Researchers from the World Health Organisation followed 2.6million people’s BMI since 2009 to see the impact of their lifestyles on their health. They discovered people who are obese aged between 18 and 40 are at risk of 18 different cancers – five more than previously believed.

The new diseases linked to people’s weight are leukaemia, non Hodgkin lymphoma as well as head and neck and bladder cancers, says the study published in Nature Communications.

Dr Heinz Freisling, from the International Agency for Research on Cancer and one of the study’s co-leaders, said: “The results of our study support a re-evaluation of the cancer burden associated with overweight and obesity, which currently is likely underestimated.”

Of the millions of people examined over the period, some 225,396 were diagnosed with cancer.

The co-authors wrote: “This study shows that longer duration, greater degree, and younger age of onset of overweight and obesity during early adulthood are positively associated with risk of 18 cancers, including leukaemia, non-Hodgkin lymphoma, and among never-smokers, head and neck, and bladder cancers which are not yet considered as obesity-related cancers in the literature.

“Our findings seem to indicate that longer exposures to overweight and obesity (with or without accounting for the degree of overweight and obesity), as well as developing overweight and obesity at younger ages in early adulthood might increase cancer risk.

“Our findings support public health strategies for cancer prevention focusing on preventing and reducing early overweight and obesity.”

Commenting on the study, Dr Panagiota Mitrou, director of research, policy and innovation at World Cancer Research Fund, said: “This large study has future public health implications since additional cancers, such as leukaemia and non-Hodgkin lymphoma, have been shown to be linked with overweight and obesity.

“Our own evidence shows maintaining a healthy weight throughout life is one of the most important things people can do to reduce their cancer risk, and early prevention in adulthood is key.”

Last month it was revealed the number of children admitted to hospital due to obesity has surged by 40% in a year.

Almost 9,000 under-17s were admitted to hospital with a secondary diagnosis of obesity in England.

Separate data for 2021/22 showed 34 toddlers aged under four were taken to hospital because of a primary diagnosis of obesity.

The latest surge in obesity admissions comes after it fell during the pandemic.