Are artificial sweeteners worse for you than sugar?

This headline might surprise you.

For decades, we've been sold artificial sweeteners as a harmless, no-calorie alternative to sugar, good for weight loss and maintaining steady blood sugars.

But is this really the case?

Mounting research finds that artificial sweeteners are not the benign substance we once thought.

Let's take a look.

What are sweeteners?

Artificial sweeteners are synthetic compounds designed to mimic the sweetness of sugar without the associated calories.

They are widely used in the UK food manufacture to reduce the sugar in foods and drinks while keeping them sweet.

Common types include sucralose (found in Splenda), aspartame (Canderel, Hermesetas), and acesulfame potassium (Hermesetas Gold).

These types are all found in sugar-free drinks like 'zero' fizzy drinks and 'no added sugar' squashes and foods like yogurt, baked beans and jelly.

Natural sweeteners (e.g. stevia) and sugar alcohols (e.g. xylitol, erythritol, and sorbitol) are also used to sweeten food and drinks – they're generally considered to be better for you compared with artificial sweeteners, and I'll talk about them another time.

So, in this post, I focus specifically on artificial sweeteners. 

Artificial sweeteners and their impact on the gut microbiome

One of the most concerning, and well established, findings about artificial sweeteners is their potential to disrupt the gut microbiome.

A landmark study in 2014 showed that artificial sweeteners like saccharin and sucralose can disrupt gut bacteria, and in some people can lead to glucose intolerance, meaning the body becomes less efficient at handling sugar.

Studies since 2014 have confirmed this link (although it should be noted that there's also lots of studies that didn't find a link).

There’s also emerging research (mostly from animal and in vitro models; limited human studies; this 2025 review is useful) suggesting that artificial sweeteners may affect the gut lining itself, increasing what’s called ‘leaky gut', where inflammatory compounds leak into the bloodstream.

More human research is clearly needed, but this could be another way they influence long-term metabolic health.

Artificial sweeteners and their impact on blood sugar regulation

Artificial sweeteners were originally developed to help with blood sugar control, especially for people with diabetes.

So evidence suggesting that in some cases they may impair rather than improve glucose regulation, is rather concerning.

For example, a well known study from Yale in 2020 found that combining sucralose with carbohydrates worsened insulin sensitivity in humans.

A 2024 review concludes that sucralose has been associated with elevated insulin levels and reduced insulin sensitivity, possibly through both metabolic and microbiome-related mechanisms, although it finds that results vary from study to study.

Artificial sweeteners and their impact on hunger

Given one of the major reasons to avoid sugar is to reduce calories, it may surprise you to know that there's now evidence so suggest that artificial sweeteners make you more hungry.

A 2025 study published in Nature Metabolism found that sucralose increased blood sugar to the hypothalamus (the part of the brain responsible for hunger) more than sugar did.

This heightened activity was associated with increased feelings of hunger.

The mechanisms by which sweeteners influence appetite are complex and not fully understood.

Increased appetite could be due to the brain's expectation of caloric intake following the sweet taste: the brain is expecting food (calories) and when it doesn't get it from artificial sweeteners (calorie free), this mismatch can lead to heightened hunger signals.

Artificial sweeteners and their impact on metabolic health

Artificial sweeteners have been found to increase incidence of weight gain, type 2 diabetes and high blood pressure, several meta-analyses show (2017, all 3; 2015, diabetes; 2015, blood pressure).

Artificial sweeteners and cancer risk

Aspartame, one of the most widely used sweeteners, was classified by the World Health Organization in 2023 as “possibly carcinogenic to humans” based on limited evidence for liver cancer.

However, the overall risk at normal consumption levels is still debated, and regulatory bodies continue to set safe daily intake limits.

While this doesn’t mean aspartame is proven to cause cancer, it adds another reason to be cautious about regular use.

Some balance

It's important (but possibly not helpful) to know that not all research paints artificial sweeteners in the same negative light.

A very recent 2025 review published in Frontiers in Nutrition looked specifically at people with diabetes and concluded that sweeteners like aspartame and sucralose can sometimes support glycemic control, reduce calorie intake, and help manage weight.

However, the authors caution that sweeteners may still affect the gut microbiome and that their long-term effects are not fully understood.

Yes, nutrition science is complex and often contradictory.

In conclusion

I can't give you a definite answer to the question in the headline.

But, just because artificial sweeteners don’t contain calories doesn’t mean they’re inert.

The science is still evolving, but what’s clear is that these chemicals can influence our gut, our metabolism, and even our brains.

That’s why focusing on real, whole foods – rather than chasing the next ‘sugar-free’ fix – is probably the safest bet for long-term health.

Concerned about your health and nutrition and need some guidance?

Get in touch if you’d like personalised guidance to help you take charge of your health.

Contact me

Disclaimer

The information and advice I provided here is of a general nature and should never replace individual health or medical advice provided by your doctor or other healthcare professional involved in your care.