OBESITY LINKED TO RISK OF SEVERE AND FATAL INFECTIONS

Obesity was tied to a higher risk for infection-related hospitalizations and death, according to a prospective multicohort study.

Compared with people with healthy weight, those with class III obesity (body mass index [BMI] ≥40) in two Finnish cohorts and an independent population from the U.K. Biobank had higher risks of:

• Infection-related hospital admissions: HR 2.75 (95% CI 2.24-3.37) and HR 3.07 (95% CI 2.95-3.19)
• Death: HR 3.06 (95% CI 1.25-7.49) and HR 3.54 (95% CI 3.15-3.98)
• Either outcome: HR 2.69 (95% CI 2.19-3.30) and HR 3.07 (95% CI 2.95-3.19)

Based on worldwide obesity prevalence and infectious disease mortality data, the estimated percentage of fatal infections globally attributable to obesity (BMI ≥30) was 8.6% before the COVID-19 pandemic in 2018, 15% during the pandemic in 2021, and 10.8% in the post-pandemic period in 2023, reported Solja Nyberg, PhD, of the University of Helsinki in Finland, and colleagues in The Lancet.

"These findings suggest that approximately one in 10 infection-related deaths worldwide might be attributable to adult obesity, highlighting its substantial contribution to the global communicable disease burden," they wrote. "Effective prevention of adiposity, implementation of evidence-based weight-loss interventions, and stronger integration of obesity considerations into vaccination programs for high-risk groups could help reduce the burden of severe infections and related mortality."

What Weight Loss Does to Infection Risk

Obesity's ties to increased systemic inflammation, immune system dysfunction, and metabolic disturbances likely help drive the association with severe infections, Nyberg and colleagues noted. In addition to links to skin and soft tissue infections, obesity is a risk factor for severe outcomes with COVID, as well as pneumonia and influenza.

Research on treatments targeting obesity has shown reductions in infection rates. For example, a study of VA data suggested that adding a GLP-1 receptor agonist to treatment plans for adults with type 2 diabetes was associated with a decreased risk for severe infections, including a 12% reduced risk for bacterial infections.

The link between weight loss and risk reduction also played out in the current study. Co-author Mika Kivimäki, PhD, of University College London, told MedPage Today that people with obesity who lost weight had roughly a 20% lower risk of severe infections than those with persistent obesity.

Beyond obesity treatment, "one clear implication is that, for individuals with obesity, keeping recommended vaccinations up to date is especially important," Kivimäki noted. "Our findings may also provide expert panels with additional evidence to consider when updating vaccination policies and campaigns."

Solveig Argeseanu Cunningham, PhD, an epidemiologist at Emory University in Atlanta, told MedPage Today that given the results, "screening and asking questions of people with obesity, especially about skin-related diseases or conditions, might be even more advocated than it already is."

The greater risks of hospital-acquired infections in those with obesity means infection prevention around surgical sites, for example, is especially important for this population, she added.

For this study, the researchers analyzed data from 67,766 participants in two Finnish cohorts and 479,498 participants in the U.K. Biobank. They assessed BMI at baseline (1998-2002 in the Finnish groups and 2006-2010 in the U.K. group) and followed infection-related hospital admissions and deaths up to 2022. Mean baseline ages were 42.1 years and 57 years in the Finnish and U.K. groups, respectively, and 73.1% and 54.4% of participants were female.

At baseline, 57.8% of the Finnish group had a healthy weight (BMI 18.5-24.9), 31.3% were overweight (BMI 25-29.9), and 10.9% had obesity (BMI 30 or greater). In the U.K. Biobank group, 32.9% had a healthy weight, 42.8% were overweight, and 24.2% had obesity.

The study's main outcome was the first record of a non-fatal hospital-treated infection or a fatal infection. The analysis included 925 diagnoses classified by type of infection and pathogen type.

Different Infections, Different Risks

Obesity showed connections with most infection types, but not all. Among 10 widely studied infectious diseases, obesity was most strongly linked with skin and soft tissue infections (HR 2.8, 95% CI 2.6-2.9) and showed the weakest association with acute pharyngitis or tonsillitis (HR 1.5, 95% CI 1.3-1.7).

Two infectious diseases that showed no positive association with obesity were HIV (HR 0.9, 95% CI 0.4-2.0) and tuberculosis (HR 0.7, 95% CI 0.4-1.2). In both conditions, the researchers noted, obesity may counter adverse wasting effects and immune system impairments that come with being underweight.

Nyberg and team based their global mortality estimates on international, regional, and national obesity prevalence data and infectious disease mortality data from the Global Burden of Diseases, Injuries, and Risk Factors Study. The resulting global estimates of obesity-mortality links may be an overstatement, Argeseanu Cunningham cautioned, "but from the perspective of a U.S., North American, and European setting, these findings are right on."

Study limitations included the use of two databases that don't fully represent the populations from which they were drawn, limiting generalizability. The use of BMI as a measure may not adequately capture factors such as adiposity, metabolic dysfunction, or fat distribution. In addition, global impact estimates depended on data that may be inaccurate, especially in low-resource countries.

2026-02-10T23:29:42Z