What does calorie intake mean: what you eat, or what you need?
Both, and the answer depends on which one you meant. Your intake is what you actually take in over a day: that is recorded, from labels, reference values and estimates, when you log what you eat. Your requirement is what your body uses, which a calculator estimates from your age, sex, height, weight and activity. The first is a fact you can collect; the second is an estimate you can only refine.
The question is usually asked for the second reason: a number to aim for. The usual answer is a calculator, which hands back a figure with more confidence than it has. The order that works is the other way round: record first, for a few weeks, and let the record and the scale say what the formula could only guess.
This page does both, in that order. How a record finds what you eat, how a calculator estimates what you need and how far to trust it, and how the two meet in a target you can live with. IZeat is the record: it computes no formula, and the target it compares each day to is the one you chose.
How do you find what you actually eat in a day?
By writing down every item with its quantity and where its calories came from, adding the day up, and reading the average over the days you recorded. A packaged food has its energy per 100 g on the nutrition label; a plain food has a public value in a food composition table; a plate nobody weighed is an estimate, and an honest record says so.
Two things decide whether the number is worth anything. The first is what changes a figure most: whether a weight was raw or cooked, since dry rice is about 365 kcal per 100 g and cooked about 130 in USDA FoodData Central, read 15 September 2026, and the fat a food was cooked in, about 88 kcal for 10 g of oil in the same table. The second is the days you skip: an average taken over recorded days only is honest; an average that fills a blank day with zero is a false figure about your intake.
The obstacle is not the arithmetic, it is the keeping. In a 2019 trial by Harvey and colleagues, logging took about 23 minutes a day in the first month; in two other trials reported by Turner-McGrievy and colleagues, fewer than half the participants were still recording after ten weeks. A record that costs less to keep is the one that lasts long enough to answer the question.
How do calculators estimate what you need, and how far can you trust them?
They estimate your resting energy from age, sex, height and weight with a published equation, then multiply by an activity factor, a multiplier that rises with how much you move: in the FAO/WHO/UNU scale, read 16 September 2026, from about 1.4 for a sedentary life to 2.4 for a vigorous one. The result is a TDEE, total daily energy expenditure, and it is an estimate at both steps. Trust it as a starting point, not as a measurement.
The equations disagree with each other and with measurement. The best studied, Mifflin-St Jeor, landed within 10 percent of the measured resting figure for most people, not all, in a 2005 systematic review by Frankenfield and colleagues; the older Harris-Benedict equation overestimated by 5 percent in the sample the newer one was built on. The activity factor is the larger uncertainty, because it rests on a self-assessment of how active you are, and one category up the scale adds roughly a fifth to the whole estimate. Two people with the same body can get figures a fifth apart from the same site, depending on which box they ticked.
| The way to find it | What it gives you | Where the uncertainty sits | What it costs you |
|---|---|---|---|
| A calorie calculator | An estimate of what your body uses in a day | The equation chosen, and above all the activity factor you pick | A few minutes and a guess about your activity |
| A food record over a week | What you actually ate, per recorded day | The sources of the figures and the days you did not record | A line per item, or a sentence per meal with IZeat |
| A record beside your scale over several weeks | Whether your intake sat above, below or at what you use | A complete record and patience; water and a full stomach on the scale | Weeks of both |
| A clinician | A target set for you, with your history in view | Their estimate is still an estimate, informed by more than a formula | An appointment |
Bottom line: a calculator estimates what you need; only a record shows what you eat; the two together, over weeks, are the closest thing to a measurement most people will get.
IZeat applies none of these formulas, on purpose: it records what happened and compares it to the target you chose. If you want an estimate, the assistant you already use can reason about one with you, outside IZeat, and say which equation it used; IZeat stores only the target you then choose.
How do you turn an intake into a target you can live with?
By starting from what you actually eat, not from what a formula says you need. A week or two of records gives you your real average; your scale over the same weeks says whether that average held your weight, added to it or drew on it. From there, a target is a decision you make, alone or with someone qualified, and the record shows whether you kept to it.
The public health services describe a pace rather than a personal number: the CDC writes that people who lose weight at a gradual, steady pace of about 1 to 2 pounds a week "are more likely to keep the weight off than people who lose weight quicker", read 14 September 2026, and NHS services put the same pace at around 0.5 to 1 kg a week. That is their figure, not IZeat's; how it applies to you is between you and whoever advises you.
In IZeat the target is set by conversation, from the day you say, and changed the same way: "from Monday, 2 100 kcal" starts a new period, and the days before keep the target that was theirs. IZeat never sets, raises or lowers one on its own. An adult may set what they want; what the record adds is the honest comparison, day after day, written the same way whether the day landed over or under.
How can you read your own intake from the record?
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. It is designed to make the record easier to keep while you work toward your goal, less weight or more muscle, and the record is what answers the intake question.
After a fortnight of meals said to your assistant, you ask what you averaged. The assistant reads the period from IZeat: the average per recorded day, how many of the fourteen days had entries, and the target that was in force. You put that beside your own scale, which IZeat does not record today, and decide: keep the target, or say a new one from Monday. IZeat records the new target from that day, and the next reply compares the day to it. The reasoning about where maintenance sits was the assistant's and yours; the figures were the record's.
- The average is taken over the days you recorded. A day with no entry is shown as a day with no entry, never filled in with a zero or a guess, so the average says what it says.
- The target is yours, from the day you say. Chosen by conversation, changed the same way; IZeat computes no TDEE and recommends no deficit.
- Every meal receipt carries the day so far and what is left. So the question is answered while there is still a meal to decide, not when the day is over.
The limit, plainly: IZeat records intake, one side of the energy balance, and estimates nothing on the other side; it records no weight today and applies no activity factor. What it gives you is a record honest enough to put beside your scale, which is where a calorie intake stops being a guess.
Frequently asked questions
Short answers to the questions people type, each one sourced above.
How many calories should I eat a day?
Nobody can tell you from a page, and this one will not try. What a calculator gives is an estimate of what your body uses, uncertain by a margin that matters for a daily target; what a record gives is what you actually eat; the public health services describe a pace of loss rather than a personal number. A figure for you comes from your own record beside your scale over some weeks, or from a clinician; IZeat records the target you then choose and compares each day to it.
How do I calculate my maintenance calories?
The formula way: estimate your resting energy from age, sex, height and weight with a published equation, then multiply by an activity factor, about 1.4 to 2.4 in the FAO/WHO/UNU scale. Expect a range: the best-studied equation lands within 10 percent of measurement for most people, and the factor is a guess. The observed way: record what you eat for a few weeks while your weight holds; the average per recorded day over that time is an estimate of your maintenance with the record's own uncertainty in it, from your own life rather than a table.
Does IZeat calculate my TDEE?
No, and it never turns one into a target. IZeat's rule is that any formula it used would have to be named and sourced, and it uses none for the body: it records what you ate, with the source on each item, and compares each day to a target you chose. If you want a TDEE estimate, the assistant you already use can reason about one with you, outside IZeat, and IZeat stores only the target you decide on afterwards.
How accurate are calorie intake calculators?
Accurate enough to start from and not enough to live by. The resting figure comes from equations that land within 10 percent of measurement for most people, not all, in a 2005 review; the activity factor multiplies that error, and it rests on your own guess about how active you are. A calculator's result is a range dressed as a number. A few weeks of a complete record beside your own scale can correct it, in whichever direction your body actually goes.
Can ChatGPT calculate my calorie intake?
It can estimate what you might need, from the same equations a calculator uses, and it can say which one it used and how wide the range is; that reasoning is its own, outside IZeat. What it cannot do alone is find what you actually eat, because that takes a record kept across days. Connected to IZeat, the same ChatGPT records each meal you describe, and reads back the average per recorded day when you ask.
What is the difference between calorie intake and maintenance calories?
Intake is what you take in, a fact about your days; maintenance is the intake at which your weight stays the same, a property of your body that moves with activity, weight and time. You measure the first by recording; you find the second by watching what the first does to the scale over weeks, or by estimating it with a formula. A target sits above, below or at maintenance, and is a choice.
How many days do I need to record to know my intake?
More than one, because days vary, and enough for the average to settle; a week shows the shape, a fortnight or a month shows the level. IZeat averages over recorded days only and says how many days that was, so a short or patchy record reads as short or patchy rather than as a precise figure. For maintenance rather than intake, you also need the scale over the same weeks, which IZeat does not record today.
What if the target I set is too low?
IZeat records what an adult sets and does not block or lecture; the target is yours. Over and under are written the same way, and a low day is never congratulated. The pace the public health services describe is gradual, about 1 to 2 pounds a week, and a target well below what your record and your scale suggest you use is a conversation to have with someone qualified, not with a tracker.