Validation of Two Portion Size Estimation Methods for Use with the Global Diet Quality Score App

Area of Science:

• Nutrition Science
• Dietary Assessment Methods
• Public Health Nutrition

Background:

• The Global Diet Quality Score (GDQS) is vital for assessing diet quality.
• Standardized portion size estimation is crucial for accurate GDQS data collection.
• The GDQS app utilizes 3D cubes, with playdough proposed as an alternative.

Purpose of the Study:

• To validate the GDQS app using 3D cubes and playdough against weighed food records (WFRs).
• To assess the equivalence of GDQS measurements obtained via app (cubes/playdough) and WFRs.
• To evaluate the agreement in classifying individuals at risk of poor diet quality.

Main Methods:

• A repeated measures design involved 170 participants aged 18+ years.
• Participants estimated portion sizes using WFRs and the GDQS app with cubes and playdough.
• Equivalence was tested using paired two one-sided t-tests (TOST) with a 2.5-point margin; agreement quantified by Kappa coefficient.

Main Results:

• GDQS measurements from cubes and playdough were equivalent to WFRs within the 2.5-point margin (p=0.006 for cubes, p<0.001 for playdough).
• Both cubes (κ=0.5685) and playdough (κ=0.5843) showed moderate agreement with WFR in identifying individuals at risk of poor diet quality.
• Substantial agreement was found for 22 out of 25 food groups, with liquid oils showing the lowest agreement (κ=0.059).

Conclusions:

• The GDQS app, whether using 3D cubes or playdough, provides equivalent diet quality assessments compared to WFRs.
• These findings support the use of simplified, validated tools for dietary assessment.
• This facilitates more frequent and accessible evaluations of population diet quality.