explored associations between diets and undernutrition, with less attention given to the full range of malnutrition outcomes. While the nutrition transition is often more advanced in middle-income countries, the pace of change and the impact in low-income countries cannot be overlooked (Popkin, Corvalan, and Grummer-Strawn 2020). Food consumption patterns vary widely across geographic regions, with big differences between regions in terms of insufficient intakes of healthy foods and excess intakes of unhealthy foods (Miller et al. 2022). Spatial variation in dietary patterns (Zhao et al. 2022) and dietary diversity (Alemu et al. 2022) also occur within the same country. Therefore, it is important for all countries to have evidence based on their local context.

Our scoping review also revealed the polarization in evidence in LMICs. One group of studies focused on the foods that matter for achieving nutrient adequate diets in environments where there are still widespread nutrient inadequacies and undernutrition, especially among nutritionally vulnerable individuals like young children and pregnant women. Another group of studies explored the foods that matter for preventing the rapid rise of overweight/obesity and NCDs with a focus on adult population. For the latter group, although all the SRM reviewed included at least one LMIC, the evidence was heavily weighted toward research conducted in highincome countries. The results of our review show the gaps in evidence for foods and dietary measures that can monitor multiple subconstructs of healthy diets in low-income country contexts, including nutrient adequacy, diversity, balance and moderation (Verger et al. 2023). This is an area of ongoing work to develop, validate and use more widely healthy diet metrics that concurrently capture these two sides of the DBM and are feasible to operationalize in LMICs taking a full life cycle approach.

By relying on meta-analyses for effect size estimates, our review also did not capture emerging approaches to assessment of unhealthy diets and associated outcomes that may be well-suited to monitor the rapid nutrition transition faced by several countries. For example, two relatively new metrics, the Global Dietary Recommendations Score (Herforth et al. 2020) and Global Diet Quality Score (Bromage et al. 2021), have been validated in several countries and are increasing in use in LMICs (Angulo et al. 2021; H. Wang et al. 2022; P. H. Nguyen et al. 2023). Both approaches utilize two sub-scores to monitor dietary factors protective against NCDs and those associated with increased risk of NCDs.

The results of our study provide an overview of the effect sizes for some of the dietary ‘culprits’ in both highincome and LMIC contexts. While consumption of UPF was not historically a major concern, the average dietary share of UPFs has already reached over 50% of total energy intake in some high-income countries and consumption of these foods has been rising quickly in LMICs over the past 30 years (Scrinis and Monteiro 2022). The summary of effect size ranges from SRM that include data from LMICs provide a starting point for better understanding what links exist and how these could be used to inform modeling assumptions on the nutrition and health costs associated with unhealthy diets in LMICs.

No meta-analysis for UPF as a risk factor for overweight/obesity in children <5 years was found in our search, however. UPF consumption among young children has been an active area of investigation and there are several systematic reviews of observational studies. For example, Pries and colleagues (2019) conducted a systematic review of snack food and SSB intake and nutritional status of children 0-23 months in LMICs, noting mixed results, with only one of three studies reporting a positive association with overweight. Two other systematic reviews also explored the risk of obesity (De Amicis et al. 2022) and body fat (Costa et al. 2018) associated with UPF consumption in children. In a group of 26 studies (15 with cohort design) that assessed groups of UPF (e.g. snacks, fast food, junk food) or specific UPF (e.g. SSB, sweets, ready-to-eat cereals), most reported positive associations between UPF consumption with body fat (Costa et al. 2018). However, De Amicis and colleagues (2022) found in their systematic review that consumption of UPF was positively associated with obesity/adiposity only in four longitudinal studies in children with four or more years of follow-up but not in cross-sectional studies. They suggest that a consistent intake of UPF over time may be needed to have an impact on the nutrition status of children.

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