Diet surveys: 24-hour recall, food frequency and weighment
Diet surveys measure what people eat: by recall, food frequency, weighment or diet history. Family intake is divided by consumption units to compare with requirements.
Methods of diet survey
| Method | How it is done | Advantages | Limitations |
|---|---|---|---|
| 24-hour recall | Interviewer asks the person (or mother) to recall all foods and drinks of the past 24 hours, using standard cups and spoons to show amounts | Quick, cheap, low burden; suits large groups and people who cannot read | Depends on memory; one day may not be typical; amounts are estimates |
| Food frequency questionnaire (FFQ) | Person says how often each food on a list is eaten: daily, weekly, monthly, rarely | Shows habitual pattern; links diet with disease; quick | List may miss local foods; amounts rough; not exact nutrient intake |
| Weighment | Investigator weighs all raw foods used by the family, usually for 7 days, plus leftovers and waste | Most accurate | Slow, costly, needs trained staff; the family may eat differently while watched |
| Diet history | Detailed interview on usual eating over a long period, often with a recall and a food list | Shows long-term habits | Needs a skilled interviewer; long |
| Food inventory | Food in stock at the start and end, plus purchases, recorded over a period | Useful for hostels and institutions | Needs literate cooperation; waste hard to account for |
| Expenditure method | Family's spending on food is recorded | Cheap for large surveys | Rough estimate only |
Activity: conducting a 24-hour recall and an FFQ
- 1Prepare the forms: a recall sheet (time, meal, dish, ingredients, amount) and an FFQ list of local foods with frequency columns.
- 2★Carry standard cups, ladles, glasses and spoons of known volume so people can show how much they ate.
- 3Start from waking up yesterday and go meal by meal to bedtime, including tea, snacks and drinks between meals.
- 4Probe gently for forgotten items: oil, sugar in tea, pickles, fruit, street snacks.
- 5Convert cooked amounts to raw ingredients using the household recipe, then work out nutrients from the Indian Food Composition Tables (IFCT 2017, NIN).
- 6For the FFQ, read out each food and tick how often it is eaten; note the usual portion.
- 7★Compare intake with the ICMR-NIN 2020 requirement for the person's age, sex and activity, as a percentage.
★ one-way, controls the pace
Consumption unit coefficients (classic ICMR scale, as in Park)
Worked example: intake per consumption unit
In a 7-day weighment survey, a family used 9.24 kg of raw cereals (rice and wheat). The family: a father doing moderate work, a mother who is a sedentary homemaker, a son aged 10 and a daughter aged 4. Find the cereal intake per consumption unit per day.
- CUs: father (moderate) 1.2; mother (sedentary) 0.8; son, 10 years 0.8; daughter, 4 years 0.5.
- Total = 1.2 + 0.8 + 0.8 + 0.5 = 3.3 CU.
- Cereals used per day = 9.24 kg ÷ 7 = 1.32 kg = 1320 g/day.
- Per CU per day = 1320 ÷ 3.3 = 400 g.
- Each person's share = 400 g × his or her CU: father 480 g, mother 320 g, son 320 g, daughter 200 g. Check: 480 + 320 + 320 + 200 = 1320 g.
The family eats 400 g of raw cereals per consumption unit per day. Energy and protein are worked out per CU in the same way and compared with the need of one reference adult.
Consumption units and the 2020 requirements
The CU scale was built from energy needs, with the sedentary adult man as 1.0; older books took 1 CU as about 2400 kcal. The ICMR-NIN 2020 requirement for a sedentary reference man (65 kg) is about 2110 kcal/day. When you compare a family's intake per CU with a requirement, use the 2020 value and say which value you used.
In a village survey, a 24-hour recall is done in every sampled home, and a few homes are chosen for a 7-day weighment to check accuracy. Intake per consumption unit then shows whether the family's cereals, pulses and oil meet its members' needs.
2 marks: “What is a consumption unit?” A coefficient expressing each family member's energy need relative to a sedentary adult man (1.0 CU), used to work out per-head intake in family diet surveys.
5 marks: “A family has a moderately working father, a sedentary mother, a son of 10 and a daughter of 4, and uses 1320 g of cereals a day. Find the cereal intake per CU.” CU = 1.2 + 0.8 + 0.8 + 0.5 = 3.3; 1320 ÷ 3.3 = 400 g per CU per day.
10 marks: “Describe the methods of diet survey with their merits and demerits.” Table of 24-hour recall, FFQ, weighment, diet history, inventory and expenditure methods; steps of a 24-hour recall; consumption units with a worked example; comparing intake with ICMR-NIN 2020 requirements.
Recall = memory, FFQ = habit, weighment = accuracy. In the CU scale, the sedentary man is the '1'.