Dietary intake assessment - Case scenarios

Choosing a dietary assessment tool

grapefruit slice

The following case studies have been developed to reflect situations in which nutritional data may be collected as part of child obesity research. In each study, the intent is to illustrate a process for selecting a diet assessment method. The information provided in each study is only sufficient to illustrate key considerations for various dietary assessment approaches and recommend the adoption of one or more methodology approaches (e.g. direct observation or food frequency questionnaire). Details of specific instruments are not provided, but suitable tools may be found in the database of dietary assessment tools.

Study 1: Nutrition intervention among pre-schoolers

Researchers plan to evaluate a 12-week program in pre-schools targeting fruit and vegetable consumption in 3-5 year olds. All pre-schools with children 3-5 years in a given area will randomly be assigned to either an intervention group or control group in the study. The intervention group will be provided with parental education, targeting the provision of availability of fruit and vegetables in the pre-schooler's home environment. The control group will be provided with information about availability of fruit and vegetables at the pre-school.

The aims of the study are to determine:

  1. Does an intervention which aims to increase the availability of fruit and vegetables in pre-schooler's homes through parental education increase childrens consumption of fruit and vegetables beyond that achieved through increasing availability at the pre-school level
  2. The availability of fruit and vegetables in the pre-schooler's home in each group in comparison to the availability in the pre-school.

In this case study situation, funding is limited, and so the intervention is assessed in a random sample of 110 children in each arm of the study (allowing for a 10% drop out following initial consent to participate). It has been determined that this number should be an adequate sample size to detect a change of 0.5 serves/day of fruit and vegetable intake, providing a reasonably robust dietary assessment method could be conducted.

Consideration is also given to whether the impact of fruit and vegetables intake on total diet and nutrient could be investigated, but it was decided this would beoutside the study scope and resources. Focus is to be on robust, quantitative measure of single foods (fruit and vegetables) and their availability.

Dietary methods selection process

The following factors were considered in selecting study dietary assessment tools:

  • Resources were available for (objective) in home and in pre-school data collection
  • Children were too young to report intake so there was a reliance on parent report, however children also spent time at pre-school so parent report only was limiting
  • Multiple instances of fruit and vegetable intake across a day (limits direct observation for primary outcome)
  • Limited pre-school or parent time for data collection (need low participant burden)
  • Usual intake at group level considered acceptable
  • Need to detect change over 12 weeks (recall period important).

Seven methods were considered as they would provide information on intake of whole food/s. Four were eliminated based on participant burden and excess information collected (ie more suited to total diet).

A combination of diet assessment methods was selected:

  • Childrens fruit and vegetable intake (primary outcome) will be assessed using a parent-reported FFQ previously validated in a similar population
  • Complemented with an objective measure of fruit and vegetable availability in the home and pre-school using direct observation. An alternative measure to direct observation was considered, in relation to collection of purchasing receipts of fruit and vegetable items, but this was considered potentially intrusive for the parents
  • In order to assess availability at the pre-school, a review of menus and direct observation was undertaken at baseline and 12 weeks.

Study 2: Clinical weight management program for adolescents

A community health centre run a 6-month group weight management program for adolescents four times a year. Approximately 12 adolescents attend a 60 minute session once a month (n=48 per year). Feedback on progress is incorporated as a behaviour change technique into the group sessions. Currently this is only based on weight results. Facilitators would like to expand this focus to provide feedbacks on the lifestyle behaviours the adolescents are changing during the program in order to facilitate gradual weight loss.

The aims of the study are to determine if a weight management program for adolescents can:

  1. Reduce intake of intake of non-core foods, portion size, water consumption andfruit and vegetable intake
  2. Reduce entertainment sedentary activity and increase opportunities to be active.

Dietary methods selection process

The following factors were considered in selecting the diet assessment methodology;

  • High risk of under-reporting given an overweight and adolescent population
  • The need for low participant and facilitator burden (limited time in sessions, need to utilise to provide on the spot feedback)
  • Low research budget.

A questionnaire or diet/activity checklist approach was considered. A 5-minute questionnaire approach was chosen so that facilitators and barriers to lifestyle change could also be explored. Where possible questionnaire items were adapted from validated questionnaires. As part of a dietetic student placement, the questionnaire will be validated against a measure of total diet.

Study 3: Population based obesity prevention program among schools aged children

In a large scale, population based program, practitioners are working in partnership with primary schools across a regional area to encourage healthy and active lifestyles. Strategies target food behaviours associated with childhood obesity including increasing fruit and vegetable consumption, water intake and decreasing energy-dense nutrient-poor snacks, sweetened drinks and meals eaten in front of television. While all schools in the region are included in the program, a representative random sample is to be selected for a pre and post evaluation. This evaluation will occur at both the school environment and individual level and examine whether the program strategies led to changes in both the selected behaviours and the school environments that support healthy lifestyles.

The aims of the study are to determine:

  1. If an in-school intervention can change food related behaviours
  2. Is an in-school environment more supportive of a healthy lifestyle.

Dietary methods selection process