London: People living with obesity face a significantly higher risk of severe illness and death from infectious diseases, with new research suggesting that obesity may be linked to nearly one in ten infection-related deaths worldwide.
The findings come from a large international study published in The Lancet, based on data from more than 540,000 adults followed over more than a decade. It found that individuals with obesity were about 70% more likely to be hospitalised or die due to an infectious disease compared with people of healthy weight.
According to the findings, those with the most severe obesity were at even greater risk, facing nearly three times the likelihood of severe outcomes. When researchers applied these risk estimates to global mortality data, they found that obesity may have contributed to about 0.6 million of the 5.4 million infectious disease deaths recorded globally in 2023.
Researchers analysed long-term data from two large Finnish cohorts and the UK Biobank, tracking participants for an average of 13 to 14 years. Body mass index (BMI) was recorded at the start of the studies, and participants were monitored for hospitalisation or death related to infectious diseases. People with a BMI of 30 or higher consistently showed higher risks across most infections studied.
According to the analysis, obesity increased the risk of severe illness or death from infections such as influenza, COVID-19, pneumonia, gastroenteritis, urinary tract infections and lower respiratory tract infections. However, no clear increase in risk was observed for HIV or tuberculosis. The findings suggest that excess body weight may broadly impair the body’s ability to respond to infections.
Study author Dr Solja Nyberg of the University of Helsinki said the results indicate a growing global challenge. She noted that as obesity rates continue to rise worldwide, the number of severe infections linked to obesity is also likely to increase in the coming decades. She stressed the importance of public health policies that promote healthy diets, physical activity and access to preventive healthcare, including vaccinations.
The study also highlighted wide differences between countries. In high-income nations, obesity appeared to play a much larger role in infection-related deaths. In 2023, about one in four infectious disease deaths in the United States and nearly one in six in the United Kingdom were linked to obesity. In contrast, the proportion was much lower in countries such as Vietnam, where obesity rates remain comparatively low.
Professor Mika Kivimäki of University College London, who led the research, said the findings point to underlying biological mechanisms. He suggested that obesity may weaken immune responses, making it harder for the body to fight off bacteria, viruses and other pathogens. He added that emerging evidence from weight-loss drug trials indicates that reducing obesity could also lower the risk of severe infections, though further research is needed.
Experts said the findings reinforce the need to treat obesity as a serious health condition. Professor Volkan Demirhan Yumuk, president of the European Association for the Study of Obesity, said, “Obesity increases the risk of severe illness and death from infectious diseases, while also driving other major non-communicable diseases including cardiovascular diseases, diabetes and some cancers. This new evidence further highlights the urgent need for health systems to prioritise obesity as a serious non-communicable disease in policy and planning.”
The authors cautioned that their global estimates should be interpreted carefully, as the study was observational and relied on existing health data that may be incomplete in some regions. The Finland cohorts and UK Biobank are not representative of the general population so generalisability should be treated cautiously, they said Still, they added, the results underline the urgent need for coordinated action to address obesity as a growing driver of infectious disease burden worldwide.
Dr Sara Ahmadi-Abhari, Imperial College London (UK), who conducted the GBD analyses, says: “Estimates of the global impact give a sense of how large the problem may be, but they should be interpreted with caution. Data on infection-related deaths and obesity in the GBD are not always accurate, particularly in low-resource countries.”
