'Healthy' protein bars are hiding as much sugar as a chocolate bar
Some 'healthy' protein bars contain nearly as much sugar as a chocolate bar. Here's what a major UK study found, and how to check any bar's label in seconds.
If you’ve swapped your afternoon chocolate bar for a “healthy” protein bar, you might not be cutting sugar at all. New analysis of hidden sugar in protein bars across the UK has found that many products marketed as nutritious snacks contain sugar levels that rival, or beat, an actual chocolate bar. The research, from Action on Salt and Sugar at Queen Mary University of London (QMUL), analysed more than 450 snack and protein bars sold in the UK’s biggest supermarkets, and the results suggest “protein,” “natural” and “high-fibre” labels tell you almost nothing about how much sugar is inside.
This isn’t a fringe finding from one supermarket aisle. It’s a pattern across a UK protein bar category that has grown rapidly as more people reach for a bar instead of a proper meal. Here’s what the research found, which real products it named, why the labelling loophole exists, and how to check any bar yourself in the time it takes to read the back of the wrapper.
What the Action on Salt and Sugar study actually found
Action on Salt and Sugar, a research group based at Queen Mary University of London, published its Snack Bars Report in November 2025 to mark Sugar Awareness Week. Researchers analysed 458 bars, spanning cereal bars, flapjacks and protein bars, sold across 10 of the UK’s largest supermarkets.
The topline numbers are stark. Under the UK’s voluntary traffic-light front-of-pack labelling system, 37% of the bars would carry a “high in sugar” red label. Measured against Chile’s stricter front-of-pack warning system, which many nutrition researchers consider a tougher benchmark, that figure rises to 68%, meaning roughly seven in ten bars would be flagged for excess sugar. Under the UK Government’s own Nutrient Profiling Model (the formula used to decide what can and can’t be marketed to children), 64% of the bars analysed would be classed as “less healthy”, despite the vast majority being sold and marketed as exactly the opposite.
Bars in the study averaged 175 kcal and 7g of sugar per serving, around a third of a 7-10-year-old’s maximum recommended daily intake of free sugars, in a single snack. Over half (55%) were also high in saturated fat. Perhaps most telling: among bars carrying a “high fibre” claim, roughly a third were still high in sugar, showing that one healthy-sounding claim doesn’t rule out another less healthy trait sitting right next to it on the label.
Dr Kawther Hashem, who worked on the research, put it plainly: “Parents are being misled into believing these products are healthy when many contain excess sugar and calories.”
Real products, real numbers: how “healthy” bars stack up
To be clear from the outset: none of the products named below are being singled out as unsafe or “bad.” They’re simply the examples the study’s own published figures identify, presented here so you can compare them against what you’d expect from a chocolate bar, and decide for yourself what fits your diet.
The study found the M&S Dark Chocolate Date Bar contained 26.5g of sugar per serving, for comparison, a standard 51g Mars bar contains around 30g of sugar, so the two aren’t far apart despite one being marketed as a wholesome date-based snack and the other as a chocolate treat. Kellogg’s Rice Krispies Squares Caramel & Chocolate bar came in at 14g of sugar per serving, and the Deliciously Ella Roasted Peanut Protein Ball, a product marketed heavily on its protein and “natural ingredients” credentials, contained 16g of sugar per serving.
Not every bar in the category is high in sugar, though. The study identified the Grenade Dark Chocolate Mint bar as one of the lowest-sugar options tested, at under 1g of sugar per serving, showing that genuinely low-sugar, high-protein bars do exist, they’re just not guaranteed by the “protein bar” label alone. The gap between the highest and lowest bars in the same category, sold in the same supermarket aisles, is the whole point: you cannot tell which is which without reading the label.
Why “protein” and “healthy” labelling doesn’t mean low sugar
There’s a simple regulatory reason this keeps happening. Terms like “high-protein,” “natural,” “no added sugar” and “high-fibre” are nutrition and marketing claims, each governed by its own narrow legal definition, but none of them is a promise about total sugar content. A bar can legitimately carry a “high-protein” claim (a defined threshold of protein per 100g or per calorie) while still being loaded with sugar from dates, honey, chocolate coating or syrup used to bind and sweeten it.
Compounding this, the researchers point out that rapidly growing categories like protein bars often sit outside the UK Government’s reformulation programmes, which set voluntary sugar and calorie reduction targets for categories like biscuits and confectionery. Because protein bars aren’t yet fully captured by those targets, there’s less structural pressure on manufacturers to cut sugar in this specific category, even as it expands. Combine a fast-growing market, marketing built around health halos, and a regulatory gap, and you get exactly what the study found: a product category where the label’s headline claim and its sugar content can point in completely different directions.
None of this means every “healthy” bar is a trap, or that protein bars have no place in a balanced diet. It means the marketing on the front of the pack is not a substitute for checking the panel on the back.
How to check a protein bar’s sugar content in under 10 seconds
The fastest, most reliable check takes three steps and doesn’t require an app or a calculator:
- Ignore the front of the pack. Skip past “high protein,” “natural” and “no added sugar”, none of these describe total sugar content.
- Find the “Carbohydrates, of which sugars” line in the nutrition table on the back or side of the pack.
- Read the per-100g figure, not the per-serving one. Under UK traffic-light rules: 22.5g of sugar or more per 100g is high (red); 5g or less per 100g is low (green); anything between is medium (amber).
If the pack has a colour-coded traffic-light label, even faster: look for red on the sugars section. If a bar doesn’t carry one, many protein bars don’t, the per-100g “of which sugars” figure on the nutrition table is your answer, and it takes about as long to find as reading the ingredients list.
The takeaway
A “healthy” or “high-protein” label on a snack bar tells you something true about that specific claim, but it tells you nothing reliable about sugar. The Action on Salt and Sugar research shows that more than a third of bars marketed this way in UK supermarkets are high in sugar by the UK’s own labelling standard, and some individual products contain close to, or more than, what you’d get from a standard chocolate bar. The fix isn’t to give up on protein bars, plenty of genuinely low-sugar options exist in the same aisle. It’s to spend ten seconds checking the “of which sugars” line per 100g before it goes in your basket, rather than trusting the front of the pack to do that job for you.
This article is for general information and doesn’t replace personalised dietary advice. If you have specific health conditions such as diabetes, speak to a GP or registered dietitian about your sugar intake.
FAQs
Are protein bars generally high in sugar?
Not all of them, but a large proportion are. A 2025 study by Action on Salt and Sugar found 37% of 458 UK snack and protein bars tested were classed high in sugar under UK traffic-light labelling, and 64% would be considered “less healthy” overall despite being marketed as healthy options.
How much sugar is in the average “healthy” snack bar?
The same study found bars averaged around 7g of sugar and 175 kcal per serving, equivalent to roughly a third of a 7-10-year-old child’s maximum recommended daily intake of free sugars in one snack.
Do protein bars really contain as much sugar as a chocolate bar?
Some do. The study found the M&S Dark Chocolate Date Bar contained 26.5g of sugar per serving, close to the roughly 30g of sugar in a standard 51g Mars bar. Not every protein or snack bar is this high, but the gap between the highest and lowest products in the category is large.
What does “high in sugar” mean on a UK nutrition label?
Under the UK’s voluntary traffic-light system, a food is classed high in sugar if it contains more than 22.5g of sugar per 100g, medium between 5g and 22.5g, and low at 5g or under per 100g.
Why don’t “high-protein” or “natural” labels guarantee low sugar?
Because they’re separate, narrowly defined claims. A product can legally carry a “high-protein” claim based purely on its protein content per 100g or per calorie, regardless of how much sugar, from sources like dates, honey or chocolate coating, is also in the bar.
Are protein balls as high in sugar as protein bars?
They can be. The same study found the Deliciously Ella Roasted Peanut Protein Ball contained 16g of sugar per serving, despite being marketed on its natural-ingredients credentials.
How can I check a bar’s sugar content quickly in the supermarket?
Look at the “Carbohydrates, of which sugars” line on the nutrition table and check the figure per 100g, not per serving. Above 22.5g per 100g is high; 5g or under is low. A red traffic-light label on the sugars section is the fastest visual shortcut where one is shown.
Are there low-sugar protein bars available in UK supermarkets?
Yes. The same study identified bars such as the Grenade Dark Chocolate Mint bar at under 1g of sugar per serving, showing that low-sugar, high-protein options exist in the same category, they’re just not guaranteed by marketing claims alone.
Is fibre content a sign that a bar is low in sugar?
No. The study found that among bars carrying a “high fibre” claim, roughly a third were still high in sugar, so a fibre claim on its own doesn’t tell you anything reliable about sugar content.
Are protein bars a good meal replacement?
Occasionally, a protein bar can be a convenient stand-in, but it isn’t nutritionally equivalent to a balanced meal, and relying on one regularly is worth checking against your own dietary needs. Mintel’s UK Consumer Snacking research found around 1 in 10 UK adults now snack specifically to replace a meal, rising to around 1 in 5 among 20-24 year-olds, so it’s an increasingly common habit worth doing with your eyes open.
