Portion size estimation in dietary assessment: a systematic review of existing tools, their strengths and limitations

Abstract Context Overestimation or underestimation of portion size leads to measurement error during dietary assessment. Objective To identify portion size estimation elements (PSEEs) and evaluate their relative efficacy in relation to dietary assessment, and assess the quality of studies validating PSEEs. Data Selection and Extraction Electronic databases, internet sites, and cross-references of published records were searched, generating 16 801 initial records, from which 334 records were reviewed and 542 PSEEs were identified, comprising 5% 1-dimensional tools (eg, food guides), 46% 2-dimensional tools (eg, photographic atlases), and 49% 3-dimensional tools (eg, household utensils). Out of 334 studies, 21 validated a PSEE (compared PSEE to actual food amounts) and 13 compared PSEEs with other PSEEs. Conclusion Quality assessment showed that only a few validation studies were of high quality. According to the findings of validation and comparison studies, food image–based PSEEs were more accurate than food models and household utensils. Key factors to consider when selecting a PSEE include efficiency of the PSEE and its applicability to targeted settings and populations.