Do artificial sweeteners cause weight gain? A closer look at the evidence

We’ve all been there — staring longingly at a dessert menu while mentally calculating the calorie damage, only to settle for a “zero-calorie” diet soda to balance the scales. But are these artificially sweetened saviours helping us lose weight, or quietly nudging the number on the scale upwards?

The relationship between artificial sweeteners and weight gain is more complicated than the back of a sweetener packet suggests, and it’s one that’s attracted a fair bit of controversy in clinical studies.

Artificial sweeteners fall into a category known as non-nutritive sweeteners. Some researchers argue that non-nutritive sweeteners support weight management by reducing calorie intake and sugar dependence [1]. Others warn that consuming artificial sweeteners might confuse your sweet taste receptors, increase food reward cravings, and lead to higher body mass index (BMI) over time [2].

With the obesity epidemic, metabolic syndrome, and cardiovascular disease on the rise, it’s worth examining whether these sugar substitutes are the solution or part of the problem.

What are artificial sweeteners?

Artificial sweeteners (also called non-nutritive or low-calorie sweeteners) are food additives used to sweeten foods and sugary drinks without the added calories of sugar. These compounds are many times sweeter than regular sugar, which means only a tiny amount is needed to satisfy your sweet tooth. They’re commonly found in diet sodas, artificially sweetened beverages, sugar-free gum, and “lite” versions of your favourite snacks [3].

Originally developed to help people with diabetes manage blood sugar, artificial sweeteners have since become a go-to tool for those looking to reduce sugar intake or lose weight.

But while they may offer fewer calories, their impact on body weight, metabolic health, and energy intake isn’t entirely straightforward. Some studies suggest that they may help control calorie intake, while others have linked artificially sweetened drinks with increased consumption and (paradoxically) weight gain [1].

Types of artificial sweeteners

Artificial sweeteners come in several varieties, each with a different chemical makeup and level of sweetness. Here's a closer look at the most common types:

• Aspartame: Often used in diet sodas like Diet Coke; about 200 times sweeter than sugar [4]
• Saccharin: One of the earliest sugar substitutes; found in tabletop sweeteners and some toothpaste
• Sucralose: The active ingredient in Splenda; heat-stable and popular in baking
• Acesulfame potassium (Ace-K): Commonly blended with other sweeteners; used in drinks and protein powders
• Stevia: A plant-derived option with zero calories; popular among those seeking more “natural” sugar substitutes
• Sugar alcohols (like xylitol and erythritol): Often used in chewing gum and low-carb treats; may cause stomach upset in large amounts [5]

Which artificial sweeteners should you avoid?

While all artificial sweeteners used in the UK have been deemed safe by food regulatory authorities (within the acceptable daily intake limits), that doesn’t mean they all play nicely with your gut or your goals [6].

Some sweeteners, like saccharin and Ace-K, have come under fire in certain clinical studies for their potential effects on insulin sensitivity, gut microbiota, and even increased risk of health problems like bladder cancer, though evidence in humans remains limited and controversial [7].

What’s clear is this: not all sugar substitutes are created equal. 

If you’re looking to manage weight, reduce sugar intake, or protect your metabolic health, it’s worth paying attention to how different sweeteners affect your appetite, digestion, and overall energy intake [8]. That might mean skipping the diet beverages in favour of naturally flavoured sparkling water or sticking to whole foods that don’t need a chemical compound to sweeten the deal.

Benefits of using artificial sweeteners

Let’s start with the sweet stuff. Artificial sweeteners were originally hailed as a breakthrough for people managing diabetes, and for good reason; they offer the sweet taste of sugar without the accompanying blood sugar rollercoaster. Because these sweeteners contain little to no calories, they can help reduce calorie intake and support weight management goals when used in moderation. They’ve also become a popular tool in reduced-calorie diets, offering a psychological win when you're trying to lose weight without feeling like you're living on air and celery [8].

Research from various randomised controlled trials has shown that replacing sugar-sweetened beverages with artificially sweetened drinks may result in modest reductions in body weight, fat mass, and even waist circumference — provided other healthy habits are in place [9]. Think of them as a dietary training wheel: they might help you wean off the sweet stuff while gradually shifting towards less processed, whole foods.

Plus, for people with weight-related health problems like heart disease, high blood pressure, or type 2 diabetes, swapping sugar for non-nutritive sweeteners might offer tangible health benefits.

Risks of using artificial sweeteners

Now for the not-so-sweet truth. While they may seem like a miracle fix, artificial sweeteners aren’t without their potential pitfalls. Some clinical studies have linked artificially sweetened beverages with increased consumption overall — think of it as the “I had a Diet Coke, so now I deserve fries” effect [1].

There's also some concern that frequent exposure to high-intensity sweeteners may confuse your sweet taste receptors, making naturally sweet foods like fruit taste bland and leading to increased cravings for intensely sweet, calorie-dense foods. In the long term, this could work against your weight control goals.

Beyond cravings, emerging research has explored potential links between artificial sweeteners and changes in the gut microbiome, insulin sensitivity, and even associations with higher body mass index.  While the science is far from settled (and often muddied by other factors like overall diet and physical activity), it’s clear that artificially sweetened doesn’t always mean risk-free [9].

Moderation is still key, and choosing whole foods over sugar substitutes remains the gold standard for both weight loss and long-term metabolic health.

Can artificial sweeteners make you put on weight?

It’s the million-sachet question — and the answer is, well, complicated.

While artificial sweeteners contain fewer calories and don’t spike blood sugar like table sugar, some studies suggest that consuming artificial sweeteners may lead to increased food intake later on, thanks to changes in appetite signalling and sweet taste receptors playing tricks on your brain.

The theory? Your body registers sweet taste but doesn’t receive the energy it expected, leading it to go sniffing around for calories elsewhere [2]. That said, this isn't a guarantee you'll gain weight — it depends on other factors like what you're eating overall, how active you are, and whether you're downing diet soda alongside three pastries.

Metabolic pathways of sugar vs. artificial sweeteners

Here’s where it gets geeky (but stay with us): sugar, when consumed, is rapidly broken down into glucose, raising blood sugar and triggering insulin release. Over time, high intake can lead to insulin resistance, increased risk of heart disease, and a whole host of metabolic health issues [10].

Artificial sweeteners, on the other hand, don’t follow the same metabolic pathway. Most are not metabolised at all — they simply pass through the digestive system without contributing to energy intake or triggering insulin in the same way. That’s part of why they’re often marketed as a clever shortcut to manage weight and support weight loss.

Which is worse: Sugar or artificial sweeteners?

If you’re choosing between the two, sugar is the clear frontrunner for metabolic mischief.

Excess sugar intake (especially in the form of sugar-sweetened beverages and added sugars) has been directly linked to weight gain, cardiovascular disease, type 2 diabetes, and more.

Artificial sweeteners, while not perfect, generally offer a way to reduce overall calorie intake and lose weight, particularly when paired with healthy habits [2].

So if you’re weighing up sweetened beverages at the supermarket, the artificially sweetened option might just be the lesser evil (just don’t treat it like a hall pass to the snack aisle).

Do artificial sweeteners mess up your metabolism?

As we've explored above, the current scientific consensus is neither a yes nor a no. What we do know is that relying on highly processed sugar substitutes without addressing whole foods, physical activity, or weight-related health problems probably won’t move the needle in your weight management journey.

That’s why the Juniper Programme takes a whole-person approach. It’s not just about the calorie sweeteners. It’s about understanding your metabolism, working with a licensed healthcare professional, and making sustainable changes that support long-term weight loss.

Whether you’re sweetening your tea or skipping it altogether, the best results come from having a plan tailored to your biology, not just your taste buds.

Take the guesswork out of what to eat with Juniper

The Juniper Programme combines weight loss medication with dietitian-led health coaching and tracking, so you can lose weight and reach your goals for good.

Kickstart your weight loss journey with Wegovy or Mounjaro, two groundbreaking weight loss medications that mimic the GLP-1 and GIP hormones, respectively, to help control cravings, delay stomach emptying, and keep you feeling fuller for longer. These clinically backed treatments help members experience up to 23% body weight loss.

Plus, we have a team of expert dietitians and health coaches you can consult with to help you work through any challenges you're experiencing during your weight management journey. This approach sets you up for sustained weight loss, rather than a quick-fix solution.

This means you can continue to enjoy the things you love in moderation without ever feeling deprived.

Ready to see if Juniper is right for you? You can check your eligibility here.

Image credit: Pexels