The study found that moderately obese people die, on average, three years earlier than expected. Meanwhile overweight people lose one year of their expected life span.
In overweight and obese men, the association with premature death before the age of 70 was three times stronger than for women.
Dr Emanuele Di Angelantonio, from the University of Cambridge, said: “On average, overweight people lose about one year of life expectancy, and moderately obese people lose about three years of life expectancy.
“We also found that men who were obese were at much higher risk of premature death than obese women.
“This is consistent with previous observations that obese men have greater insulin resistance, liver fat levels, and diabetes risk than women.”
The World Health Organisation estimates that 1.3 billion adults worldwide are overweight and 600 million are obese.
Co-author of the study, Professor Sir Richard Peto from Oxford University, said that obesity is now the second highest cause of premature death in Europe and North America.
“Smoking causes about a quarter of all premature deaths in Europe and in North America, and smokers can halve their risk of premature death by stopping,” he explained.
“But, overweight and obesity now cause about one in seven of all premature deaths in Europe and one in five of all premature deaths in North America.”
Professor Peter Weissberg, medical director at the British Heart Foundation, which part-funded the research, said the results show that “being overweight does have a significant impact on your health”.
He added that the research, which was published in the Lancet Journal, “strengthens arguments for public health measures to reduce obesity in our society”.