People with obesity more likely to be hospitalised or die from infections

A major Lancet study finds adults with obesity are far more likely to be hospitalised or die from infections, linking nearly one in 10 infection deaths worldwide to excess weight

From flu to Covid-19, obesity significantly raises the risk of hospitalisation and death from infections, a large international study published in The Lancet has found. The findings suggest that body weight may play a decisive role in how severely infections affect individuals, beyond its well-known links to heart disease and diabetes. 

Titled Adult obesity and risk of severe infections: a multicohort study with global burden estimates, the research analysed health data from more than half a million adults in Finland and the United Kingdom. It found that adults living with obesity were 70 per cent more likely to be hospitalised or die due to infections. Globally, around one in 10 infection-related deaths may now be linked to obesity.

 

What the study found

While obesity has long been associated with worse outcomes during the Covid-19 pandemic, it was unclear whether the risk extended to infections more broadly. To examine this, researchers followed participants for more than a decade, linking baseline body mass index (BMI) to subsequent hospitalisations or deaths from 925 different infectious diseases. 

Compared with adults in the healthy BMI range of 18.5 to 24.9, those with obesity, defined as a BMI of 30 or higher, had a 70 per cent higher risk of severe infection outcomes. Among people with severe obesity, with a BMI of 40 or above, the risk was nearly three times higher. 

The study highlights that the elevated risk appeared across bacterial, viral, parasitic and fungal infections, suggesting a broad biological effect rather than a disease-specific one.

Which infections show the strongest links

The strongest links were seen with common but potentially dangerous infections, including:

• Skin and soft tissue infections, such as cellulitis
• Respiratory infections, including influenza and pneumonia
• Covid-19, where obesity more than doubled the risk of severe outcomes
• Urinary tract and gastrointestinal infections

ALSO READ: Obesity close to home: 3 in 4 Indians know someone living with obesity 

Why obesity worsens infection outcomes

According to the researchers, excess fat tissue is associated with chronic low-grade inflammation, impaired immune cell function, insulin resistance and poorer lung mechanics. 

Together, these changes can weaken the immune system’s ability to fight off bacteria and viruses, allowing infections to become more severe once they take hold.

How big is the global impact of obesity-linked infections?

Using global disease data, researchers estimated that obesity may already be contributing to around 600,000 infection-related deaths each year, out of roughly 5.4 million worldwide. 

The burden varies by region. In high-income countries like the UK and the US, obesity was linked to one in six to one in four infection deaths. In contrast, countries with lower obesity prevalence, such as Vietnam, saw far smaller proportions. 

During the Covid-19 pandemic, the share of infection deaths attributable to obesity rose sharply to about 15 per cent worldwide, before easing to around 11 per cent in the post-pandemic period. 

Can weight loss reduce the risk?

The study suggests that reducing body weight can lower the risk of severe infections. Participants who moved from the obesity category to a lower BMI group saw a decline in infection risk, although not to the same level as those who had always remained within a healthy weight range. 

Emerging evidence from trials of GLP-1 weight-loss drugs has also shown fewer serious infections among people who lose weight. 

The study authors stress the importance of preventive strategies, including access to healthy food, opportunities for physical activity and supportive weight-loss care. In the meantime, staying up to date with vaccinations is especially important for people living with obesity, the researchers say.