Food diary underreporting and why calorie totals can mislead

Recording can change the eating you want to measure

A food record can fall below measured expenditure for more than one reason. Some intake may be omitted or underestimated. The person may also genuinely eat less while recording. A 1990 review compared reported intake with doubly labeled water expenditure in 9 studies. It attributed much of the discrepancy to underreporting, but some participants lost weight during the recording period, indicating that reduced eating also explained part of the gap.[16]

The reports in that review came from recalls or weighed records covering at least 7 days. Expenditure was also measured with doubly labeled water for 7 days or more. Individual differences between reported intake and expenditure ranged from +25% to −76%. Group-average differences were smaller: among non-obese, non-athletic groups in industrialized countries, they ranged from 0% to −20%; in groups with obesity, the averages were −35% and −50%.[16] These are findings from a 1990 review of differing populations, rather than a correction table for today’s diary.

The contrast between individual and group results is important. A relatively small mean discrepancy does not establish that each person’s report was close to expenditure. An average describes the group comparison, while the wide individual range describes a different part of the evidence.[16] Nor does that range tell you where your own report belongs. It shows why the group mean cannot supply an exact answer about an individual meal or day.

Think of someone skipping a snack because entering it feels tedious, or avoiding a mixed dish because its portions are hard to describe. These are everyday examples of how the meal itself might change during recording. If the goal was to observe ordinary eating, the resulting record may instead describe eating organized around the diary. The menu is now serving the diary rather than the other way around. The research distinction is between an inaccurate report and a real change in intake during observation.[16]

Whether this is a problem depends on the question. If you want to know what was eaten on the recorded day, an intentional change is still part of that day’s actual diet. If you want to know habitual intake, days altered for the convenience of recording may not adequately represent it.[16] A change in behavior and the accuracy of its documentation are separate matters. Neither can be inferred solely from the presence of a completed diary.

Suppose the recorded days contain less food, while the unrecorded days are unknown. Filling those gaps with a convenient estimate does not establish usual intake. It is more informative to preserve what remains uncertain and note when the recording process affected meal choices. The 2020 review described person-specific biases in self-reported energy intake and their capacity to weaken apparent relationships between diet and health.[15] The problem reaches beyond whether a daily total seems plausible.

This is also why the research does not support blaming every discrepancy on forgotten food. Omission is one possible explanation, while actual intake reduction during recording is another.[16] The two can lead to different interpretations of the same intake–expenditure comparison. Before using a diary to answer a question about usual diet, consider whether the diary describes your normal meals or a temporary routine shaped by being observed.

Large datasets and difficult conversations have limits too

Adding more reports does not automatically solve biased measurement. A 2025 study used 6,497 doubly labeled water measurements in people aged 4–96 to develop an equation predicting total energy expenditure from readily available variables such as body weight, age, and sex. When the equation was applied to large dietary survey datasets, the level of misreporting exceeded 50%.[3] This was a method for identifying unreliable dietary data, rather than a trial of a weight-loss strategy.

As misreporting increased, the reported macronutrient composition also showed systematic bias. The researchers found that this could produce apparently meaningful but potentially spurious associations between dietary components and BMI.[3] This is a measurement warning. It does not establish that a particular nutrient caused the observed differences in body size. The way diet is reported can influence the relationship an analysis appears to find.

An expenditure prediction is different from measuring expenditure directly in every survey participant. The study used 95% prediction limits to support screening for misreporting.[3] Those limits are part of the assessment, rather than incidental information. Screening uses a defined comparison with a range of predicted values.

The distinction also helps separate this topic from basal metabolic rate calculators. The equation here predicts total energy expenditure; the related feature on basal metabolic rate estimation addresses a different measurement question. A calculation displayed as a precise number still needs to be interpreted according to what it predicts and how its uncertainty is handled. This study’s contribution concerns the limits of dietary measurement and the associations derived from it.[3]

Social discomfort does not supply a simple explanation either. A small exploratory pilot study in 2024 involved 39 weight-stable adults with overweight or obesity. They completed 3 separate 24-hour recalls, a resting metabolic rate measurement, psychological questionnaires, and interviews. Weight stigma was reported by 64.1% of the sample, but the stigma-related measures did not predict the accuracy of reported energy intake.[19] The finding does not support assuming that a person’s experience of stigma tells you how accurately they report food.

Participants described wanting to report accurately even while worrying about foods they regarded as socially undesirable.[19] An uncomfortable reporting conversation and a lack of intention to be accurate are different things. This study was not a doubly labeled water validation, and the authors called for work in larger, more diverse groups with objective measurements such as doubly labeled water.[19] Its size and measurement approach limit the conclusions, including any claim that stigma has no role in every setting.

Common misconceptions

“Underreporting means people are hiding overeating.” This reads intent into a result that does not measure intent. The adult systematic review found underreporting across several assessment methods, with differing degrees of error within the same method.[5] In the 1990 review, individual intake–expenditure discrepancies extended from +25% to −76%, including reports above as well as below expenditure.[16] A discrepancy defines a comparison problem. It does not, by itself, explain why the participant’s answer differs.

“A diary that calculates automatically must be accurate.” The 16 studies involving technology-based methods were among the majority that reported significant underreporting compared with doubly labeled water.[5] Automating arithmetic and validating the food and portion entered are separate tasks. A detailed number appearing after you select a dish does not show that the selection or amount matched what you ate. The interface can display precision without independently verifying intake.

“If the average error is known, I can add that percentage to my own diary.” The 15–17% and 18–21% averages came from particular assessment methods in adults aged 50–74.[9] They are group findings under specified conditions, not individualized adjustments. Applying the same percentage to every day assumes the person’s errors match that average. These data do not establish that assumption or identify the correct calorie content of tonight’s meal.

None of this requires throwing away a diary. The studies discussed here mainly examine its validity as a tool for measuring intake.[5][9] Using a record to reflect on habits, or testing whether the act of recording supports weight loss, asks different questions. The feature on food tracking and weight loss addresses those issues; a finding about measurement accuracy cannot substitute for evidence about behavior change or weight outcomes.

A record can still preserve an event whose quantity is uncertain. “I ate something after lunch” contains information even if the portion cannot be reconstructed. Conversely, naming a dish does not establish its exact amount. Keeping those distinctions visible lets you choose questions the record can answer. It also keeps uncertainty from being silently replaced with a familiar number simply because the entry form expects one.

What you can do today

• Keep your usual menu during the 4-day recording period used in the 2018 validation study. Choose meals as you normally would rather than changing the menu to make entries easier; the aim is to observe your usual eating.[9]
• Avoid skipping a usual snack or choosing a different dish solely because recording it is inconvenient. The review covering at least 7 days of intake reports and 7 days or more of expenditure measurements found that actual reductions in eating explained part of the discrepancy.[16]
• Keep the 4-day record together, marking estimated portions as estimates. Include remembered tastes and drinks even if their quantities are uncertain, explain blanks, and note any meal changes caused by recording. Compare those meals with your usual eating instead of adding the study’s average error percentage to your total.[9][16]
• The next morning, reconstruct the previous 24 hours of food and drinks, moving through meals and the times around them. Repeated recalls still underestimated energy by 15–17% on average in the validation study, so a completed entry does not establish an accurate quantity.[9]

Give movement its own calendar at On the Shore Tachikawa

Keep the task of estimating food intake separate from the habit of making time to move. On the Shore Tachikawa provides a place to continue the latter, with visits entered in your calendar separately from your food diary.

Yoga choices span 25+ kinds of lessons, including both lava-stone hot yoga and room-temperature yoga. The studio also offers personal training, Pilates, HIIT, boxercise, and women-only kickboxercise. Many of our yoga instructors speak English, and the studio’s owner often helps guests from the US bases in English herself.

For a 60-minute yoga trial, the tax-inclusive price is ¥1,980; mat rental, 2 bath towels, and 1 face towel are included. Before using the yoga trial booking link, check the participation conditions against your circumstances and the lesson against your schedule.

Anyone instructed by a doctor to stop exercising cannot join. Pregnant guests cannot take lava-stone hot yoga lessons; room-temperature maternity yoga is available for pregnancy.

Find the studio at 3F Etoile Bldg, 2-14-10 Akebonocho, Tachikawa, Tokyo, a 1-minute walk from JR Tachikawa Station’s North Exit. It is open every day 8:00–23:30. Visit the studio’s website for details and its pricing page for prices.

References

1. Representation of adults with class III obesity in studies assessing validity of self‐reported energy intake using doubly labeled water: A systematic review — Erica M. Howes et al., 2024, Obesity Reviews. DOI: 10.1111/obr.13713
2. Dietary misreporting: a comparative study of recalls vs energy expenditure and energy intake by doubly-labeled water in older adults with overweight or obesity — L. S. Santos-Báez et al., 2025, BMC Medical Research Methodology. DOI: 10.1186/s12874-025-02568-4
3. Predictive equation derived from 6,497 doubly labelled water measurements enables the detection of erroneous self-reported energy intake — Rania Bajunaid et al., 2025, Nature Food. DOI: 10.1038/s43016-024-01089-5
4. Validity of Dietary Assessment Methods When Compared to the Method of Doubly Labeled Water: A Systematic Review in Adults — T. Burrows et al., 2019, Frontiers in Endocrinology. DOI: 10.3389/fendo.2019.00850
5. Obese individuals do not underreport dietary intake to a greater extent than nonobese individuals when data are allometrically‐scaled — S. Waterworth et al., 2022, American Journal of Human Biology. DOI: 10.1002/ajhb.23743
6. Comparison of self-reported dietary intakes from the Automated Self-Administered 24-h recall, 4-d food records, and food-frequency questionnaires against recovery biomarkers. — Yikyung Park et al., 2018, The American journal of clinical nutrition. DOI: 10.1093/ajcn/nqx002
7. Traditional Self-Reported Dietary Instruments Are Prone to Inaccuracies and New Approaches Are Needed — M. N. Ravelli et al., 2020, Frontiers in Nutrition. DOI: 10.3389/fnut.2020.00090
8. Inaccuracies in self-reported intake identified by comparison with the doubly labelled water method. — D. Schoeller et al., 1990, Canadian journal of physiology and pharmacology. DOI: 10.1139/y90-143
9. The Impact of Weight Bias and Stigma on the 24 h Dietary Recall Process in Adults with Overweight and Obesity: A Pilot Study — Erica M. Howes et al., 2024, Nutrients. DOI: 10.3390/nu16020191
10. Markers of the validity of reported energy intake. — M. B. Livingstone et al., 2003, The Journal of nutrition. DOI: 10.1093/jn/133.3.895s

Cover photo: Sugar is weighed in a home kitchen while preparing ingredients for a cake. (Photo: Wald1siedel / CC BY-SA 3.0 / Wikimedia Commons)

Information as of October 2026. For your own health, consult a doctor.

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