NEW evidence has revealed that obesity substantially increases the risk of severe infections and infection-related deaths across bacterial, viral, parasitic, and fungal diseases. The multicohort study, involving more than half a million participants from Finland and the UK, suggests that around one in ten global infection deaths may now be attributable to excess body weight.
Obesity’s Hidden Toll on Infection Risk
Obesity, defined as a BMI of 30 kg/m² or higher, is already known to raise risks for cardiovascular disease, diabetes, and certain cancers. This large-scale analysis extends its impact to infectious disease, highlighting the condition as a modifiable but underappreciated risk factor for immune vulnerability and poor infection outcomes.
Large Studies Confirm Widespread Association
Researchers combined data from two Finnish cohort studies and the UK Biobank, following participants for infection-related hospitalisations and deaths. Across both populations, totalling almost 550,000 adults, obesity was consistently associated with increased infection risk, regardless of age, sex, or underlying health.
Adults with class III obesity (BMI ≥ 40) were roughly three times more likely to be hospitalised or die from infections than those of healthy weight. Even moderate obesity carried a 70% higher risk of severe or fatal infection. This pattern held across diverse pathogens, from common bacterial and viral infections to rarer parasitic and fungal conditions. The link persisted when obesity was assessed using other measures such as waist circumference or waist-to-height ratio.
Global Burden Rising After the Pandemic
Applying these results to international obesity prevalence data, researchers estimated that about 8.6% of infection-related deaths were attributable to obesity before the COVID‑19 pandemic in 2018, rising to 15% during 2021 and settling at 10.8% in 2023. These figures suggest that obesity’s contribution to fatal infections intensified in the pandemic years and remains substantial today.
The findings highlight the need for integrated prevention strategies that tackle obesity not only as a metabolic or cardiovascular risk but also as a determinant of infection susceptibility, recovery, and survival. For clinicians, this expands the rationale for weight management interventions as part of comprehensive infection‑risk reduction.
Reference
Nyberg ST et al. Adult obesity and risk of severe infections: a multicohort study with global burden estimates. Lancet. 2026; DOI:10.1016/S0140-6736(25)02474-2.
