How to Read UK Food Labels: Traffic Lights, Portions and Protein
To read a UK food label quickly, start with the per 100g column to compare products fairly, then check the portion size the front label is based on, then look at the traffic lights for fat, saturates, sugars and salt. If you are training, add one more check: grams of protein against calories. Red does not mean “never” and green does not mean “unlimited”. The labels tell you how a product compares, not whether it fits your day. Once you know the order, it takes about thirty seconds per product.
Here is what each part means and how to use it in an actual supermarket, not in theory.
The two places nutrition information appears
Most packaged food in the UK has two labels.
- Front of pack: the colour-coded panel showing energy, fat, saturates, sugars and salt, usually per portion, with traffic light colours and a percentage of your reference intake. This is voluntary, but most major supermarkets use it.
- Back of pack: the nutrition table, which is required on most pre-packed food. It always shows values per 100g (or 100ml) and often per portion too. Protein, carbohydrate and fibre live here, not on the front.
The front is for a quick glance. The back is where the useful detail is.
What the traffic lights mean
The colours are based on fixed thresholds per 100g, set out in UK government front-of-pack guidance. For foods (drinks have lower thresholds), they work like this:
| Per 100g | Green (low) | Red (high) |
|---|---|---|
| Fat | 3g or less | More than 17.5g |
| Saturates | 1.5g or less | More than 5g |
| Sugars | 5g or less | More than 22.5g |
| Salt | 0.3g or less | More than 1.5g |
Anything in between is amber. The NHS guide to food labels sets out the same figures if you want the official version.
Where the lights mislead
Traffic lights rate nutrients in isolation. Olive oil is red for fat. Nuts are red for fat. A tub of plain Greek yoghurt may show amber for saturates. All of these can sit very comfortably in a sensible diet. Meanwhile, a low-fat sweetened yoghurt might look greener and be less filling. Use the colours to compare similar products, not to judge whole foods.
Sugars include natural sugars
The “sugars” figure includes sugar naturally present in milk and fruit, not just added sugar. Plain yoghurt shows sugars from lactose. A fruit-based snack bar may look high mostly because of dried fruit. To see if sugar has been added, check the ingredients list for sugar, syrups, honey, fruit juice concentrate and similar.
Per 100g versus per portion
This is where most people get caught out. The front of pack usually shows values per portion, and the manufacturer chooses the portion. A bag of granola might base its label on 45g, which is a smaller bowl than many people pour. A pizza might be labelled per half.
Two habits fix this:
- Compare products using per 100g. It is the only column that is like for like.
- Check the portion against what you actually eat. If you pour twice the stated portion, double the front-of-pack numbers in your head.
Reference intakes, briefly
The percentages on the front are based on reference intakes for an average adult. The figures used on UK labels are: energy 8,400kJ / 2,000kcal, fat 70g, saturates 20g, carbohydrate 260g, total sugars 90g, protein 50g and salt 6g. They are not personal targets. A tall man who trains four times a week, and a smaller, less active woman, need different amounts. Treat the percentage as a rough sense of scale, nothing more.
Reading labels for training: the protein check
If you are lifting and trying to lose fat or build muscle, protein is the number most worth checking, and it is only on the back. A quick way to judge it: look at protein per 100 calories.
- Around 10g of protein or more per 100kcal: protein-rich. Many plain yoghurts, cottage cheese, lean meat and fish sit here.
- Around 5g per 100kcal: moderate. Many cereals, breads and mixed dishes.
- Under 3g per 100kcal: low. Most biscuits, crisps and sweets.
This is a rule of thumb rather than an official standard, but it quickly separates genuine high-protein foods from products with “protein” on the wrapper. A “protein” cookie can still have more energy from sugar and fat than from protein. Our list of high-protein snacks you can buy in any UK supermarket applies this check in practice, and how much protein you need to lose fat covers daily targets. When I work with clients in private personal training sessions, this one habit usually does more for their eating than any meal plan.
A thirty-second label routine
- Turn the pack over.
- Look at energy per 100g, and the portion size you will actually eat.
- Check protein: is it worth its calories for your goal?
- Check fibre if it is bread, cereal or a snack bar; more is generally better.
- Glance at saturates and salt, particularly for processed meats, ready meals and sauces.
- Scan the first three ingredients. Ingredients are listed by weight, so the first few make up most of the product.
Claims on the front of the pack
“Light”, “lighter” or “reduced” means lower than a standard version of the same product, not necessarily low. A reduced-fat crisp is still a crisp. “High protein” has a legal meaning, but it is about the share of energy from protein, not about the product being a good choice. “Natural” and “wholesome” have no useful nutritional meaning. Read the table, not the slogans.
If you are interested in the bigger picture on packaged food, our post on ultra-processed food and training takes a practical, unfussy view.
A note for specific health needs
If you are managing diabetes, high blood pressure, kidney disease, coeliac disease or a food allergy, labels matter in more specific ways. Check with your GP or a registered dietitian for advice tailored to you. Allergens are always emphasised in the ingredients list, usually in bold.
Questions we get asked
Should I avoid all red traffic lights?
No. Use them to compare similar products and to notice what you eat often. Plenty of nutritious foods show red for fat.
Why do the front and back numbers differ?
The front is usually per portion and the back gives per 100g as well. They describe the same product in different units.
Are calories on labels accurate?
They are close enough to be useful for planning. Small differences between the label and the actual product do not matter much over a week.
Can you help me with nutrition alongside training?
Yes, I give practical guidance as part of coaching, and refer to a GP or dietitian where it is needed. How sessions work, and prices, are on the Highgate personal trainer page.
Book with The Highgate House
Ready to start training properly? Email us at [email protected] with the service and the day that suits you, and we will come back to you with times.
Visit The Highgate House · Private personal training
The Highgate House, Archway Road, Highgate, London N6.
