People with a certain BMI are more prone to deadly infections, study reveals

The researchers analyzed medical data from nearly 550,000 adults in Finland and the U.K. over a 14-year period, finding that obese patients were 70% more likely to be hospitalized with or die from an infection. 

The Finnish patients averaged 42 years of age, while the average age of U.K. patients was 57. Obesity was defined by a BMI (body mass index) of 30 or above.

Based on risk calculations, the researchers estimated that obesity played a role in about 9% of infection-related deaths in 2018, about 15% in 2021 and about 11% in 2023.

The association was even seen in obese people who did not have diabetes, heart disease or metabolic syndrome. The amount of physical activity also did not appear to affect the link.

Nearly all types of infection were linked to higher risk of obesity in terms of poor outcomes, the researchers found.

The conditions that were most strongly associated with obesity were skin and soft-tissue infections.

Professor Kivimaki added, "Our findings suggest that obesity weakens the body's defenses against infections, resulting in more serious diseases. People may not get infected more easily, but recovery from infection is clearly harder."

Based on the findings, the researchers concluded that up to 11% of infection-related deaths globally could be prevented by addressing obesity.

"As obesity rates are expected to rise globally, so will the number of deaths and hospitalisations from infectious diseases linked to obesity," first author Dr. Solja Nyberg at the University of Helsinki commented in the press release.

She also emphasized the importance of obese people staying up to date with their vaccinations.

The study did have some limitations, primarily that it only shows a strong link between obesity and infection severity, but doesn't prove causation, the researchers noted.

There is also some debate surrounding the reliability of BMI as a definition of obesity.

The study is limited to adults from Finland and the UK Biobank, so it may not apply to other populations.

The study was funded by Wellcome, Medical Research Council and Research Council of Finland.