People who are very overweight have a drastically increased risk of suffering severe illness or even death if infected. This is the conclusion reached by a new study.
02/10/2026, 03:1102/10/2026, 03:11
This comes from an analysis of health data from more than 540,000 patients in the United Kingdom and Finland. While being slightly overweight only increases the risk slightly, it is around three times as high for people with category 3 obesity as for people of normal weight. The study by a group led by Mika Kivimäki from University College London and Solja Nyberg from the University of Helsinki was published in the journal “The Lancet”.
One of the biggest health problems facing humanity: obesity. (symbol image)Image: Shutterstock
The starting point for the study were observations a few years ago: “Studies during the Covid-19 pandemic showed that overweight people had a higher risk of a severe course of a Sars-Cov-2 infection, which was reflected in increased hospital stays and higher mortality,” writes the team. However, it was not clear whether this also applied to other infectious diseases.
The team led by Kivimäki and Nyberg therefore used health data from two Finnish databases and the British “UK Biobank” to investigate the connection between overweight and obesity and a severe course of infections such as hospitalization or even death.
The analysis showed that being slightly overweight increased the risk of serious or fatal infections by 10 percent in Finland and by 13 percent in the United Kingdom (Great Britain and Northern Ireland).
For category 1 obesity (body mass index 30 to 34.9), the risk was already 47 percent higher in Finland and 53 percent higher in the United Kingdom than for people of normal weight. Category 3 obesity (body mass index 40 or above) resulted in a 2.69-fold increased risk in Finland and a 3.07-fold increase in the United Kingdom. Other factors such as gender, age or socioeconomic status had little influence on this result.
Favorable conditions for germs
“It is plausible that obesity weakens the ability of the immune system to defend itself against infectious bacteria, viruses, parasites or fungi, which can lead to more severe disease progression,” Kivimäki is quoted as saying in a statement by The Lancet.
The reasons could be factors associated with obesity, such as a nutrient-rich environment that promotes the survival of microorganisms, as well as insulin resistance, hyperglycemia and chronic low-grade inflammation. However, the study authors also write that the data shows the connection between obesity and the risk of infection, but not the exact reasons for it.
The researchers transferred the knowledge gained to data from the “Global Burden of Disease” study and were thus able to calculate the risk of severe infection for regions of the world and for individual countries. In Germany, for example, 4,700 of 31,900 deaths after infections in 2023 were linked to obesity; that was 14.7 percent of these deaths. This puts the country below the values of the USA (25.7 percent), Spain (21.2 percent), Great Britain (17.4 percent), but significantly above those of China (9.0 percent) and India (3.8 percent).
Rising obesity rates expected
The study authors warn that the situation could worsen in the coming years. “As obesity rates are expected to rise worldwide, the number of deaths and hospitalizations due to obesity-related infectious diseases will also increase,” says Nyberg.
In order to reduce the risk of serious infections and other health problems associated with obesity, there is an urgent need for measures that help people stay healthy and reduce weight, emphasizes the researcher. (sda/dpa/con)