What does a nutrition label actually tell you?
The producer's declared values for that product: energy and nutrients per 100 g or 100 ml, and in some regions per serving. In the European Union the energy is computed from the declared grams with fixed factors, 4 kcal per gram of carbohydrate and protein, 9 per gram of fat, 7 per gram of alcohol, 2 per gram of fibre, under Regulation (EU) No 1169/2011, Annex XIV, read 14 September 2026.
That makes a label a source you can check against the pack, and a declaration all the same: it describes the product, not the portion on your plate, and it describes it as the producer computed it. Reading it is where the record is won or lost. A label read right is a figure you can lean on; a label read wrong is a guess with a certificate.
Labels differ by country in unit and in basis: the same yoghurt can read in kilojoules or kilocalories, per 100 g or per serving with a serving weight, depending on the shop it came from. The assistant's first job is to say which way it is reading, and yours is to check it against the pack. That readback is the one habit that catches a misread before it becomes a row, and it is the practical half of how far to trust a model's figure.
How does the assistant read a label, and what does it add?
It reads the values and says them back before anything is recorded, with the unit and the basis: per 100 g or per serving, kJ or kcal. Then it asks how much you ate and scales the figures to it. That readback is the moment you can catch a misread, a comma taken for a point, 1.2 g read as 12; it is a check you make, not a guarantee that every error is seen.
It can add what it sees. When a kilojoule figure sits where a kilocalorie was meant, or when the energy does not fit the declared grams, it can say so and propose an interpretation, and then it is a question for you to settle with the pack in hand, not a verdict on the manufacturer. Laetitia, who builds IZeat with Seb, sent a fig-jam label in September 2026: the assistant first read the energy as about 57 kcal per 100 g, then pointed out that 60 g of carbohydrate per 100 g did not fit the 240 kJ it had read, proposed 240 kcal per 100 g instead, and asked how much she would use. She said 15 g, and the breakfast was updated. An interpretation and a check, with a first reading it then revised; the transcript alone does not prove the label was wrong, nor that the second reading was right, and a figure accepted on the assistant's reasoning rather than found on the pack is an interpretation, which the record should carry as an estimate quoting the label rather than as the declaration itself.
The division of labour is the point. IZeat's protocol says what must be read back and asked before an item is stored, and IZeat keeps the result with the label as its source. The reading, the unit explanation and the coherence check are the assistant's reasoning, following that protocol; a proposed corrected value is a proposal, recorded only when you accept it.
What goes wrong when a label is read, and how do you check it?
Two mistakes carry most of the damage. A kilojoule figure taken for kilocalories, since one kilocalorie is 4.184 kilojoules, records a food about four times too heavy. A per-serving figure applied to a bigger portion, or taken for a per-100 g figure, records it wrong by whatever the serving was. Both are easier to catch when the basis is said out loud: 380 kJ per 100 g, 125 g eaten, about 114 kcal.
| What the label says | The misread | What a readback sounds like | What is recorded |
|---|---|---|---|
| 380 kJ per 100 g | 380 kcal per 100 g, four times too high | "380 kJ per 100 g, about 91 kcal; for 125 g, about 114 kcal" | The item with the label as source, in kcal, your grams beside it |
| Per serving of 30 g: 150 kcal | 150 kcal for the 60 g you ate | "150 kcal per 30 g serving; you ate 60 g, about 300 kcal" | The item scaled to 60 g, label as source |
| Fat 1,2 g per 100 g | 12 g of fat | "1.2 g of fat per 100 g" | 1.2 g, scaled, label as source |
| Carbohydrate 60 g, energy 240 kJ | Recorded as printed | "60 g of carbohydrate would give about 240 kcal, not 240 kJ; which is it?" | Nothing until you settle it; then what you confirm |
Bottom line: say the unit and the basis out loud and the two commonest misreads show themselves before they are recorded.
The energy-to-macros check is the last line of the table, and it is a cue, not proof. Multiply the grams of protein and carbohydrate by 4 and the grams of fat by 9; the sum lands near the printed energy. A small gap is fibre, counted at 2 kcal per gram, alcohol, polyols or rounding; a large one, or kJ and kcal columns that disagree, is a reason to look again at the pack, not a finding that the label is wrong.
What does a barcode get you, and what does it not?
A product record: someone's transcription of that product's label, at the time it was entered. It saves the typing and it is usually right. What it does not establish is that the record matches the pack in your hand: recipes change, sizes change, a regional version differs, and a crowd-sourced record can have been typed from a different pack or typed wrong.
So retrieval and verification are two steps, and the second is the one that matters for the record. The pack in front of you is the evidence; the record is a shortcut to it. When the two disagree, the pack wins, and the assistant can compare them for you if you give it the record you found and a photo of the pack.
IZeat has no scanner and no database of its own, today. What is read is the label you photograph or say; the assistant may recognise a product from its own knowledge, and that recognition is a record to compare, not a reading of your pack. The source stored is the label when the label was read; anything the assistant reasoned rather than read is an estimate, and says so.
How can you log a packaged food from its label without typing it?
IZeat is the calorie tracker inside ChatGPT, Claude or any other assistant. Tell the assistant you already use what you ate instead of searching for foods and entering them one by one. For packaged food that means the label is a photo, read back to you before it is stored, which is designed to make the record easier to keep while you work toward your goal.
Breakfast: you photograph the yoghurt's label and say "I had 125 g". The assistant reads it back: 380 kJ per 100 g, about 91 kcal, 5 g of protein, 10 g of carbohydrate, 3.5 g of fat; for 125 g, about 114 kcal, converted from kJ. You confirm, or correct a figure, and IZeat records the item with the label as its source, your 125 g and your words beside it, and returns the receipt with the day so far. If the assistant had seen an energy figure that did not fit the grams, it would have said so and asked you to look at the pack before recording anything.
- You log a packaged food by showing it, not by typing it. The label is read for you and repeated with its units; you say the portion, the assistant scales the declared values to it, and IZeat records the result with your grams beside it.
- You can catch a misread before it becomes a meal. The readback is where 1.2 g taken for 12 g, or kJ taken for kcal, is seen, by you or by the assistant; a correction is a sentence, and the item is corrected before anything else is done.
- You know which figures were declared and which were estimated. A label item carries the label as its source, beside the plate that was estimated and the food you weighed, so the day says how much of it was read from a pack.
The limit, plainly: a label declares the product, not the portion you ate, and a readback helps you spot an error without detecting every one. IZeat stores what the label says, in kilocalories, and names the label as source; if a declared value is wrong on the pack, the record is wrong with it, and says where the figure came from so you can find out.
Frequently asked questions
Short answers to the questions people type, each one sourced above.
How do you convert kilojoules to calories?
Divide by 4.184: one kilocalorie is 4.184 kilojoules, by definition rather than by estimate, so 380 kJ per 100 g is about 91 kcal. European labels print both, so the kcal column is the one to read; where a label prints kilojoules only, the assistant can convert and say which column it read. IZeat records in kilocalories with the label as source, and the reply repeats the converted figure so the conversion is checked in the same breath.
Is a nutrition label accurate?
It is the producer's declared value for that product, computed from the macronutrient grams with fixed factors in the European Union, and it is a source you can check against the pack. It is not a measurement of your portion, and a declaration can be wrong on the pack. What goes wrong more often is the reading: kJ for kcal, per serving for per 100 g. The assistant reads the values back before anything is recorded, which is where those are caught, though no check catches every error.
What is the difference between per 100 g and per serving?
Per 100 g is a rate, the same for any amount; per serving is a figure for an amount the producer chose, printed with its weight, and often smaller than what a person eats. American panels lead with the serving; European panels with 100 g. The assistant says which basis it read and scales it to the grams you ate; if you say "one serving" or "half the pack", those words are kept next to the grams so you can check later.
Does IZeat scan barcodes?
No, and it has no product database, today. A barcode retrieves someone's record of a product; it does not show that the record matches the pack in your hand, whose recipe or size may have changed. IZeat's path is the label itself: photograph it or say the values, the assistant reads them back with their units, you confirm the portion, and the item is recorded with the label as source. A record the assistant recognises is something to compare with the pack, not a reading of it.
Does a label give calories per 100 g or per pack?
Per 100 g or 100 ml on most European labels, sometimes per serving beside it, and rarely per pack. The pack total is the per-100 g figure times the pack weight, which is printed elsewhere on the packaging. Say "the whole pack" or "half the pack" and the assistant can work it out from the weight and say the figure back; IZeat keeps your words next to the grams it recorded, so a pack eaten in two sittings reads as two halves.
Can ChatGPT read a nutrition label?
Yes, from a photo or pasted text, and it is the input that can be checked against the pack. Through IZeat it is asked to read the values back with their units and basis before recording, to say when an energy figure does not fit the grams, and to ask how much you ate; the item is then recorded with the label as source, scaled to your portion. The reading and any flagged mismatch are ChatGPT's; the record and its source are IZeat's.
What if the label's energy does not match its macros?
Look at the pack again before recording. The assistant can say when 4 times the carbohydrate and protein plus 9 times the fat lands far from the printed energy, or when a kJ figure seems to sit under a kcal heading, and propose an interpretation, as it did for a fig jam in September 2026. Fibre, alcohol, polyols and rounding explain a gap before a misprint does. What you confirm from the pack is recorded with the label as source; a value deduced and accepted without finding it on the pack is an estimate that quotes the label.
Why is a label photo better than a plate photo?
Because the label is a declared value and the plate is a guess. A photographed label is read, repeated with its units, checked against the grams and scaled to what you ate, then recorded with the label as source. A plate photo names the dish and cannot show how much is on it or what it was cooked in, so IZeat's protocol has the assistant ask for a portion cue and the cooking fat before any number, and record an estimate that says so.