The Small Print Diet: What UK Food Labels Aren't Telling You About Calories

You've done everything right. Scanned the barcode, checked the calories, weighed it against your daily target. Except the number on the front of the pack might be off — legally off — by enough to quietly stall your progress.

UK food labelling isn't a lie, exactly. It's more like a magic trick: entirely honest, and expertly misdirected. Here's what's actually going on behind that traffic light wheel, and how to out-read it.

The Rounding Rules That Add Up

Under retained EU law (which the UK still effectively follows for labelling), energy values don't need to be precise. They're declared in rounded increments — and for low values, the rounding gets generous.

A product with, say, 4 calories per serving can be labelled as '0'. A spray oil claiming '1 calorie per spray' might genuinely contain more, but the rules let it round down. Use ten sprays across your cooking and you've banked a small, invisible surplus. Multiply that across a few 'guilt-free' products a day and you've got a gap between the label and the reality that no amount of meal planning can account for.

The same logic applies at the other end. A ready meal listed as 394 kcal could legally be meaningfully higher once declared values are rounded and testing tolerances are applied. No single product is wildly out — but across a weekly shop, the drift compounds.

Per Slice, Per Biscuit, Per 'Portion'

The sneakiest trick isn't the numbers — it's the serving size. That £1 pack of biscuits is 'only 85 calories per biscuit', printed proudly on the front. The pack contains eight. Nobody eats one.

Ready meals love a 'per half pack' declaration, because half a lasagne looks like a sensible dinner. Always check what the 'portion' actually is before comparing products — a 450kcal meal that's technically two servings is a 900kcal meal, full stop.

Your defence: compare everything per 100g. It's on the back of every pack, it's the law, and it flattens the playing field instantly. Two ready meals might both read 'under 500 calories' on the front — but per 100g, one is 110kcal and the other is 210. Same shelf, very different story.

Traffic Lights: Helpful, But Not Holy

The colour-coded front-of-pack system is genuinely useful for a five-second decision. Red fat? Put it down. But it has blind spots:

• It's based on portion size as declared by the manufacturer — and portions, as we've established, are negotiable.
• It ignores quality. A natural yoghurt with fruit can score worse than a heavily processed alternative with clever formulation.
• It says nothing about ingredients. Sugar can be six different ingredients with six different names, each sitting lower on the list.

Read the ingredients list the way it's written: in order of weight. If sugar, glucose syrup or dextrose appear in the first three ingredients, the traffic light is doing you a disservice.

The Reference Intake Maths Worth Knowing

That 'RI' percentage on the back is based on an average adult diet of 2,000 kcal (women) and 2,500 kcal (men). Useful ballpark, but:

• If you're training hard, your actual needs are likely higher — a '42% of your RI' curry might be a perfectly reasonable post-workout meal.
• If you're smaller, older or less active, that same '30% of RI' sandwich could be half your daily budget.

RIs are averages for average people. You're not average — you're on a plan. Use them as signposts, not commandments.

Your Supermarket Survival Kit

Three habits will cover 90% of it:

1. Per 100g, always. Compare like with like, not portion with portion.
2. Read the serving size first. Before the calories, before the colours — ask 'is this what I'd actually eat?'
3. Favour short ingredient lists. Whole foods — meat, fish, eggs, spuds, frozen veg — don't need labels, which is the biggest loophole of all.

None of this means the label police are out to get you. Most manufacturers are playing by rules that simply permit optimism. But when you're working hard in the gym and the scales won't shift, the answer is often hiding in the small print — not in your discipline.

Read like a lawyer, eat like a knight.