It is not clear if aspartame helps people lose weight, as it may also increase appetite and affect a person’s metabolism. Aspartame may also have other negative health effects and be unsafe for some people.

Aspartame is an artificial sweetener and a popular sugar substitute. It is present in low-calorie food and drinks and some medications.

It is available in the United States under the brand names Nutrasweet and Equal and is an ingredient in many soft drinks and food items.

Despite its extensive use and popularity, aspartame has become a source of controversy in recent years, with several studies claiming the sweetener has adverse health effects.

In this article, we look at the current evidence on the safety of aspartame. We also investigate how it might affect weight, appetite, and certain medical conditions.

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The U.S. Food and Drug Administration (FDA) approved aspartame for use in food and drink in 1981. According to the FDA, over 100 studies have shown aspartame to be safe for most people.

Agencies in Europe, Canada, and many other countries also approve its use, including:

  • European Food Safety Authority (EFSA)
  • Health Canada
  • Food and Agriculture Organization of the United Nations
  • World Health Organization (WHO)

According to the International Food Information Council, the FDA has set an acceptable daily intake (ADI) for aspartame of 50 milligrams per kilogram (mg/kg) of body weight per day. The EFSA has set a lower ADI of 40 mg/kg per day.

Most people will not reach these ADI amounts. If a person weighs 68 kg, they would need to drink around 19 cans of soda or consume over 85 packs of aspartame every day to exceed the ADI.

People who eat and drink products containing aspartame consume around 4.9 mg/kg a day on average, which is less than 10% of the FDA’s recommended ADI.

Aspartame may have the following side effects:

Effects on body weight

Aspartame contains 4 calories per gram (g), which is a similar amount to sugar, but aspartame is around 200 times sweeter than sugar. This means that only a tiny amount of aspartame is necessary to sweeten foods and drinks. For this reason, people often use it in weight loss diets.

However, a 2017 review of studies found no evidence that the low-calorie sweeteners aspartame, sucralose, and stevioside were effective for weight management.

Studies in the review monitored participants over several years. Researchers found a link between increased body weight and waist circumference and a regular intake of these sweeteners.

Participants in some studies in the review showed an increased body weight.

The 2017 review also found evidence that suggested those who consume sweeteners regularly might be at greater risk of developing heart disease, diabetes, and stroke.

Effects on appetite

Some research suggests that aspartame may affect body weight by increasing people’s appetite, which can lead to greater food consumption.

For example, a 2015 animal study found that aspartame increased appetite in rats. The review suggested that sweeteners may raise appetite by disrupting the signaling process that usually occurs when a person eats foods with more calories.

Artificial sweeteners such as aspartame provide sweetness without providing the body with energy, and this effect on the body may stimulate appetite.

Sweet tastes typically signal to the body that food is entering the gut. The body then expects to receive calories and signals when eating should stop by making a person feel full or satiated.

A person experiences the same sweet taste when they consume sweeteners, but the body receives fewer calories than it might otherwise expect.

If this happens regularly, according to the theory, the body unlearns the association between sweet tastes and calories. This reversal means that high-calorie foods will no longer trigger feelings of fullness. This can lead to overeating.

Certain amino acids in aspartame, such as phenylalanine, may also have an effect on appetite.

Other research does not support these findings, though. A 2018 study looked at aspartame intake in 100 lean adults with a BMI of between 18 and 25 who were between the ages of 18 and 60 years.

Researchers found that aspartame intake over the course of 12 weeks had no negative effects on appetite, body weight, or blood sugar management.

Further research on human participants might lead to a better understanding of the link between aspartame consumption and appetite control.

Effects on metabolism

A 2015 study found that high levels of aspartame may cause other changes in the body, such as changes in serum and oxidative stress markers, and can lead to type 2 diabetes in rats.

A later review from 2016 further discussed the link between low-calorie sweeteners and metabolic disease. It suggested that regular, long-term intake of sweeteners may disrupt the balance and diversity of bacteria living within the gut.

Animal studies show that this type of disruption can result in glucose intolerance, which is a known risk factor for type 2 diabetes.

Another study from 2016 investigated the effects of certain sugars and sweeteners on people’s glucose tolerance.

Researchers found a link between aspartame use and greater glucose intolerance among those with obesity. None of the sugars and sweeteners in the study had any negative effect on people with a healthy weight, though.

These studies suggest that regular intake of aspartame could increase the risk of glucose intolerance, particularly in people who may already be overweight.

The health risks of aspartame can affect a person short-term or long-term.

Short-term effects

A 2019 study looked at the short-term effects of aspartame on the blood and biochemical measurements in female Swiss albino mice over the course of 30 days.

The study found that consuming aspartame was harmful to the mice and produced negative effects relating to the blood and biochemical measurements. Researchers need further evidence and human studies to support these findings.

Long-term effects

There have been some concerns about the effects of aspartame on the central and peripheral nervous systems. A 2016 study looked at the long-term effects of aspartame on the sciatic nerve in 30 adult male albino rats.

Researchers gave one group of rats a dosage of aspartame equivalent to the ADI for humans of 40–50 mg/kg per day for 3 months.

The study found that long-term dosage of aspartame was harmful to the structure of the sciatic nerve, and stopping any intake of aspartame for a month did not lead to complete recovery.

Human studies may help scientists find out more about the effects of aspartame on nerve structure and function.

Some research suggests that aspartame increases the risk of:

A report from the U.S. Department of Health and Human Services assessed a number of studies looking at the potential risks of aspartame.

The report suggests a possible link between aspartame and some hematopoietic cancers in males, although researchers require further evidence from human studies.

Limited evidence exists showing a potential risk between aspartame and preterm delivery, so there is no clear conclusion on aspartame consumption and headaches.

The report concluded that there were no significant safety concerns for aspartame consumption at the ADI of 40 mg/kg.

There appears to be no scientific evidence that aspartame poisoning is a risk. If people have a condition called phenylketonuria (PKU), high levels of aspartame may be toxic for them. This is because aspartame contains an amino acid called phenylalanine.

People with phenylketonuria have a rare genetic disorder that means they cannot break down phenylalanine properly. If too much phenylalanine accumulates in people with PKU, it can be toxic to the brain and cause intellectual disability.

People with the following conditions should avoid aspartame:


Phenylketonuria (PKU) is a genetic metabolic disorder that increases levels of the essential amino acid known as phenylalanine in the blood. People with PKU are unable to metabolize phenylalanine properly, so they will need to avoid or limit their intake of it.

Phenylalanine is one of two amino acids that make up aspartame. Aspartame provides significantly lower amounts of phenylalanine than everyday food sources, such as meat, fish, eggs, and dairy products.

People with PKU need to monitor all dietary sources of phenylalanine to avoid toxic levels. As a result, all products containing phenylalanine in the U.S. carry a label.

Tardive dyskinesia

Tardive dyskinesia (TD) is a neurological disorder that causes sudden, uncontrollable jerking movements of the face and body. According to a 2017 review, TD most often results from long-term use of antipsychotic medications.

The review notes that some evidence suggests a link between a build-up of phenylalanine in the body and TD.

Many foods and drinks that carry the label “sugar-free” may contain some form of artificial sweetener.

The following could contain aspartame:

  • diet soda
  • low-sugar juices
  • flavored water
  • low-fat yogurt
  • low-fat flavored milk
  • nutrition bars
  • sugar-free puddings
  • gelatins
  • low-fat or light ice cream and popsicles
  • low-calorie tabletop sweeteners, such as Equal
  • some prescription and over-the-counter medicines, including chewable vitamins

Those wishing to limit their intake of aspartame may want to try an alternative natural sweetener, such as:

  • honey
  • maple syrup
  • agave nectar
  • stevia leaves
  • molasses

It is still important to limit intake of natural sweeteners, as they have the same health risks as excess refined sugar, such as weight gain, diabetes, and tooth decay.

There is still much controversy surrounding the safety of aspartame, despite approval from authorities around the world.

Some evidence suggests aspartame may have a negative impact on health, such as weight management, and potential risk for preterm delivery and specific cancers. Researchers require further studies in humans to support these findings.

For those with obesity, regular consumption of low-calorie sweeteners may increase the risk of metabolic diseases, including type 2 diabetes. People with certain conditions, such as PKU or TD, may need to avoid aspartame.

Organizations such as the FDA have approved aspartame as safe for human consumption within a certain daily limit.