li, et al. (2018) (3) found that the presence of artificial sweeteners "did inhibit microbial activity and microbial community structure" in the natural environment. And that a mix of different types of artificial sweeteners had a greater impact on them than individual ones.

Ace-k and sucralose can be found in concentrations levels of around 1 µg per liter in surface-waters and aquifers placing these concentrations of chemicals "among the highest known for anthropogenic trace pollutants." (4)

So we are discharging vast amounts of non-digested artificial sweeteners into our water supplies, where they are absorbed by fish, plants, insects, microbes, and crustaceans.

Synthetic Sweeteners and your health

Despite the fact that the FDA regards artificial sweeteners as GRAS, they aren't biologically inert. They are supposed to pass through your body without being digested (that is why they are low or zero calorie sweeteners: your body cannot obtain any energy from them as it can't break them down), but some recent evidence suggests otherwise.

Sucralose is stored in fatty tissue

A paper by Bornemann et al., (2018) (5) reported that sucralose can be metabolized in the gut of rats producing two fat-soluble or "lipophylic" compounds.

This differs from studies that were presented to the FDA to obtain its regulatory approval, which stated that sucralose was not broken down in the body, something which was reassuring, meaning that it could not be absorbed or metabolized.

This new study also disclosed that sucralose was detected in the rats' fatty tissue two weeks after the rats had stopped being fed sucralose, meaning that it stays inside the body, where its potential health effects are unknown.

Adverse side-effects of artificial sweeteners

Pepino (2010) (6) described how these supposedly "metabolically inactive" man-made sweeteners can upset the balance of human metabolism:

1. Artificial sweeteners interfere with the microbes that live in the gut.
2. They interact with sweet-taste receptors in the digestive system and this upsets insulin production, glucose control and the body's energy balance.

As a result this increases the "risk to develop obesity, metabolic syndrome, and type 2 diabetes."

A study with fruit flies and mice (Wang et al., 2016) (7) explored how artificial sweeteners upset metabolism to provoke increased appetite and sleep disruption:

The researchers fed fruit flies sucralose with their regular food (they ate the same amount of calories as usual), and found that those that ate this diet for a long period of time (for flies this was 5 days or more - which is equivalent to approx. 8 years for a human being) increased their intake of food and calories.

They concluded that "sucralose has an appetite stimulating effect" which made the flies consume 30 percent more calories when they were later given a naturally sweetened food.

Fortunately the effect is reversible: after 3 days of not eating sucralose their appetite returned to normal levels.

The study found that sucrose interacts with sweet taste neurons, which triggers the fly's insulin system and increases their appetite.

Additionally it "promotes hyperactivity, insomnia, and sleep fragmentation." This is because the combination of a sweet-taste that lacks calories, induces a "mild starvation or fasting state" that alters behaviour besides increasing hunger pangs.

They then tested mice (some ate sucralose sweetened jelly and the others none), those eating sucralose "showed a significant increase in food intake."

Negative impact on gut microbes

Gut microbes can keep us in good health by taking part in our digestive process (fermentation food), assisting in the development of immune cells, regulating the intestinal nervous system, and blocking intestinal colonization by pathogens. The balance of the up to 1,000 microbial species in our intestines is therefore critical for good health.

According to Wang et al., (2018) (2) consuming artificial sweeteners "alters the relative proportion of intestinal microbial phyla" this is due to the sweetener's bacteriostatic effect (they stop bacteria from reproducing or growing):

"Synthetic sweeteners acesulfame potassium, saccharin and sucralose all exerted strong bacteriostatic effects... [and] rebaudioside A, the active ingredient in the natural [artificial sweetener] stevia, also had similar bacteriostatic properties."

In mice, sucralose increased the quantity of a strain of bacteria called Firmicutes, which is also found in obese mice but not in their lean littermates.

Abbot et al., (2014) (8) reported that the gut microbiome disruption caused by artificial sweeteners may be the cause behind metabolic disease.

They studied mice, feeding them with different synthetic sweeterners and after 11 weeks the animals had glucose intolerance.

They fed different groups of mice with different diets; some ate a normal diet, others a high-fat one, and their water was spiked either with glucose or glucose plus saccharin.

The mice drinking saccharin spiked water had a higher glucose intolerance compared to the group that only drank water with glucose.

Saccharin altered the gut microbes to cause glucose intolerance!

The scientists also transplanted faecal matter from glucose-intolerant saccharin fed mice into the intestines of mice which had been bred to have sterile gut, and as expected the transplanted bacteria colonized their hosts' intestines and made them glucose intolerant.

When the mice were given antibiotics to kill the microbiome, glucose intolerance was prevented.

Effects on unborn babies

Moriconi et al., (2020) (9) pointed out animal studies showing that sweeteners can cross the placenta during pregnancy and provoke a prenatal exposure to them. This "early prenatal exposure to specific non-calorie sweeteners could favor the occurrence of metabolic diseases later in life, by inducing detrimental changes in the gut microbiota composition."

Daily intake levels

The FDA (10) sets a maximum "acceptable daily intake" level for each of the approved sweeteners.

This level is based on the available scientific evidence and according to the FDA makes these "high-intensity sweeteners ... safe for the general population under certain conditions of use."

Nevertheless, back in 1998, the American Dietetic Association stated that artificial sweeteners should not be used in children younger than 2 years of age and minimal or totally restricted during pregnancy and lactation (11).

The WHO's stark warning

In May 2023, the World Health Organization (WHO) released a new guideline on non-sugar sweeteners (NSS) (12).

In these guidelines the WHO recommends not using non-sugar sweeteners to control body weight. These guidelines suggest that the use of NSS does not ensure any long-term benefit in reducing body fat in adults or children. Furthermore, it found negative long term effects from using these sweeteners include an increased risk of type 2 diabetes, cardiovascular diseases, and mortality in adults.
This recommendation does not apply to people suffering from pre-existing diabetes. It covers all synthetic and natural non-nutritive sweeteners (so it includes stevia).

The systematic review found no evidence of long-term benefit on measures of body fatness in adults or children, and potential undesirable effects from long-term use in the form of increased risk of type 2 diabetes, CVDs and mortality in adults. Limited evidence suggests potential undesirable effects in the form of increased risk of preterm birth with NSS use during pregnancy (WHO

A word of caution

This report has been criticised because it relies heavily on observational studies and no so much on clinical trials, the former would notice that obese or overweight people use sweeteners and conclude that those who use them tend to be overweight, while in fact they are using them to lose weight, a phenomenon called "reverse casuality." Clinical trials on the other hand are much better at establishing cause-effect links.

We should wait for further studies with large cohorts of participants before reaching ditching sweeteners.

Conclusion: Not so sweet is it?

These studies reveal that sugar-free sweeteners are not inert, and that they have a metabolic effect; they interact with your body.

They upset the balance of the microbes in your gut, which has an impact on your overall health, an impact which is still being studied.

Artificial sweeteners make you hungry and make you eat more; it increases your glucose intolerance and this tends to cause obesity.

On the other hand, natural sugars have the drawback of being energy rich.
Far worse are the "added sugars" found in most processed foods and beverages (read our blogpost: Sugar: the poison added to our food).

For this reason a zero calorie sweetener option is good if you are trying to lose weight: you can use artificial sweeteners to cut out the unnecessary sugary calories and help you on your weight loss program.