Calories, And How To Read A Label

Almost every packaged food sold in the UK carries the same nutrition panel — there are exemptions, mostly for small producers and unprocessed single-ingredient foods — and once you know what the numbers are made of you can work the rest out yourself rather than trusting anybody's app.

Energy is not measured, it is calculated — from the grams of each nutrient, using conversion factors set in law. They are in Annex XIV of the assimilated Food Information to Consumers Regulation (1169/2011), and they are the same on every label in the country: protein 4 kcal per gram, carbohydrate 4, fat 9, fibre 2, polyols 2.4, alcohol 7. That is the whole arithmetic. Fat carries more than twice what protein and carbohydrate do per gram, which is why it moves a total fastest and why the same weight of two foods can differ enormously.

Polyols are worth knowing about if you eat protein bars or anything sold as low sugar: they are sweeteners that carry 2.4 kcal per gram rather than sugar's 4, which is how a bar can be lower in sugar without being much lower in energy.

The percentages beside them are Reference Intakes — a labelling convention, set in Annex XIII of the same Regulation, based on an average adult eating 2,000 kcal (8,400 kJ) a day. It is a yardstick for comparing products in a shop, not a target for you. Someone lifting four times a week and walking to work needs more than that; someone smaller and sedentary needs less. Treat the % column as "how much of a typical day's food is in this packet", which is the question it can actually answer.

The next paragraph has example calorie numbers.

Putting it together with the rest of this guide, at 84kg. Near the BOTTOM of each range — protein 1.6g/kg, carbohydrate 5g/kg, fat 0.8g/kg, which is the middle of the fat range rather than its floor — that is 134g, 420g and 67g, which at 4, 4 and 9 kcal per gram comes to roughly 2,800 kcal. Run the same sums at the TOP of the same ranges and you get about 3,850. Take fat down to its actual floor of 0.6g/kg and the lower figure is nearer 2,670.

That span is the point, and it is why this article does not give you a number. The guide describes someone eating somewhere between 2,800 and 3,850 kcal a day — and the lower figure is the floor, not the target. If you are training four or five times a week and eating well under 2,800, the thing to examine is whether you are eating enough, not whether you are eating precisely.

Two things that arithmetic does not tell you. It is an estimate built on estimates, so treat it as an order of magnitude rather than a budget to hit. And a total says nothing about whether a diet is any good: 2,800 kcal of biscuits and 2,800 kcal of food you cooked are the same number and a completely different week.