New Delhi: People living with obesity are much more likely to fall seriously ill or die from infectious diseases, a new study published in The Lancet has found. The study published Tuesday said that obesity may have been linked to about one in ten infection-related deaths across the world in 2023.
Analysing data from over 540,000 adults in Finland and the UK, the study found that people with obesity were 70 percent more likely to be hospitalised, or die due to an infectious disease compared to people with a healthy body weight.Those with very severe obesity faced three times the risk of getting down with an infection, the study said.
Obesity is a medical condition where a person has too much body fat. It is commonly measured using body mass index (BMI), which is based on height and weight. A person with a BMI of 30 kg/m² or more is classified as obese.
Nearly a quarter of adults in India are overweight or obese, affecting 24 percent of women and 23 percent of men, according to the National Family Health Survey (NFHS)-5 (2019–21).
The Lancet study tried to fill an evidence gap. “During the COVID-19 pandemic, people with obesity had a higher risk of being hospitalised or dying with the SARS-CoV-2 infection, however there was a lack of evidence on if this link exists for infectious diseases in general,” the study pointed out.
To address this gap, researchers analysed data from more than 67,000 adults across two studies in Finland and over 470,000 adults from the UK Biobank—a large health database—to examine the link between obesity and severe infectious diseases.
During the study, BMI of participants was recorded at the start, and they were followed for 13 to 14 years on average. The researchers tracked hospital admissions and deaths caused by infectious diseases during the follow-up period.
They found that obesity raised the risk of severe illness or death from most infections. These included flu, COVID-19, pneumonia, gastroenteritis, urinary tract infections and lower respiratory tract infections.
However, obesity did not appear to increase the risk of severe HIV or tuberculosis, the authors noted.
The risk of infection went up as body weight increased. For instance, in the UK Biobank group, people with a healthy BMI had a 1.1 percent chance each year of having a severe infection. Whereas for people with obesity, this risk increased to 1.8 percent per year.
To study the worldwide estimates, the researchers then used global data from the Global Burden of Diseases (GBD) Study. They found that obesity may have been linked to around 0.6 million out of 5.4 million infectious disease deaths globally in 2023, i.e., about 10.8 percent, or one in ten deaths.
“Our findings suggest that people living with obesity are significantly more likely to become severely ill or to die from a wide range of infectious diseases. As obesity rates are expected to rise globally, so will the number of deaths and hospitalisations from infectious diseases linked to obesity,” Dr Solja Nyberg of the University of Helsinki in Finland said.
The impact varied with several countries. In the US, obesity was linked to about one in four infection-related deaths. In the UK, it was linked to around one in six. In Vietnam, the share was much lower, at about 1 percent.
The authors also said the findings should be interpreted carefully as the analysis was based on observational data, meaning it cannot establish a cause-and-effect relationship.
They also cautioned that participants from the Finnish cohorts and the UK Biobank do not reflect the general population, so the findings may not be fully generalisable.
Dr Sara Ahmadi-Abhari of Imperial College London, who led the GBD analyses, said that while global estimates help illustrate the scale of the problem, they must be interpreted carefully, as data on obesity and infection-related deaths in the GBD have inherent limitations.
UNICEF’s Child Nutrition Global Report 2025 states that obesity has, for the first time, overtaken underweight as the most prevalent form of malnutrition among school-aged children and adolescents worldwide. Currently, about one in ten children globally—around 188 million—are living with obesity.
Commenting on the findings of the study published in The Lancet, Dr Anoop Misra, chairperson, Fortis C-DOC Hospital for Diabetes and Allied Sciences in New Delhi, said the results are particularly relevant for India, where infection burden remains high.
“Indians develop diabetes and metabolic dysfunction at much lower levels of obesity, which further impairs immunity. When obesity, diabetes, air pollution, overcrowding, and poor hygiene coexist—as they do in many parts of India—the infection risk is likely to be substantially higher than what Western cohorts estimate,” he told The Print.
Obesity, according to Dr Atul Kakar, chairperson, Internal Medicine, Sir Ganga Ram Hospital, is linked to low-grade inflammation and impaired immunity across the gut, skin and respiratory system, which increases infection risk.
(Edited by Tony Rai)