1. XNN001 Population nutrition and physical
activity assessment

2.  Usual intake more important than one day snapshot
 Methods of measuring dietary intake include
◦ Diet History
◦ 24hr recall
◦ Food frequency questionnaire
◦ Food diaries
◦ Duplicate meals
 Used to investigate quality of diet (core-foods) and
energy intake

3.  Present/prospective
◦ Diaries
 Household measures
 package weights
 numbers of items
 size of items
 Weights
◦ Chemical analysis
 Duplicate meals
 Past/retrospective
◦ Actual
 24-hour recall
 Food Frequency
Questionnaires
◦ Usual
 Dietary Histories

4. Prospective (current)
Retrospective(past)
• Actual
• 24-hour recall
• Food Frequency Questionnaires
• Usual
• Dietary Histories
•Food diaries
• Household measures or weighed
•Chemical analysis
•Duplicate meals

5.  Current diet: Heisenberg uncertainty principle:
as soon as you stop something to measure it you
change the behaviour
 Past diet: relies on memory, conceptual and
cognitive ability and honesty on part of
respondents
 No direct measure of what people eat will
provide a true picture of their dietary habits
 Task is to understand and define the errors,
try to minimise, manage statistically and
incorporate in interpretation of results.
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6.  Is information needed about foods, nutrients, other
food constituents, dietary behaviours (eg eating
meals)?
 Is the average intake of a group required?
eg. do Australian Vietnamese babies have lower iron
intakes than Caucasian Australian babies
 Is the average intake of each individual needed ?
eg is iron intake of Australian Vietnamese babies
related to the prevalence of anaemia in this group.
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7.  Using household measures
◦ Set time period for recording (minimum 3 days)
◦ Record all food consumed & drink over there days in
diary
◦ Include a non-working day
 Using weights
◦ Similar recording to above but use a set procedure
for weighing using scales & measuring utensils

8.  Requires the participant
to record food and
drink eaten and
estimate the amount

9.  supplement use recorded
 number of days varies, traditionally 7, 3 or 4
consecutive days, including a weekend day for 3/4 day
records
 number of days required can be determined statistically
and depends on the nutrient of interest, objective of
the study etc
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10.  Potential to provide quantitatively accurate
information on food consumed during
recording period
 ‘Gold-standard’
 Less likely for foods to be omitted
 Accuracy of portion sizes
 Information RE meal patterns and specific
foods
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11.  Motivation and high levels of literacy
required
 High respondent burden
 Change in intake (result of monitoring)
 Bias in representativeness of respondents
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12.  Gold standard’ status now questioned
(systematic under reporting)
 major issue is how representative the
recording period is of ‘usual’ diet, apart from
the issues of reporting errors. ie natural
variation in diet.
 high coding burden, especially in large studies
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13.  Observed or plate waste method
◦ respondent researcher burden
◦ under reporting
 Estimated portions
◦ hh measures, plate pictures, food models, photos –
mobile phones
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14.  Collection of an identical
meal/food from client for
analysis
◦ useful for analysing food
composition
 Limitations
◦ expensive & time consuming
◦ impractical outside confined
setting

15.  Ask individual to remember what food &
drinks they have consumed in previous 24
hours or day
◦ usually performed by trained interviewer
Let’s try a 24-hour recall
1. Write down on a piece of paper what you have eaten in
the last 24 hours
2. Do you think there is sufficient detail for you to
analyse it in detail?
3. Do you think you have been completely honest?
4. Could you remember exactly?
5. Could you estimate quantities accurately?
6. Do you think this record is typical for you?

16.  Low respondent burden
 Quick, inexpensive
 Low levels of literacy required
 Potential for greater representativeness
 Does not change dietary habits as
retrospective
 Coding easier
 Provide some information on meal patterns/
intake of specific foods
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17.  relies on memory
 portion estimation
 relies on interviewer skill, potential for observer bias
 can only provide group means, assess proportion of
population with adequate/inadequate intakes
 does not provide data on usual intake of individual, no day to
day variation – repeat recall 10%
 multiple 24h recalls have been used to provide usual intake
of individuals.
Criteria used to decide no of days of records apply
non-consecutive days, no subject notice
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18.  Qualitative & semi-quantitative
survey of:
◦ how often foods are eaten +/- how much
◦ usually self administered, can be interview
◦ general or specific FFQ
 Developed to be used for large groups
Information about usual food consumption patterns

20.  3 sections:
(i) food list
(ii) frequency of use categories
(iii) estimates of quantities usually consumed
 May be administered by self (post),
interviewer and now often optically
scannable
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21.  Estimates usual intake of foods
 Rank individuals according to their usual
intake of foods or groups of foods (and
nutrient intake if portion sizes included)
 Widely used
 Generally not adequate to estimate absolute
intake
 Can behave unpredictably in subpopulations,
must be validated for study population
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22.  Easy and cheap to self administer
 Avoids observer bias
 Suitable for geographically widespread
sample as can be done by telephone or post
 Small burden for respondent
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23.  Cannot use FFQ designed in US here, even UK
to here difficult, adult FFQ cannot be used
for children or adolescents
 No information on food intake and meal
patterns;? use supplementary questions
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24.  Amount of work required to develop and validate
 Quantification of intake not as accurate as
recalls/records.
 Errors
 incomplete listing of foods
 errors in frequency estimation
 errors in portion size estimation
 Memory and period of recall required has major
issues eg 12 months, three months etc.
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25.  Seasonal variation difficult to capture eg
mangoes
 Tend to overestimate, particularly fruit and
vegetable intake
 Cognitive difficulties with reporting foods eaten
alone and in combination, risk of double counting
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26.  Foods grouped (eg beefburgers, steak, steak
pie) - assumptions made on contribution each
food makes to the overall reported
frequency and portion size
 FFQ designed for one ethnic group are
unlikely to be suitable to others due to
major differences in food types, recipes,
food combinations & frequency
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27.  Requires nutritionist to
interview participant
and to record detail and
estimate the quantities
of usual/ typical intake
Original adaptation - 3 components
1. a usual 24-hour recall
usual takes away atypical errors
food amounts enhanced by using food models
2. a checklist
3. a short (3 days) diary

28.  Original methodology more commonly now adapted -
Multiple variations
 An investigation of habitual intake over a
specified period of time – usually 1 mo to 1 yr
 24 hour recall + variations
 Details on types (e.g. low fat), quantities,
brands)
 Indicates patterns of eating
 Able to estimate energy, macro & micro
nutrients
 Able to estimate food groups
 Can be targeted to particular nutrients e.g.
carbohydrate in diabetes
 Administered by a trained health professional

29.  a usual 24-hour
recall
◦ would you normally
consume breakfast?
◦ what would you
normally have?
◦ what type of bread
would that usually
be?
◦ etc

30. CHECKLIST
 bread, cereal, rice, pasta, biscuits, crackers
 vegies, fruit, juices
 meat, offal, poultry, fish, seafood, eggs, legumes
 milk, cheese, yoghurt, ice cream, milk drinks
 butter, marg, oils, dressings
Miscellaneous:
 soups, gravies, sauces, pickles, sugar, jam, honey, p/butter,
vegemite
 cakes, desserts, lollies, chocolates
 snack foods, nuts, chips, munchies
 soft drinks, cordials, water
 alcohol
 weekends, take-away, eating out
 salt
 supplements (vit/min/fibre)
 cooking methods etc

31. DietHistoryExample

32.  honesty, memory & frankness of client
 need highly skilled interviewer
 expensive & time consuming
 may underestimate intake
Most useful information for
assessment

33.  Depends on memory
 Bias towards those with regular meal intake
and pattern
 Exaggeration of meal regularity
 Underestimation of snacks
 No indication of day to day variability
 Requires highly trained and skilled staff -
high risk of interviewer bias
 More likely to recall immediate past than
period of interest
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34.  Single interview gives detailed information on meal patterns,
food consumption, usual nutrient intake
 Information on usual intake over long periods can
theoretically be obtained
 Particular attention can be given to nutrients of interest and
goods/ drinks that are often under reported eg alcohol,
confectionary
 Detailed food preparation can be obtained
 Seasonal variation can be assessed
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35.  duplicate portion methods
 PETRA (Portable Electronic Tape Recorded
Automatic) Scales - linked scales & tape recorder
 photographic methods - atlas of photographed
food potions
 video recording of meals – use of mobile phones
 computer assisted automated diet histories/ 24
hour recalls
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39. 39

40. Respondent bias
 inaccurately report income and age
 over report consumption of ‘good foods’
 under report ‘bad’ foods - alcohol, snack
foods, confectionary etc
 overweight respondents may under report
total food intake
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41.  Respondent memory lapses
 Incorrect estimation of portion size
◦ concept of ‘average’ serving size differs
◦ weighed vs estimated does not seem to introduce
bias
 Daily variation
in one respect not an error but does introduce
misclassification
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42. Supplement usage
 fail to record gives underestimation of nutrient
intake
Frequency food consumption
 FFQ tend to overestimate intake, especially fruit
and veges
 No. of food items can have an effect, shorter list
tends to increase bias associated with estimation
of single food items
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43.  Certain groups, eg overweight, systematically under
report their habitual food intake; diabetics tend to
report prescribed diet
 Recently identified problem that has called into
question the ‘gold standard status’ of the 7 day
weighed food record.
 Must demonstrate if present/not
 Must identify under-reporters for analysis
 ? Exclude, depends on aims
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44. Day of the week affect
 significant week/weekend day differences for
some foods and nutrients
 likely to be culturally and economically
significant and change over time
 need to proportionately represent weekend
days in design
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45. Seasonal effects
 can be very specific especially in developing
countries and poor communities
 variation tends to be greater for foods than
nutrients
 some micronutrients significantly effected by
fruit and vegetable consumption
 survey across seasons if possible
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46.  Essential to help understand the relationship between
what we have measured and the ‘truth’
 Describe and quantify error as far as possible to enable
consideration in
analysis
interpretation of results
 To ensure the tool will allow us to detect the diet
disease relationship should it exist
 Inadequate attention to validation results in wasted
resources and failure to detect true relationships
between diet and disease`
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47. Reliability
 reproducibility; repeatability
 if we did it again would we get the same answer
 measure reliable but not valid; if valid must be
reliable
Validity: are our findings true?
 requires a true external reference measure or
standard
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48.  Not possible to have absolute direct measure
of dietary intake, ie errors in all methods
 aim to establish ‘relative validity’
 compare test method with reference method
 does not necessarily indicate method valid, may
indicate both methods have the same errors
 Relative validity major issue in nutritional epi
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49.  validity and reproducibility of reference method
should be high
 7 day record has been the classical reference
method - not error free
 errors should be independent
eg recall method validated by prospective method
eg FFQ against Diet history -can reflect same
exposure period but both rely on portion size and
frequency estimations and recall skills
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