Obesity causes one in ten deaths from infections worldwide

The work, published in The Lancet, found that obese people were 70% more likely to be hospitalized or die due to infection than people of normal weight. Moreover, the risk increases as the body mass index (BMI) increases: with a BMI of 40 and above, it is three times higher than that of people with a healthy weight. The researchers analyzed data from more than 540,000 participants in long-term cohort studies in the UK (UK Biobank) and Finland. Participants’ BMI was recorded at baseline and they were followed for an average of 13–14 years. The association between obesity and severe infections persisted regardless of which measure of obesity was used—BMI, waist circumference, or waist-to-height ratio.

The analysis included data on 925 bacterial, viral, parasitic and fungal infections, as well as a detailed look at the ten most common diseases. For most of them – including influenza, COVID-19, pneumonia, gastroenteritis, urinary tract and lower respiratory tract infections – obese people were more likely to be hospitalized or die. The exceptions were HIV and tuberculosis, where no such association was found. Importantly, the observed association was not explained by comorbidities such as diabetes, metabolic syndrome or cardiovascular disease, nor was it dependent on physical activity levels. Scientists suggest that the effects of obesity on the immune system play a key role: chronic inflammation, metabolic disorders and dysregulation of the immune response. However, obese people who managed to lose weight had about 20% lower risk of severe infections than those who remained at the same weight.

Using data from the Global Burden of Disease (GBD) project, researchers assessed the possible contribution of obesity to infection mortality worldwide. According to their calculations, of the 5.4 million deaths from infectious diseases in 2023, about 600 thousand (10.8%) could be associated with obesity. In the UK, the proportion of such deaths is estimated at 17%, and in the US at 26%, although the authors stress that these estimates should be interpreted cautiously due to data limitations. The authors note that as the prevalence of obesity increases worldwide, the number of severe infections will also increase. They emphasize the importance of weight loss measures, access to healthy diets, physical activity and up-to-date vaccinations for people with obesity.