[Comment] Undernutrition and tuberculosis: time to recalibrate the global response

Undernutrition and tuberculosis: time to recalibrate the global response Affiliations & Notes aNational Tuberculosis Institute, Bengaluru, Karnataka, India bNational Disease Modelling Consortium, Indian Institute of Technology, Bombay, Mumbai, Maharashtra, India Article Info Publication History: Published May 11, 2026 DOI: 10.1016/S2214-109X(26)00091-4 External LinkAlso available on ScienceDirect External Link Copyright: © 2026 The Author(s). Published by Elsevier Ltd. Linked Articles - Global, regional, and national estimates of tuberculosis incidence averted by eliminating undernutrition in adults: a modelling studyThe Lancet Global HealthMay 11, 2026 Download started OkThe relationship between undernutrition and tuberculosis is one of the oldest observations in infectious disease epidemiology, yet its precise quantification has remained elusive. In The Lancet Global Health, Matthew J Saunders and colleagues present the findings of a modelling study estimating that eliminating all undernutrition (BMI <18·5 kg/m2) among adults globally could avert 23·7% (95% uncertainty interval 20·9–26·5) of adult tuberculosis incidence worldwide.1 This estimate is approximately two and a half times higher than the current WHO population attributable fraction of 8·9%,2 a difference that warrants attention. The major methodological contribution of this study lies in treating BMI as a continuous concept rather than WHO's approach of classifying individuals as either having undernutrition or not, applying a single relative risk estimate. By fitting gamma distributions to country, sex, and age-specific BMI data and applying a bilinear log–risk function from a recent dose–response meta-analysis of more than 26 million individuals,3 the authors capture heterogeneity in the BMI continuum that the binary framework misses. The disaggregation by WHO region, sex, and 5-year age groups enhances the policy utility of the study, showing that populations in the WHO African, South-East Asia, and Eastern Mediterranean regions, along with females, adolescents, and older adults, stand to benefit the most from nutritional interventions. The present study provides a timely evidence base for expanding nutritional interventions when the WHO End TB strategy targets are still far away, with only an 8·3% decline in incidence between 2015 and 2023.2 The current geopolitical scenario and its impact on the development funding infrastructures, along with rising food insecurity driven by conflict, climate change, and pandemic aftershocks is expected to worsen undernutrition, more so in settings where the tuberculosis burden is high.4 Certain important questions remain unaddressed and have been rightly acknowledged by the authors as the study's limitations. First, the causal interpretation of the association between BMI and tuberculosis deserves a more granular look. Reverse causality and confounding by shared determinants and the magnitude of this bias remain unquantified. Analyses leveraging natural experiments could help understand and quantify these effects, especially in settings where the determinants could be of significance or expected to be of significance (eg, conflict-affected settings). Second, applying a single global risk function across all populations, as done by authors, might obscure important effect modification or interaction by other determinants (eg, HIV and tuberculosis co-infection, the diabetes burden, and so on). Finally, BMI is considered to be a one-way path for population transition (ie, once people develop undernutrition they do not naturally return to a normal nutritional status unless they receive nutritional interventions). The natural transition of the population between different BMI levels along the life-cycle continuum needs systematic exploration. The sensitivity analyses done by Saunders and colleagues,1 applying four counterfactual distributions, ensure the robustness of their findings. Even the most conservative scenario yielded reductions exceeding 15% of global adult tuberculosis incidence. This strengthens the policy use case, although all scenarios represent the theoretical minimum risk rather than achievable intervention outcomes. The gap between what is theoretically attributable and what is practically avertable remains the critical unknown. The authors have made the findings clearer and more visible for programme managers and policy makers in addition to the academic community. Prioritising adults with moderate to severe undernutrition (BMI <17 kg/m2), who constitute 5% of the global adult population, an achievable target, could avert 15% of adult tuberculosis incidence, while targeting all adults with undernutrition, who constitute 10% of the global adult population, could avert 24% of adult tuberculosis incidence. However, in order to achieve this goal, countries will need to simultaneously work to address the existing burden of undernutrition as well as prevent the population from falling into undernutrition. In this context, nutritional interventions are to be understood as fundamental components, with benefits extending to reductions in overall child mortality, better maternal health, better mental health, and improved economic productivity. Further research priorities could include basic scientific exploration of the natural life cycle of the population in the BMI continuum; estimating the interactions of undernutrition with other determinants of tuberculosis, including its biological pathways; determining optimal intervention designs, especially those that are population-level strategies or at the subgroup level (eg, the older population) focusing beyond tuberculosis-affected households; and establishing the cost-effectiveness of such interventions across varied settings. To conclude, with the converging crises in food security, the climate, and development financing globally, more so in low-income and lower-income and middle-income settings, the case for investing to prevent and manage undernutrition as a tuberculosis prevention measure has never been stronger. Competing Interests We declare no competing interests. References 1. Saunders, MJ ∙ McQuaid, CF ∙ Sinha, P ∙ et al. Global, regional, and national estimates of tuberculosis incidence averted by eliminating undernutrition in adults: a modelling study Lancet Glob Health. 2026; published online May 11. https://doi.org/10.1016/S2214-109X(26)00065-3 2. WHO Global tuberculosis report 2024 3. Saunders, MJ ∙ Cegielski, JP ∙ Clark, RA ∙ et al. Body mass index and tuberculosis risk: an updated systematic literature review and dose–response meta-analysis Int J Epidemiol. 2025; 54, dyaf154 4. Hendriks, SL ∙ Montgomery, H ∙ Benton, T ∙ et al. Global environmental climate change, covid-19, and conflict threaten food security and nutrition BMJ. 2022; 378, e071534