Do you have to count calories? How accurate do you need to be?

Do you have to count calories?

Not forever. If you want to lose fat or build muscle, you need an idea of how much you eat. At the start, accuracy helps because it shows you where you really stand. Over time you need it less and less.

Counting is less accurate than the decimals in the app suggest. In my workbooks the rule is therefore: roughly right and repeatable beats exact and one-off. A method you keep up for months, and that is off by a similar amount every day, gives you more than one perfect week after which you quit. How big the error is for you shows up on the scale over several weeks anyway.

How inaccurate is calorie counting really?

Errors arise in several places at once: in what you record, in what the package says and in what you estimate. Four studies show the order of magnitude:

The Lichtman study is an extreme case. Only ten people had their intake and expenditure measured over 14 days. Their energy expenditure was within 5% of the expected value, so a slow metabolism was ruled out as the explanation. Their actual intake was well above what they reported, and they overstated their activity by 51% on average (Lichtman et al., 1992). The 47% cannot be transferred to healthy people in everyday life. But the review by Livingstone and Black shows that underreported intake occurs in many groups (Livingstone and Black, 2003).

Labels are closer to the truth on average, but not always for an individual product. With the 24 snacks, the extra calories came mostly from larger portions and more carbohydrate than stated (Jumpertz et al., 2013). The selection was a convenience sample, so the numbers do not apply to all products. In the restaurant study, the 13 dishes with the biggest excess that were measured again had 258 to 289 kcal per portion more than stated on average, and dishes with a low stated calorie count tended to contain more than stated (Urban et al., 2011). Both studies tested products from the US; Austria and Germany have their own rules.

Then there is the other side of the equation: your expenditure is an estimate too. Metabolism, daily life, sleep, stress and training status shift the real values, and an activity factor is only a starting estimate.

What a 10 to 15% error means for your deficit

An example calculation. The 10 to 15% error on daily intake is an example value, not a measurement from a study. It sits within the range the studies above show: individual items deviate more, others cancel out. You weigh 80 kg and your total expenditure is 2,500 kcal. A 20% deficit gives a target of 2,000 kcal. In reality you eat a little more than your app shows:

The weekly rate comes from the rule of thumb of 7,700 kcal per kilo of body weight: 500 kcal times 7 days divided by 7,700 is 0.45 kg. An error of only 10 to 15% in intake leaves just 40 to 60% of the planned deficit. The error is small and so is the deficit, which is why it has such a large effect. A rate within the target range of 0.5 to 1% per week drops below it.

The error can also run the other way, and part of it evens out over the week. So a single gram does not matter. A lasting error shows up in the trend, and that is exactly what the weekly trend is for, which I describe below.

When weighing your food makes sense

Weighing is a good tool for calibrating. You use it for a limited time at the start, until you have a feel for how much a portion really is. It pays off most with foods you eat often and that the eye judges poorly, for example rice, pasta, oats, nuts or oil. After a while you know what your portion of rice looks like on the plate and no longer need to reach for the scale every time.

A second time to weigh again is when your trend does not match the plan. First check whether you really eat the calories you think you do and measure them correctly. Only after that do you adjust the target.

The evidence on logging is consistent but weak. A review analysed 22 studies on self-monitoring, and every study on food logging found a link with weight loss. The authors still consider the evidence weak because of methodological limits (Burke et al., 2011). In a 24-week online programme with 142 adults, daily time spent logging fell from 23.2 to 14.6 minutes. People who lost weight logged more often per day, while time per day made no difference (Harvey et al., 2019). That is an association and not proof that logging alone was the cause. It does argue for logging regularly and roughly rather than rarely and very precisely.

Alternatives: portions instead of grams

Once you know the amounts, you can get by without a scale. There are three ways:

• Plate. A meal has four building blocks: vegetables as the bulk, always generous; protein as the anchor, roughly the same at every meal; carbohydrates as the dial, depending on hunger and training day; fat as the fine-tuning in a small amount. The plate method does not replace precise tracking while you are learning. Once you have a feel for the target amounts, it is enough even when you are out and about.
• Fixed meals. If you repeat a few standard meals, you calculate them once and do not have to count afterwards. With meal prep you portion while cooking, so the amount is already in the container.
• Protein first. At every main meal you set the protein source first, spread the daily amount over three to four portions and hit it on rest days as well. At 80 kg and 2.0 g per kilo that is 160 g a day, or about 40 g per meal across four portions. How you arrive at this number is covered in the article How much protein do you really need?.

Rough but repeatable: whether that is accurate enough for you shows in your trend.

How the weekly trend corrects your tracking

The scale is the check on everything that goes wrong when counting. You do not need to know where the error is, whether in the label, the portion or your expenditure. The weekly average shows whether the total adds up. In the first one to two weeks your weight swings widely because of water, so you judge the weekly average over two to three weeks. Why the scale can even go up in a deficit is explained in the article Weight goes up despite a calorie deficit.

The calorie calculator has a collapsible section for this called “Check your real trend”. You enter your latest morning weights, at least 14, one per line, oldest first. You see the weekly average and whether it fits your goal. The values stay in your browser. After three to four weeks you compare the trend with the plan:

Always change only one variable at a time so you can see what worked. In the example above, the average would show only about 0.2 to 0.3 kg per week instead of 0.45 kg. So you see that something is off without having tracked down the error. How to measure your progress beyond the scale is covered in the article Tracking progress, and how the deficit itself works in the article Calorie deficit.

When to leave it

Counting is a means for a phase. In maintenance, a rough weekly structure with flexible details is enough instead of weighing every meal, and weekly trends on the scale are perfectly sufficient. The four building blocks only become a habit once you stop counting them. Then a glance at the plate is enough for most meals.

Single occasions need no counting either. You plan the restaurant visit consciously instead of saving up or overdoing it. Before a party you eat normally, at the party you enjoy it without counting, and afterwards you carry on as usual. A single meal decides little; the overall structure decides a lot.

Also drop counting when it costs more mood than it gives information. After a diet or a build phase, the psychological pattern often weighs more than the calorie question: the fear of losing the result by eating normally, and the urge for even more control.

When to check with a doctor

Counting and weighing can reinforce compulsions in some people. If you have had an eating disorder, if numbers around food trigger anxiety or guilt, or if you only steer your eating by numbers, talk to your doctor before you keep counting. The same applies if you are pregnant or breastfeeding, take medication for diabetes or high blood pressure, or have a kidney or metabolic condition and want to change your eating. This article does not replace medical advice.