People who carry excess weight face 70% higher risk of death from 'serious disease', scientists warn

Professor Mika Kivimaki from UCL's Faculty of Brain Sciences, who led the investigation, stated: "Obesity is well known as a risk factor for metabolic syndrome, diabetes, cardiovascular disease, and many other chronic conditions.

"Here we have found robust evidence that obesity is also linked to worse outcomes from infectious diseases, as becoming very ill from an infection is markedly more common among people with obesity."

The investigation drew upon data from more than 540,000 participants enrolled in major cohort studies across Britain and Finland, including the UK Biobank dataset.

Researchers measured each participant's body mass index upon entry and subsequently tracked their health outcomes over an average period spanning 13 to 14 years.

The scope of the analysis was remarkably comprehensive, encompassing 925 distinct bacterial, viral, parasitic and fungal infections.

Scientists examined ten prevalent infectious conditions in greater depth, ranging from influenza and Covid-19 to pneumonia, gastroenteritis and urinary tract infections.

Crucially, the connection between excess weight and severe infection outcomes remained consistent regardless of which obesity measurement was employed, whether BMI, waist circumference or waist-to-height ratio.

For the majority of these common ailments, those with obesity demonstrated significantly elevated rates of hospitalisation and mortality compared to individuals with healthy BMI readings, though notably HIV and tuberculosis proved exceptions to this pattern.

The risk escalated dramatically with increasing weight, with those possessing a BMI of 40 or above facing triple the likelihood of severe infection compared to their healthy-weight counterparts.

Importantly, this association persisted even among obese individuals without metabolic syndrome, diabetes or cardiovascular disease, suggesting the link cannot be attributed solely to related chronic conditions.

Professor Kivimaki explained: "Our findings suggest that obesity weakens the body's defences against infections, resulting in more serious diseases.

"People may not get infected more easily, but recovery from infection is clearly harder."

The findings carry particular significance for Britain, where researchers estimate that one in six infection-related deaths can be attributed to obesity, a figure that rises to 26 per cent in the United States.

Encouragingly, the study revealed that shedding excess weight can diminish the risk of severe infections by approximately 20 per cent among those who successfully reduce their BMI.

The study's first author, Dr Solja Nyberg from the University of Helsinki, commented: "To reduce the risk of severe infections, as well as other health issues linked with obesity, there is an urgent need for policies that help people stay healthy and support weight loss, such as access to affordable healthy food and opportunities for physical activity.

"Furthermore, if someone has obesity, it is especially important to keep their recommended vaccinations up to date."