People with obesity not only face an increased risk of diabetes and . A study reveals that obesity drastically increases vulnerability to serious infections: people who suffer from it are 70% more likely to be hospitalized or die from infectious diseases such as flu, covid, pneumonia or urinary infections. In cases of severe obesity, which the study reveals as over 40, the risk triples.
The study followed almost 68,000 Finnish adults and 480,000 British adults for 13 years, and analyzed their risk of suffering from 925 different types of serious infections, that is, those that require hospitalization or cause death. The results show a clear relationship: the higher the BMI, the greater the risk. According to their data, approximately one in ten deaths from infections in the world – 600,000 out of 5.4 million in 2023 – could be attributed to obesity. During the Covid pandemic, this proportion shot up to 15%.
“Our findings suggest that people living with obesity are significantly more likely to become seriously ill or die from a wide spectrum of infectious diseases,” explains Solja Nyberg, from the University of Helsinki and lead author of the study. Diego Bellido, president of the Spanish Society for the Study of Obesity (SEEDO) and who has not participated in this study, explains: “Ignoring obesity in infection prevention strategies means underestimating up to 10% or 15% of the global burden of infectious mortality.”
Country-by-country data from the research reveal significant differences in the impact of obesity on infectious deaths. In Spain, it would be linked to 5,300 of the 24,800 deaths from infections registered in 2023, which represents 21.2% of the total. It is more than double the world average (10.8%). Spain is thus among the European countries with the highest proportion of infectious deaths attributable to obesity, above Germany (14.7%) or the United Kingdom (17.4%), although below the United States, where obesity is behind one in four deaths due to infections (25.7%), according to the study.
There are also differences related to the weight of the patients. Although it is used as a measure to assess obesity, it has been used in this study. The conclusions indicate that people with class I obesity (BMI 30-34.9) have 1.5 times more risk than those who maintain a healthy weight. In class II obesity (BMI 35-39.9), the risk doubles. And in class III or morbid obesity (BMI ≥40), the risk is three times higher.
The pattern is maintained for almost all types of infections analyzed – bacterial, viral, parasitic and fungal – with two notable exceptions: HIV and tuberculosis, where the inverse association, probably because both diseases cause pronounced weight loss. And among specific infections, those of the skin and soft tissues are those that showed the highest risk (2.8 times higher), followed by covid, gastrointestinal and urinary infections.
¿Irreversible?
An interesting thing about this study is that the researchers also examined whether losing weight reduces that risk of getting more infections. The data suggests yes, but in a modest way: people who lost weight from obesity to what is called normal weight (with a BMI of between 18.5 and 24.9 in adults, according to the WHO) reduced their risk to 0.8 times that of those who remained obese, although they did not reach the risk levels of those who always maintained a healthy weight. This suggests that the immunological and metabolic damage of obesity could be partially irreversible, although the researchers note that it could simply reflect the limited follow-up time.
Mika Kivimäki, from University College London, who led the study, explains: “This finding that obesity is a risk factor for a broad spectrum of infectious diseases suggests that broad biological mechanisms are involved. It is plausible that obesity weakens the immune system’s ability to defend itself against infectious bacteria, viruses, parasites or fungi, resulting in more severe diseases.”
The authors believe that to reduce the risk of serious infections, as well as other health problems linked to obesity, there is an urgent need for policies that help people stay healthy and support weight loss, such as access to healthy foods and increasing opportunities for physical activity. They also add that, in addition, for people with obesity, it is especially important to keep recommended vaccines up to date.
