PhD defence Diana Sagastume

The World Health Organization defines DBM as “the co-existence of undernutrition, including wasting, stunting, and micronutrient deficiencies, along with overweight, obesity, or diet-related non-communicable diseases, within individuals, households, populations, and across the life course”. On a broader scale, DBM reflects demographic and epidemiological transitions, and particularly the rapid nutrition transition occurring in many LMICs. Its underlying drivers span socio-demographic (e.g., poverty), biological (e.g., early-life exposure), environmental (e.g., food systems), and behavioral (e.g., lifestyle) factors. Given its wide-ranging health, social, and economic implications, international efforts have promoted the concept of double-duty actions (DDAs), which are interventions, programs, and policies that simultaneously address undernutrition and overnutrition. DDAs are grounded in the understanding that both forms of malnutrition share common underlying drivers, enabling dual benefits. Examples include scaling up programs to protect, promote, and support breastfeeding, as well as designing agricultural and food system policies to support healthy diets. As DBM is a relatively recent public health construct, evidence remains fragmented and limited. Its overall magnitude has yet to be systematically quantified in highly burdened regions such as LAC. Comprehensive epidemiological understanding, encompassing prevalence, temporal trends, and key associated factors, is also scarce, with this gap particularly evident in countries like Guatemala, where these determinants are likely context-specific. Moreover, evidence on the effectiveness and applicability of proposed DDAs for addressing DBM remains limited.

The research in this doctoral thesis addresses the following two research questions:
1.    What is the magnitude of household- and individual-level DBM across the LAC region, and specifically in Guatemala, and what factors are associated with its presence?
2.    What are the most influential factors of household-level DBM that can potentially be addressed through public health strategies in Guatemala?

Summary of thesis results
Chapter 2 presents a systematic literature review and meta-analysis conducted to quantify the prevalence of household- and individual-level DBM in the LAC region over the recent decades. Of the 754 records identified, 60 studies met the eligibility criteria, representing data from 27 LAC countries. In total, 17 DBM combinations at the household and individual level were identified, yielding 360 prevalence estimates. DBM prevalence ranged from 0% to 24% in the LAC region; however, the magnitude of DBM strictly depended on the DBM combination. The highest prevalence was observed for the combination of a child with anemia and an adult with overweight (24%), while the most frequently reported combination was a child with stunting and a woman with overweight (CS-WO), 9%. 
Chapter 3 describes the prevalence, temporal trends, and socio-demographic factors associated with household- and individual-level DBM in Guatemala. This study analyzed four rounds of the Demographic and Health Surveys conducted between 1998 and 2015, comprising a total of 39,749 households. The prevalence of household- and individual-level DBM remained stable over time, ranging from 24% to 26%. The most prevalent DBM combination was SC-WO, affecting 18–19% of households, with no significant changes over time. Socio-demographic factors associated with lower odds of DBM included rural residence, female-headed households, higher wealth, and women’s secondary education. In contrast, higher odds were observed in households with electricity, women over 25 years of age, an Indigenous background, and having more than two children.
Chapter 4 analyzes data from the Guatemalan Epidemiological Health and Nutrition Surveillance System collected in 2013, 2015, 2016, 2017/18, and 2018/19 to identify socio-demographic factors uniquely associated with households experiencing DBM (SC-WO), as well as those shared with households affected by single forms of malnutrition. Among 3,622 households surveyed, one-fifth presented DBM. Unique factors associated with DBM households included a middle level of household assets and women without health insurance. Shared factors with households where a woman had overweight/obesity were residence in the Central region, women aged >25 years, and children >18 months. Shared factors with households having a child with stunting included women’s primary education and Indigenous ethnicity. Across DBM households and those with either single form of malnutrition, shared factors included no formal education, parity greater than three, and children aged 18–36 months.
Chapter 5 outlines an analysis to examine the association between maternal pre-pregnancy anthropometric status and offspring’s linear growth over the first 24 months of life. This study uses data from the Women First Trial, a randomized controlled study on maternal nutrition supplementation conducted in four LMICs, including Guatemala. The analysis included 2,228 mother–child pairs. Pre-pregnancy, 17% of mothers presented underweight, 21% short stature, 5% overweight, 6% underweight and short stature, and 14% short stature and overweight. Two distinct child growth trajectories were identified: no/mild growth faltering (n=1,238) and severe growth faltering (n=990). Compared with children of mothers with a pre-pregnancy normal anthropometric status, those born to mothers with underweight, short-stature, underweight and short stature, and short stature and overweight/obesity had higher risks of severe growth faltering.
Chapter 6 presents the development process, final version, and dissemination plan of an issue brief produced as part of this doctoral research to raise awareness of DBM in Guatemala among key public health stakeholders. The brief was informed by a round table discussion with Guatemalan public health nutrition experts and by the scientific evidence generated through this thesis. It summarizes the background and implications of DBM, outlines the current national situation based on thesis findings, including prioritized DDAs suggested by national experts, and offers short- and long-term policy recommendations. Dissemination efforts include distribution of printed copies to relevant stakeholders, online publication in open-access repositories, and promotion via social media.
Chapter 7 provides a general discussion organized by research questions. Each section presents an in-depth discussion of the findings and their interpretation, examines their relevance and implications, and compares them with existing evidence. A critical outlook section is then provided, followed by recommendations to guide future international and Guatemalan scientific research and public health policies in Guatemala, and an overall conclusion. 

Recommendations
For scientific research, both international and in Guatemala:
-    Develop standardized research guidance for operationalizing the DBM definition.
-    Expand research on DBM to include environmental and food systems drivers.
-    Prioritize life-course and longitudinal designs, understudied populations, and diverse malnutrition indicators in DBM research.
-    Integrate behavioral research, using gender-sensitive approaches and collective accountability frameworks, to co-develop context-specific DDAs.
-    Strengthen implementation research to evaluate the effectiveness of context-specific DDAs through human-centered designs and mixed methods.
For public health policy in Guatemala:
-    Promote a unified understanding of malnutrition and DBM across sectors.
-    Target vulnerable populations with tailored and equity-focused strategies. 
-    Update and contextualize nutrition education materials, strengthen delivery capacity, and integrate into school curricula.
-    Strengthen systems for continued monitoring, evaluation, and implementation research.
-    Reinforce malnutrition-focused programs and policies by integrating environmental and food system approaches.

Conclusion
This doctoral thesis generated original evidence on the high burden and complexity of DBM in LAC, identifying CS-WO as the most common DBM in the region. In Guatemala, about one in four households experienced DBM, with one in five affected by CS-WO in 2019. Factors such as poverty, low education, Indigenous background, and the co-existence of maternal pre-pregnancy short stature and overweight emerged as major contributors to this persistent burden. Women of reproductive age with short stature and their children remain an underserved group that should be prioritized to tackle DBM. Although Guatemala has achieved progress in reducing undernutrition, the ongoing fragmentation of initiatives addressing undernutrition and overnutrition limits the overall effectiveness of national strategies. A coordinated, multi-sectoral, life-course approach aligned with prioritized DDAs is essential to sustainably reduce DBM and improve population health and well-being.