Alternate Sweeteners and Low Carb Diets – What You Need to Know (Updated)

Tempting isn’t it?

Many of us would love to have our low carb cake and eat it too, to be able to enjoy all the sweet foods our brain desires while still losing weight on a low carb diet. Artificial sweeteners seem to promise that we can have the cake and still heal our metabolism and lose weight. But is this true? Are artificial sweeteners a safe and healthy path to weight loss?

Until recently, research on artificial sweeteners has been lacking. Now there is a wealth of data and we are beginning to understand the impact these relatively new sweet processed products can have on our health.

To very briefly summarise the scientific literature, there are animal studies and long term observational human studies linking artificial sweetener use with adverse events including elevated insulin, impaired glucose tolerance, type 2 diabetes and weight gain. There is also some evidence that they can increase the risk of cardiac disease and adversely alter the gut microbiome. Concerns over previous decades linking artificial sweeteners to cancer have been largely disproved.

Are artificial sweeteners as harmful as eating lots of sugar? Almost certainly not.

But are they a completely risk-free sweet-loving loophole with no health consequences? Probably not.

Do artificial sweeteners have a place in your low carb real food diet? The answer (as is almost always the case in complex biological systems such as our human bodies) is… it depends.

Although they taste the same (or similar) to natural sugars, artificial sweeteners are processed with different metabolic routes and have different metabolic effects on blood sugar, insulin, weight gain, the gut microbiome and the reward system in the brain. As we are all different individuals, artificial sweeteners will affect us all differently. They may be very low in carbohydrates and calories, yet they can still have adverse effects.

For some people, the effects on the brain’s reward system make artificial sweeteners potentially harmful. They can wake up your inner sugar-craving monster (in Real Life Medicine, we call this monster ‘Fluffy’). This can be a very serious problem for many people. For some people, regular use of artificial sweeteners can slow down and even stop their weight loss on a low carb diet.

For some people, artificial sweeteners will have a greater effect on their metabolic health slowing or stopping weight loss, perhaps even promoting weight gain.

But it is not all doom and un-sweetened gloom. These sweet processed products can have a place in a low carb diet, but it is best if that place is not front and centre of all that you eat.

It is important to note too, that not all artificial sweeteners are created equal. At Real Life Medicine we lump artificial sweeteners into two main groups; the ‘least worst’ and the ‘worst worst’.

Least worst sweeteners

“Least worst” sweeteners have minimal effect on blood sugar and/or insulin levels. These include:

• Stevia – A natural plant extract, stevia is popular for its negligible impact on blood sugar and insulin. Some people notice a bitter aftertaste, but it is generally well tolerated.

• Monk Fruit Extract – Another natural option, monk fruit is very sweet and has little to no effect on blood sugar. It is often blended with other sweeteners to improve taste and texture.

• Erythritol – A sugar alcohol that is almost calorie-free and does not raise blood sugar or insulin. Some people experience digestive upset or a cooling sensation in the mouth.

• Xylitol – Another sugar alcohol, xylitol is low in carbs and has a minimal effect on blood sugar, but can cause digestive issues in some and is extremely toxic to pets.

• Allulose – A rare sugar that tastes remarkably like table sugar but is not metabolised by the body in the same way. Allulose does not raise blood sugar or insulin and may even have beneficial effects on blood sugar regulation and inflammation. Some people may experience digestive discomfort if consumed in large amounts, but it is generally well tolerated in moderation.

• Thaumatin – A natural protein sweetener derived from the katemfe fruit, thaumatin is intensely sweet, so only tiny amounts are needed. It does not impact blood sugar or insulin and is considered safe, with some research suggesting it may have anti-inflammatory properties. Its unique taste and higher cost may limit its use, but it is a promising option for those seeking a natural, low-carb sweetener.

Worst worst sweeteners

“Worst worst” sweeteners are those that cause (or are likely to cause) a rise in blood sugar and/or insulin. These include:

• Maltitol

• Isomalt

• Mannitol

• Acesulfame Potassium

• Aspartame

• Cyclamate

• Sorbitol

• Glycerol

• Saccharin

• Sucralose

• Neotame

• Advantame

• Maltodextrin

These sweeteners are best avoided, as they can undermine the benefits of a low carb lifestyle by raising blood sugar and insulin, and may also cause digestive upset.

In summary, it is best to minimise artificial sweeteners, as they can stall your weight loss goals in several ways. They can stimulate insulin and keep the "woodshed" of your fat stores closed. They are conducive to non-hungry eating. They can make up sugar cravings. It is very easy to eat a lot of food made with any sweeteners as they can override our normal hormonal hunger controls.

As we well know, eating a lot of low carb food means the carbs can add up, and you may no longer be low carb at all. However, for special occasions, alternate sweeteners from the “least worst” list can be a good alternative to standard sugary foods.

Updated: April 16, 2025