Being obese at the age of 40 can knock seven years of a person's life expectancy, new research has revealed. Dutch researchers analysed data from just under 3,500 volunteers in the US town of Framingham, Massachusetts from 1948 to 1990. The research, which is published in the journal Annals of Internal Medicine, found that even if some of the weight was lost later on in life, a person who was obese at 40 would still risk dying earlier than someone of normal weight.