Study Links Obesity to Higher Risk of Severe Infections and Death

Obesity may contribute to more than one in ten infection-related deaths worldwide, according to an extensive new study published in The Lancet. Researchers analyzing medical data from nearly 550,000 adults in Finland and the United Kingdom found that obese patients faced a 70% higher risk of hospitalization or death from infections compared to those maintaining a healthy weight.

The 14-year study tracked patients with an average age of 42 years in Finland and 57 years in the UK. Those classified with “class 3 obesity” – defined as having a body mass index (BMI) of 40 or higher – faced particularly dire outcomes, being three times more likely to require hospitalization or die from infections than individuals with a healthy BMI between 18.5 and 24.9.

“Obesity is well-known as a risk factor for metabolic syndrome, diabetes, cardiovascular disease and many other chronic conditions,” said Professor Mika Kivimaki, the study’s lead author from University College London’s Faculty of Brain Sciences. “Here, we have found robust evidence that obesity is also linked to worse outcomes from infectious diseases, as becoming very ill from an infection is markedly more common among people with obesity.”

Based on risk calculations, the researchers estimated obesity’s role in infection-related mortality at approximately 9% in 2018, rising to 15% in 2021, and settling at about 11% in 2023. Notably, the research examined 925 different infectious diseases, including influenza, COVID-19, pneumonia, gastroenteritis, urinary tract infections, and lower respiratory tract infections.

The connection between obesity and poor infection outcomes remained consistent even in patients without other health complications like diabetes, heart disease, or metabolic syndrome. Physical activity levels also did not appear to mitigate the risk. Skin and soft-tissue infections showed the strongest association with obesity-related complications.

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

The research offers some hope, however. Patients who were initially obese but subsequently lost weight reduced their risk of severe infections by approximately 20%. This finding underscores the potential benefits of weight management in improving infection resilience.

Dr. Solja Nyberg from the University of Helsinki, the study’s first author, warned about the implications of rising global obesity rates: “As obesity rates are expected to rise globally, so will the number of deaths and hospitalizations from infectious diseases linked to obesity.”

The researchers emphasized the urgent need for comprehensive public health strategies that help people maintain healthy weights. “There is an urgent need for policies that help people stay healthy and support weight loss, such as access to affordable healthy food and opportunities for physical activity,” Dr. Nyberg stated. She also stressed the importance of vaccination adherence for obese individuals.

The study, funded by Wellcome, the Medical Research Council, and the Research Council of Finland, does have limitations. While establishing a strong correlation between obesity and infection severity, it does not conclusively prove causation. Additionally, the research relied on BMI as the definition of obesity, a metric some experts consider imperfect. The findings are also based on adult populations specifically from Finland and the UK Biobank, potentially limiting their applicability to other demographic groups.

Nevertheless, the research represents one of the most comprehensive examinations to date of obesity’s impact on infectious disease outcomes, suggesting that addressing obesity could potentially prevent up to 11% of infection-related deaths globally.