Gaining weight as an adult increases the risk of cancer by up to five times, according to research involving more than 600,000 patients.

Obesity can cause 13 different cancers and is thought to be linked to another eight. But less is known about the impact on cancer risk of the amount of weight put on – and when in life it is gained.

To find out, researchers at Lund University in Sweden analysed weight and cancer incidence data from more than 600,000 men and women and found there was no safe age to get heavier.

The study, presented at the European Congress on Obesity in Istanbul, measured the weight of more than 250,000 men and just under 380,000 women an average of four times between the ages of 17 and 60. It also tracked their cancer diagnoses until 2023.

The authors found that increased cancer risk – both overall and for many specific cancer types – was associated with heavier initial weight in early adulthood as well as weight gained during adulthood.

Anton Nilsson, lead author and an associate professor at Lund, said: “The higher the starting weight and the greater the weight gain, the higher the cancer risk tended to be.”

Men who became obese before the age of 30 had a five times higher risk of liver cancer, double the risk of pancreatic cancer and kidney cancer, and a 58% increased risk of colon cancer than those who remained slim. Women who developed obesity before the age of 30 were at a four-and-a-half times increased risk of endometrial cancer, a 67% higher risk of pancreatic cancer, double the risk of kidney cancer and a 76% increased risk of meningioma than those who never became obese.

For those who put on weight later in life, there were gender differences. For women, putting weight on after the age of 30 was strongly associated with increased relative risks of endometrial cancer, postmenopausal breast cancer and meningioma – cancers for which sex hormones are considered a primary causative factor. Colon cancer was also strongly linked to female weight changes.

Among men, the associations with obesity-related cancers were instead stronger for weight gains below the age of 45, most clearly for oesophageal and liver cancer. Nilsson said this was “perhaps because earlier weight gain allows more time for biological processes such as inflammation and raised insulin levels to act on susceptible tissues”.

Those who put on the most weight (an average of 32kg [5 stone]) were 7% more likely to develop cancer than those who gained the least – an average of 8kg. Men who gained the most weight were nearly three times more likely to develop liver cancer and more than twice as likely to develop oesophageal cancer than those who put on the least.

They also had three times the risk of pituitary tumours and a more than 50% increased risk of renal cell carcinoma, gastric cardia and colon cancers.

Women who gained the most weight had nearly four times the risk of endometrial cancer and double the risk of pituitary tumours as well as a significantly higher risk of renal cell carcinoma (91%), postmenopausal breast cancer (42%), meningioma (32%) and colon cancers (31%).

Even those who gained lower amounts of weight still had a higher risk of developing cancer, the study found, underlying the need to keep excess weight off.

‘‘While our results do not speak to any specific interventions or behaviours, they highlight the importance of maintaining a stable, healthy weight throughout adult life,” Nilsson added.

Responding to the findings, Megan Winter of Cancer Research UK said: “Overweight and obesity is the second biggest cause of cancer in the UK. The government should do more to help people find it easier to keep slimmer.

“Further measures to restrict the advertising and promotion of junk food, introduce mandatory reporting on healthy food sales, and make nutritious food more accessible to everyone could all help reduce obesity rates and improve health across the country.”