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Dietary assessment methods: What is a food diary?

Are you looking to use a food diary to monitor a patient’s food intake, or conduct a research study analysing nutrient intake? Or perhaps you’ve been asked to keep your own food diary and want to know why you should use it?

Previously, we wrote an article to help you decide which dietary assessment method to use.

In this article we’ll walk you through what a food diary is, why they are a useful method of recording diet, plus their strengths and limitations in comparison to other dietary assessment methods.

What is a food diary?

Let’s start with the basics – what is a food diary? Essentially, a food diary is a way of recording what someone’s had to eat and drink over the course of a day. To do this they keep a record, ‘a diary’, of everything they’ve consumed during the day – this a prospective dietary assessment method i.e. it does not rely on someone recalling what they’ve consumed after the event, it’s being recorded as and when consumed.

Typically templates for food diaries will include meal events including breakfast, lunch, dinner, snacks and drinks. Some may also include additional eating occasions such as a mid-morning snack or evening snack to act as a prompt not to miss any food and drink items consumed outside of the 3 main meals.

There should also be ample room for those completing their diary to fully describe what they’ve consumed – including as much information as possible to paint a complete picture of what they ate or drank. Details should include: the food itself, what brand it was, the portion size, cooking method used, time consumed and sometimes additional contextual information like where the food was consumed – was it at a restaurant, where they eating alone – this typically depends on what the aim of the food diary is.

For example a description like: ‘Breakfast: 7:30am – 2 slices of Hovis Best of Both bread toasted with Lurpak unsalted butter thinly spread’ provides far more helpful information than ‘Breakfast: toast with butter’. Having this level of detail is important later on when it comes to analysing the nutritional content of food items accurately.

There are two types of food diaries: weighed and estimated. As the name would suggest, weighed food diaries require each food and drink item to be weighed and measured to provide exact portion size values, whereas in the latter portion sizes are estimated. Whilst weighed diaries are the gold standard they aren’t the most practical method and as a result, food diaries typically use the estimated method.

Why are food diaries useful?

As mentioned, food diaries are a great way of recording comprehensive information about what someone has consumed and this can provide really useful insights into someone’s dietary habits, particularly if diaries have been completed on several different days. In order to accurately reflect what someone’s diet looks like, collecting food diary data on multiple days is advised – a minimum of 3 days including a weekend day is often recommended to capture the variation between the working week and weekend.

The rich information provided by food diaries provides opportunities for interventions and improvements to be made based on nutritional profiles, understanding dietary trends at both the individual and population level, and also making healthier choices as a result of increased awareness of nutritional content.

Estimating nutritional intake

Given that food diaries can provide rich data on dietary intake, this data can then be used to accurately calculate the corresponding nutritional intake of food and drink items using food composition tables or nutritional analysis tools like myfood24, particularly when used on several occasions to capture day-to-day variation in nutrient intake. Having accurate data on nutrient intake can: support the management of some diet-related conditions where nutrient monitoring is required; enable researchers to look at the effects of nutrient intake on health; or to evaluate the effectiveness of dietary interventions.

Understanding dietary trends

Food diaries can be a great way of unearthing dietary patterns and trends that may have otherwise have been missed, for example times of the day certain foods are being consumed, and how particular food items and/or meals contribute to overall nutrient intake. This can be a really useful insight when looking to make positive changes to the diet at an individual level or to study population-based trends.

Making informed choices

Food diaries can also be a helpful way for those keeping the diary to understand more about their own eating habits. Recording what is consumed and when can help increase their own awareness about the types and amounts of food they’re eating – this can help to identify triggers for eating and potential areas for change. Increasing the understanding of the nutritional content of food and drink items can help to make better and more informed food choices to improve overall dietary health.

Strengths and limitations of food diaries

Like all dietary and nutritional assessment methods, food diaries have strengths and weaknesses which should be considered before choosing which method to use.


  1. Food diaries provide detailed information on eating occasions and food intake including brand information, portion sizes as well as contextual information like location and time
  2. The detailed information provided can help to deliver an accurate estimate of short and long-term nutrient intake
  3. Not reliant on memory which may reduce recall bias and errors to improve the reliability of the results
  4. Day-to-day and seasonal variation can be captured when used on multiple days/occasions throughout the year


  1. Given that food diaries are often self-completed (although they can be completed on behalf of others) it requires the person completing the diary to be literate
  2. Those completing diaries must also be motivated to log items accurately and with the level of detail required which may be considered a burden
  3. Those completing diaries may also alter their eating habits to avoid recording their normal dietary intake or may simply misreport what was consumed
  4. Calculating the corresponding nutrient values can be time-consuming and complex if digital methods with inbuilt nutrient analysis, like myfood24, are not used

Using the myfood24 food diary to capture accurate diet and nutrient information

myfood24 is a quick and easy-to-use digital food diary solution that supports a variety of settings such as nutritional research and clinical use, developed with an evidence-based approach at the University of Leeds including biomarker validation.

Our innovative nutrition software has been designed to minimise the burden of completing food diaries as well as those analysing the food diary data e.g. a researcher or healthcare professional. This process starts with a simple user-interface built with smart prompts and features to support accurate recording including portion size images to enhance estimation. myfood24 has also been usability tested with a range of age groups to maximise ease of use.

Once a food diary has been submitted, myfood24 instantly calculates the corresponding nutritional content for each food item and for the total diary. Our automated approach removes the need for time-consuming nutritional analysis, myfood24 does the hard work for you! The comprehensive nutrient information is crafted into insightful reports – making exploration of the data quick and easy.

Underpinning the diet tracking platform is a unique food and nutrient database, regularly updated, containing over 92,000 food and drink items each with comprehensive nutrient information available for up to 117 nutrients. Unique data enhancements activities are conducted by our data team to minimise gaps to provide a more complete nutrient profile and accurate nutrient analysis. No other system has a database like this!

Try a free demo of the myfood24 food diary.

Key features of the myfood24 food diary

  • Users self-complete on a smartphone, tablet or computer – an offline version is also available
  • Simple and easy-to-use interface, users complete diaries in minutes!
  • Smart prompts and portion images support accurate recalls and ease of completion
  • Unique and robust food and nutrient database – choose from 92,000 food and drink products
  • Instant nutrient analysis on 117 nutrients – no coding required!
  • Evidence-based design and methodology
  • Validated against nutrient biomarkers by the University of Leeds

The myfood24 dietary analysis software is available in 7 different languages with 11 international food and nutrient databases, including for: France, Germany, the Middle East and USA. Find out about our international nutritional solutions.

Are you interested in using myfood24?

If you’re interested in using myfood24 you can use our contact form to send us a message or get in touch by clicking here

Still unsure if a food diary is the right method for you?

You can try a free demo of the myfood24 food diary or read our blog Which dietary assessment method should I use? for more information or check out our Dietary Assessment Methods series looking at 24 hour recalls and FFQs in more detail.

You can also visit Nutritools – a resource developed to support dietary assessment – who have released ‘Best Practice Guidelines’ to help researchers decide the most appropriate dietary assessment tool for their research.

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