People living with obesity face a significantly increased risk of hospitalization or death from infectious diseases, according to new research published in in The Lancet. The study, involving data from over 500,000 individuals, reveals that obese individuals are 70% more likely to be hospitalized or die from infection compared to those with a healthy weight.
The findings highlight a concerning link between excess weight and susceptibility to a wide range of infections, including influenza, pneumonia, urinary tract infections, and even COVID-19. Researchers estimate that obesity may already be a contributing factor in approximately 11% – or around 600,000 – of the 5.4 million annual deaths from infectious diseases globally.
A U-Shaped Risk Curve
This isn’t a simple linear relationship. Previous research, including a study published in 2020, demonstrates a U-shaped association between body mass index (BMI) and hospitalization risk for infections. That earlier work showed that individuals who are underweight actually face the greatest risk of hospitalization, followed closely by those with obesity. This suggests that both extremes of the weight spectrum compromise the body’s ability to fight off infection.
How Obesity Impacts Immune Function
The mechanisms underlying this increased vulnerability are complex, but experts believe obesity weakens the immune system. “It is plausible that obesity weakens the immune system’s ability to defend against the infectious bacteria, viruses, parasites or fungi, therefore resulting in more serious diseases,” explains Professor Mika Kivimäki of University College London, lead author of the Lancet study.
Obesity is often associated with chronic, low-grade inflammation throughout the body. This persistent inflammatory state can impair both the innate and adaptive immune responses – the body’s first and second lines of defense against pathogens. Obesity can affect physical aspects of immune function, potentially altering skin barrier function and wound healing, increasing the risk of cutaneous infections.
Global Variations in Risk
The study also revealed geographical differences in the proportion of infection-related deaths linked to obesity. In the United Kingdom, approximately one in six infectious disease deaths were associated with obesity, while in the United States, that figure rose to one in four. Vietnam showed the lowest proportion, with obesity linked to just 1.2% of infection deaths. These variations likely reflect differences in obesity prevalence and healthcare access across these countries.
The Role of GLP-1 Medications
Interestingly, the researchers note that emerging evidence from trials of GLP-1 receptor agonist medications – a newer class of drugs used for weight loss – suggests that reducing obesity may also lower the risk of severe infections. This observation supports the idea that addressing obesity can have broad health benefits, extending beyond metabolic control to include improved immune function.
Study Details and Limitations
The research involved analyzing data from two large cohorts: 67,000 adults in Finland and 470,000 adults participating in the UK Biobank study. Participants had their BMI assessed and were followed for an average of 13 to 14 years. The average age of participants at the study’s outset was 42 in the Finnish group and 57 in the UK cohort.
It’s important to acknowledge the study’s limitations. As an observational study, it cannot definitively prove a causal relationship between obesity and increased infection risk. The researchers relied on existing data and could not control for all potential confounding factors. “Estimates of the global impact give a sense of how large the problem may be, but they should be interpreted with caution,” cautions Dr. Sara Ahmadi-Abhari of Imperial College London, a co-author of the study.
Public Health Implications and Recommendations
Despite these limitations, the findings underscore the urgent need for public health strategies to address the growing obesity epidemic. “As obesity rates are expected to rise globally, so will the number of deaths and hospitalisations from infectious diseases linked to obesity,” warns Dr. Solja Nyberg of the University of Helsinki, the study’s first author.
She emphasizes the importance of policies that promote healthy lifestyles, including access to affordable, nutritious food and opportunities for regular physical activity. In the meantime, she adds, “it was especially important” for individuals living with obesity to stay up-to-date with recommended vaccinations, as they are particularly vulnerable to severe complications from infectious diseases.
The research reinforces the understanding that obesity is not simply a cosmetic concern, but a significant public health issue with far-reaching consequences, including increased susceptibility to life-threatening infections.
