BEING fat is almost as likely as smoking to cause cancer, say scientists.
Excess weight triggers 12 per cent of cases — double the number previously thought — and just below the 15 per cent linked to fags.
NHS chiefs say it means that Britain’s obesity crisis will cause an extra 360,000 cancer cases in the next decade.
Experts from the International Agency for Research on Cancer arrived at the findings with one of the first studies on how obesity genes affect tumour risk.
Lead researcher Paul Brennan said: “Our current predictions that around six per cent of cancers are caused by excess weight are an important underestimate. “It is closer to the effect of tobacco, which is about 15 per cent.”
NHS boss Simon Stevens said in May that putting on excess weight — two in three British adults are too fat — was the “new smoking”.
Referring to the study, he said: “Many people don’t yet realise that obesity causes cancer and now there is evidence that it’s a graver danger than first thought.
“If we continue to pile on the pounds we’re heading for thousands more avoidable cancer deaths every year.”
Being overweight raises the risk of 13 cancers as extra fat sends signals to cells to divide more often, causing tissue damage.
The Royal College of Physicians said the analysis, in the International Journal of Epidemiology, provided further evidence of the “potentially devastating impact of obesity”.
It urged ministers to control the availability and affordability of fatty foods through regulation and taxation.