The ketogenic or “keto” diet has gained traction in recent years as a weight loss tool. It involves eating very few carbs, moderate amounts of protein, and high amounts of fat (1).

By depleting your body of carbs, the keto diet induces ketosis, a metabolic state in which your body burns fat for fuel instead of carbs (1).

Staying in ketosis can be challenging, and some people turn to artificial sweeteners like aspartame to help keep their carb intake low.

However, you may wonder whether using aspartame affects ketosis.

This article explains what aspartame is, describes its effects on ketosis, and lists its potential downsides.

Aspartame is a low-calorie artificial sweetener that’s widely used in diet sodas, sugar-free gum, and other food products. It’s created by fusing two amino acids — phenylalanine and aspartic acid (2).

Your body naturally produces aspartic acid, whereas phenylalanine comes from food.

Aspartame is a very sweet sugar substitute with 4 calories per 1-gram serving packet. Sold under several brand names, including NutraSweet and Equal, it’s generally considered safe for consumption (2, 3, 4).

The Food and Drug Administration (FDA) defines the Acceptable Daily Intake (ADI) for aspartame to be 23 mg per pound (50 mg per kg) of body weight (3).

Meanwhile, the European Food Safety Authority (EFSA) has defined the ADI to be 18 mg per pound (40 mg per kg) of body weight (3).

For context, a 12-ounce (350-ml) can of diet soda contains about 180 mg of aspartame. This means a 175-pound (80-kg) person would have to drink 23 cans of diet soda to surpass the FDA’s limit for aspartame — or 18 cans by EFSA’s standards.


Aspartame is a low-calorie sweetener that’s generally considered safe for consumption. It’s widely used in diet sodas, sugar-free gum, and many other food products.

To achieve ketosis and maintain it, your body needs to be depleted of carbs.

If enough carbs are added back into your diet, you’ll exit ketosis and return to burning carbs for fuel.

Most keto diets limit carbs to about 5–10% of your daily calorie intake. On a diet of 2,000 calories per day, this equates to 20–50 grams of carbs per day (5).

Aspartame provides less than 1 gram of carbs per 1-gram serving packet (4).

Studies have found that it does not increase your blood sugar levels. One study in 100 people found that consuming aspartame twice weekly for 12 weeks had no effect on participants’ blood sugar levels, body weight, or appetite (1, 5, 6, 7).

Furthermore, given that it’s quite sweet — up to 200 times sweeter than table sugar — you’re likely to consume it in modest amounts (1).


Aspartame provides very few carbs and thus does not increase your blood sugar levels when consumed in safe amounts.

As aspartame does not increase your blood sugar levels, it likely won’t cause your body to exit ketosis (5, 6, 7).

In one study, 31 people followed the Spanish Ketogenic Mediterranean diet, a type of keto diet that incorporates a lot of olive oil and fish. They were allowed to use artificial sweeteners, including aspartame (8).

After 12 weeks, participants had lost an average of 32 pounds (14.4 kg), and their blood sugar levels had decreased by an average of 16.5 milligrams per deciliter. Most notably, the use of aspartame did not affect ketosis (8).


Given that aspartame does not increase your blood sugar levels, it likely won’t affect ketosis when consumed in moderate amounts.

Aspartame’s effects on ketosis have not been studied specifically, and the long-term effects of keto diets — with or without aspartame — are unknown (5).

While this sweetener is generally considered safe in most people, there are some considerations to keep in mind.

People who have phenylketonuria should not consume aspartame, as it can be toxic. Phenylketonuria is a genetic condition in which your body cannot process the amino acid phenylalanine — one of the main components of aspartame (3, 9).

Additionally, those who take certain medications for schizophrenia should steer clear of aspartame, as the phenylalanine in the sweetener may worsen potential side effects, potentially affecting muscle control (10).

Furthermore, some feel that it’s unsafe to consume any amount of this sweetener. However, this has not been well studied. More research on using aspartame while following a keto diet is needed (2, 3).

If you consume aspartame while on a keto diet, make sure to do so in moderation to stay within the allowed number of carbs that will keep you in ketosis.


Aspartame is generally considered safe, but it should be consumed in modest amounts to keep you in ketosis. More research on the direct effects of aspartame on ketosis is needed.

Aspartame can be useful on the keto diet, adding some sweetness to your food while providing only 1 gram of carbs per 1-gram serving packet.

As it doesn’t raise your blood sugar, it likely won’t affect ketosis.

While aspartame is generally considered safe for most people, its use on a keto diet has not been studied thoroughly.

Thus, you should be sure to stay below the Acceptable Daily Intake and use aspartame modestly to help maintain your keto diet.