Background & aims: Image-assisted or image-based dietary assessments (IBDAs) refer to the use of food images as the primary dietary record and have emerged as key methods for evaluating habitual dietary intake; however, the validity of image-assisted or IBDAs is still unclear, and no meta-analysis has been conducted. Our aim was to investigate the validity of IBDAs in assessing energy intake (EI) and macronutrients compared to biomarker-based (double-labeled water (DLW)) and traditional methods of 24-h dietary recall (24-HDR) and estimated/weighed food records (WFRs). Methods: A systematic review and meta-analysis were performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines using the PubMed, EMBASE, and Cochrane Central Register of Controlled Trials databases. Of the 4346 papers identified, 13 studies met the inclusion criteria, comprising 606 participants. Results: The overall weighted mean difference (WMD) in EI showed significant under-reporting (WMD = −179.32 kcal, 95% confidence interval (CI): −269.50 to −89.15 kcal; I2 = 89%), with the greatest difference observed between tests and DLW (WMD = −448.04 kcal, 95% CI: −755.52 to −140.56 kcal; I2 = 95%). A small non-significant trend towards under-reporting of carbohydrates (CHOs) was observed (WMD = −9.17 g, 95% CI: −20.58 to 2.24 g; I2 = 64%), but no differences were found in protein (WMD = −0.08 g, 95% CI: −3.94 to 3.79 g; I2 = 68%, p <0.01) or fat (WMD = −0.57 g, 95% CI: −2.58 to 1.43 g; I2 = 12%, p = 0.35). A meta-regression analysis found potential effects of the body-mass index (tests vs. DLW: β = 34.9, p = 0.063) and duration of the assessment (tests vs. WFR: β = −66.5, p = 0.002) on EI; age (tests vs. 24-HDR: β = −2.222, p = 0.019) and duration of the assessment (tests vs. WFR: β = −9.19, p = 0.013) on CHO intake; duration of the assessment on protein intake (tests vs. WFR: β = −3.2250, p = 0.0175); and duration of the assessment on fat intake (tests vs. WFR: β = −1.07, p = 0.040). Conclusions: Except for DLW, no statistical difference was found between IBDAs and traditional methods. This suggests that like traditional methods, image-based methods have serious measurement errors, and more studies are needed to determine inherent measurement errors in IBDAs.
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