Guide
When a clinician asked you to.
Someone at a clinic asked you to write down what you eat. That is a different job from tracking calories for weight. It has a start date, an end date, and a reader. This page reports what clinicians ask for, and it is not medical advice. It covers what to record, how many days, what each condition needs, and how to hand it over.
Not on this page. How exact your everyday calorie logging needs to be, and what to do on the days you go over, is handled on /how-close-to-your-calorie-target/.
What does a clinician mean when they ask you to keep a food record?
A food record is a short, dated account of everything you eat and drink, with amounts, over a window the clinic picks. The renal service at Hull University Teaching Hospitals asks for 3 days: 2 weekdays and 1 weekend day. It samples your usual diet, then stops.
This page reports what clinical services ask patients to record. It is not medical advice. The plan to follow is the one your own clinician set with you. An AI photo estimate is never an appropriate input to an insulin dose.
The Hull University Teaching Hospitals NHS Trust renal food diary names the days: 2 weekdays between Monday and Friday, 1 of them a dialysis day for people on hemodialysis, plus Saturday or Sunday. Everything eaten and drunk goes down with its amount.
Three days is not universal. The Monash-authored FODMAP implementation guide describes a 7-day diary before the consultation. Short windows are deliberate: the National Cancer Institute dietary assessment primer says each day takes at least 15 minutes to record, warns that data quality can decline as days are added, and notes that recording itself changes what people eat, an effect called reactivity.
| Who asks | Window | Purpose |
|---|---|---|
| NHS renal dietetics | 3 days, 1 at a weekend | Nutrition and fluid before clinic |
| Specialist dietetic consult | 7 days before the visit | Intake before a FODMAP plan |
| Research assessment | 1 or 3 days, sometimes repeated | Usual intake estimate |
If nobody told you how many days, ask.
What should I write down for each meal?
Write the date, the time, the food and the amount. Amount is the part a clinician cannot reconstruct later. The NHS renal leaflet asks for weights or household measures where possible, and the National Cancer Institute allows portions estimated from pictures or food models.
In Diabetic Medicine in 2010 (PMID 20536499), 102 children aged 8.3 to 18.1 and 110 caregivers estimated the carbohydrate in 17 standardized meals of 8 to 90 g. 73% of the 2,530 estimates fell within 10 to 15 g. The misses are the lesson: individually labeled foods were most often right, core foods in non-standard quantities most often wrong, large meals underestimated and snacks overestimated.
Those were children and caregivers counting carbohydrate, not adults counting calories: a pattern, not a law. Where a label exists, the amount can be copied rather than judged by eye.
Labels carry a legal tolerance of their own. Under 21 CFR 101.9, a tested sample need only reach 80% of the declared value for naturally occurring carbohydrate, protein, fiber and micronutrients, and may not exceed declared calories, sugars, fats or sodium by more than 20%. Everyday logging precision is covered on how close to your calorie target you need to be.
What the record needs to carry
What clinicians ask forCan I use a photo estimate to work out an insulin dose?
No. An AI photo estimate is never an appropriate input to an insulin dose. For a mealtime dose the carbohydrate figure comes from the label or a measured portion, and from the insulin-to-carb ratio your clinician set with you. The American Diabetes Association describes that sequence.
The CDC states the mechanism: people on mealtime insulin count carbohydrate to match the dose to the food. The American Diabetes Association names the 2 label elements, serving size and grams of total carbohydrate, and the insulin-to-carb ratio that turns them into a dose. NIDDK puts that plan in the hands of your health care team.
In Diabetic Medicine in 2009 (PMID 19317823), 31 children and adolescents ate meals built around 60 g of carbohydrate. A 10 g variation either way changed neither blood glucose nor the glucose curve over 2.5 hours. The 70 g meal ran up to 1.9 mmol/l higher at 3 hours, still inside international post-meal targets. That is 1 small study, and it changes no one's dosing. The plan to follow is the one your own clinician set with you.
In the Journal of Diabetes Science and Technology in 2025, Baumgartner and colleagues compared 53 adults with type 1 diabetes against 2 apps: the people averaged 21 g of absolute error, one app 24 g, and SNAQ 13.1 g. The authors still wrote that its impact on glucose control remains to be evaluated, and the senior author consults for SNAQ. Unproven is the accurate word, not inaccurate.
CalorieCounter is unreleased and cannot be installed yet. It is not a medical device, and a photo estimate of a meal, from it or any other app, does not belong in an insulin calculation.
Why can't a food app tell me my potassium and phosphorus?
Because US labels do not have to carry phosphorus. 21 CFR 101.9 makes vitamin D, calcium, iron and potassium mandatory on the Nutrition Facts panel, and lists phosphorus only among nutrients a manufacturer may declare voluntarily. A database built from packaged labels inherits that gap.
21 CFR 101.9 makes vitamin D, calcium, iron and potassium the mandatory mineral declarations. Phosphorus sits in the voluntary table, at a Daily Value of 1,250 mg, and the same paragraph bars any nutrient outside those lists from the panel. So a potassium figure usually exists for a packaged food, a phosphorus figure often does not, and no app can publish what the manufacturer never did.
The renal targets come from a person. NIDDK says there is no single meal plan for everyone with chronic kidney disease. It gives no more than 2,300 mg of sodium a day as the general limit, says many people with CKD need less, and leaves the figure to their clinician. For potassium it prints no number and points to a dietitian. For phosphorus it describes binders taken with meals as the disease advances. NIDDK's hemodialysis guidance adds fluid, and flags processed and packaged foods as especially high in phosphorus.
What should I track for blood pressure?
Sodium, and mostly the sodium you buy rather than the sodium you add. The 2025 to 2030 Dietary Guidelines for Americans set the limit at less than 2,300 mg a day for everyone aged 14 and over. The CDC puts average US intake above 3,300 mg.
The same Dietary Guidelines for Americans set lower limits for children: 1,200 mg at ages 1 to 3, 1,500 mg at 4 to 8, 1,800 mg at 9 to 13. For blood pressure, the NHLBI DASH eating plan runs 2,300 mg as standard and 1,500 mg as a lower target, which it says lowers blood pressure further without quantifying by how much.
Where the sodium already sits changes what is worth logging. The CDC says most of it comes from processed and restaurant foods, without publishing a split. The UK figure is published: the NHS sets the limit at 6 g of salt a day, about 1 level teaspoon, and says around three quarters is already in packaged and everyday foods such as bread, cereals and ready meals. A record that captures the pinch at the stove but skips the bread and the takeaway measures the wrong end.
What does an IBS clinic want in a diary?
Food and symptoms recorded together, not a calorie total. NHS advice is to keep a diary of what you eat and any symptoms you get, then avoid what triggers you. The tracked variable is a symptom, so no nutrient number answers the question on its own.
The NHS page on diet, lifestyle and medicines for IBS points to a GP, then a dietitian or specialist, when diet changes and pharmacy medicines do not help.
NICE clinical guideline CG61 puts first-line management at regular meals, at least 8 cups of fluid a day, tea and coffee held to 3 cups a day, fresh fruit limited to 3 portions a day of roughly 80 g each, and avoiding sorbitol where diarrhea dominates. None of that is a calorie count.
NICE recommendation 1.2.1.8 places the low FODMAP diet second, and says it should only be given by a healthcare professional with expertise in dietary management. It also has an end: the Monash-authored implementation paper describes 3 stages, restriction, reintroduction and personalization, with short-term dietetic follow-up framed as 2 to 8 weeks after the first appointment. The same paper cites a retrospective review of 80 patients in which patient-led implementation was linked to more than double the FODMAP intake during restriction, a look back rather than a trial.
What do I track for gestational diabetes?
Blood glucose first, with food timing and amounts around it. NICE guideline NG3 tells clinicians to teach self-monitoring and to refer every woman with gestational diabetes to a dietitian. It sets numeric glucose targets. It sets no carbohydrate gram target at all.
| Measurement | NICE NG3 target |
|---|---|
| Fasting | 5.3 mmol/l |
| 1 hour after a meal | 7.8 mmol/l |
| 2 hours after a meal | 6.4 mmol/l |
| Taking insulin, lowest safe level | Above 4 mmol/l |
NG3 also sets who tests what: women managing with diet and exercise alone test fasting and 1-hour post-meal glucose daily. The CDC describes the daily version as checking blood sugar and eating the right amounts at the right times, with insulin or metformin added if that is not enough.
One number runs the other way. A 2025 systematic review from the Agency for Healthcare Research and Quality records the RDA for carbohydrate in pregnancy as 175 g a day at any age, set by the Institute of Medicine in 2005 from 100 g for the maternal brain plus 35 g for the fetal brain. The review notes evidence pointing to at least 220 g a day; the official RDA stays at 175 g. It is the one figure here that works as a floor, not a ceiling. Which number applies in a given pregnancy is the clinician's call.
What changes after bariatric surgery?
The record becomes protein and fluid, with a timing rule attached. The 2019 AACE and ASMBS guideline sets a minimum of 60 g of protein a day, rising to 1.5 g per kg of ideal body weight, and more than 1.5 liters of fluid daily, kept away from meals.
Recommendation 38 of the 2019 AACE and ASMBS perioperative nutrition guideline puts protein at 60 g a day as the floor, up to 1.5 g per kg of ideal body weight as the usual ceiling, and up to 2.1 g per kg case by case, individualized and guided by a registered dietitian. Recommendation 40 covers fluid: more than 1.5 liters a day, taken slowly, preferably at least 30 minutes after meals to prevent gastrointestinal symptoms.
Both carry a Grade D, the weakest evidence grade in that document, so they are an agreed standard rather than a measured optimum. The European Association for the Study of Obesity gives the same 60 g floor and the same 1.5 to 2.1 g per kg range. The much-cited ASMBS 2016 update does not hold the protein figure: it covers micronutrients only.
Write the times as well as the amounts: a daily total cannot express a 30-minute gap.
How do I hand the record over?
Bring the whole window, dated, with amounts, and bring it as it happened. Keep recording on the day that went badly, because a tidied diary hides what the clinician is reading for. Ask the clinic in advance whether they want paper, a file, or a screen.
Reactivity cuts both ways: recording changes what people eat, and the same pull makes people edit afterwards. A smoothed diary is worth less than a short one.
What to carry, at minimum:
- Every day of the window, dated, including the day you would rather leave out.
- Times, not just meal names. Breakfast at 6 and breakfast at 11 are different facts.
- Amounts in weights or household measures, plus label figures for packaged foods.
- Drinks and water, which the renal leaflet counts in.
- Symptoms or insulin doses, if the clinic asked for them.
CalorieCounter is unreleased and cannot be installed yet. Its export is on the free plan and covers what you logged. Every figure here carries the same instruction: the plan is set with your own clinician, and the record informs that conversation rather than replacing it. Where an app total and the plan disagree, the plan wins.
FAQ
Is a longer food diary better?
Usually not. The National Cancer Institute lists declining data quality as the number of recorded days rises, and the tendency to eat differently while recording. A complete 3-day record beats a patchy 2-week one. Ask which window the clinic wants.
Do I have to weigh everything?
No. Weighing is one option among several. The National Cancer Institute lists food models, pictures and other visual aids alongside scales, and the renal leaflet accepts household measures. Weigh where the figure drives a decision, such as a mealtime insulin dose, or where a portion has no label.
My clinic asked for a food diary but I already track in an app. Is that enough?
Often yes, if it covers the exact days requested and records amounts rather than only daily totals. Hand it over unedited, then add what the clinic asked for that a food log does not hold: symptoms, fluid volumes, medicines or glucose readings.
Sources
- Hull University Teaching Hospitals NHS Trust: Renal Food Diary patient leaflet
- National Cancer Institute: Food Record at a Glance, Dietary Assessment Primer
- Sultan et al., How to Implement the 3-Phase FODMAP Diet Into Gastroenterological Practice, J Neurogastroenterol Motil 2022
- CDC: Carb Counting, Diabetes
- American Diabetes Association: Carb Counting and Diabetes
- NIDDK: Healthy Living with Diabetes
- Smart et al., Children and adolescents on intensive insulin therapy maintain postprandial glycaemic control without precise carbohydrate counting, Diabetic Medicine 2009 (PMID 19317823)
- Smart et al., Can children with Type 1 diabetes and their caregivers estimate the carbohydrate content of meals and snacks? Diabetic Medicine 2010 (PMID 20536499)
- Baumgartner et al., Carbohydrate Estimation Accuracy of Two Commercially Available Smartphone Applications vs Estimation by Individuals With Type 1 Diabetes, J Diabetes Sci Technol 2025
- eCFR: 21 CFR 101.9, Nutrition labeling of food
- NIDDK: Healthy Eating for Adults with Chronic Kidney Disease
- NIDDK: Eating and Nutrition for Hemodialysis
- US Departments of Health and Human Services and Agriculture: Dietary Guidelines for Americans 2025-2030
- CDC: About Sodium and Health
- NHS: Salt in your diet
- NHLBI: DASH Eating Plan
- NHS: Diet, lifestyle and medicines for IBS
- NICE CG61: Irritable bowel syndrome in adults, recommendations
- NICE NG3: Diabetes in pregnancy, recommendations
- AHRQ: Digestible Carbohydrate Intake and Maternal-Infant Outcomes, a systematic review (2025)
- CDC: Gestational Diabetes
- Mechanick et al., AACE and ASMBS clinical practice guidelines for perioperative nutrition in bariatric procedures, 2019 update
- Busetto et al., EASO practical recommendations for post-bariatric surgery medical management, Obes Facts 2018
- ASMBS Integrated Health Nutritional Guidelines 2016 Update: Micronutrients
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