Background In low- and middle-income countries (LMICs), food insecurity has traditionally been associated with undernutrition. However, as many LMICs undergo a rapid nutrition transition, greater access to inexpensive, energy-dense, and nutrient-poor foods is contributing to rising rates of overweight and obesity. These shifts may be altering the relationship between food insecurity and excess weight, a link that has been more widely documented in high-income countries. This systematic review aims to synthesize evidence on the association between food insecurity and overweight/obesity among adults in LMICs, and to identify proposed mechanisms and contextual factors that may influence this relationship.

Methods Primary observational studies focused on the association between food insecurity and overweight/obesity among adults in LMICs will be systematically searched from multiple electronic databases, including PubMed, EMBASE, Global Health, Scopus, and LILACS. Grey literature will be explored using Google Scholar and ProQuest Dissertations & Theses Global. Reference lists of included studies and relevant reviews will also be manually screened to identify additional studies. Extracted data will include measures of food insecurity, overweight/obesity outcomes, and any reported mechanisms or contextual factors influencing their relationship.

Discussion This review will contribute to a deeper understanding of the complex and evolving relationship between food insecurity and overweight/obesity in LMICs. Where data allow, we will explore how this association varies across country income levels, urban and rural settings, sex, age groups, and exposure to extreme events. Identified mechanisms and contextual modifiers will be synthesized to provide insights into the pathways that may underlie these associations. The findings will help identify knowledge gaps and inform future research and policy efforts aimed at addressing the dual burden of malnutrition in LMICs.

Registration This systematic review protocol is registered in PROSPERO under the registration number: CRD420251076653.

The authors have declared no competing interest.

This study is supported by Bloomberg Philanthropies. The funder had no role in the development of the protocol, including the study design, data extraction strategy, analysis plan, or decision to submit for publication.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

This study is a protocol for a systematic review and does not involve the generation or analysis of primary data. All data used will be obtained from previously published studies.