A new study has found that people who are overweight cut their life expectancy by two months for every extra kilogram (or about two pounds) of weight they carry.
The study, from researchers at the University of Edinburgh, also found that education leads to a longer life, with almost a year added for each year spent studying beyond school.
Other findings from the study show that people who give up smoking and are open to new experiences might expect to live longer.
“Our study has estimated the causal effect of lifestyle choices,” said Dr. Peter Joshi, Chancellor’s Fellow at the University of Edinburgh’s Usher Institute. “We found that, on average, smoking a pack a day reduces lifespan by seven years, whilst losing one kilogram of weight will increase your lifespan by two months.”
For the study, scientists at the University of Edinburgh analyzed genetic information from more than 600,000 people alongside records of their parents’ lifespan.
Because people share half of their genetic information with each of their parents, the researchers say they were able to calculate the impact of various genes on life expectancy.
Lifestyle choices are influenced to a certain extent by our DNA — genes, for example, have been linked to increased alcohol consumption and addiction.
The researchers said they were, therefore, able to work out which have the greatest influence on lifespan.
The method was designed to rule out the chances that any observed associations could be caused by a separate, linked factor. This enabled them to pinpoint exactly which lifestyle factors cause people to live longer, or shorter, lives.
They found that cigarette smoking and traits associated with lung cancer had the greatest impact on shortening lifespan.
For example, smoking a pack of cigarettes a day over a lifetime knocks an average of seven years off life expectancy, they calculated. But smokers who give up can eventually expect to live as long as somebody who has never smoked, they discovered.
Body fat and other factors linked to diabetes also have a negative influence on life expectancy.
The study also identified two new DNA differences that affect lifespan. The first — in a gene that affects blood cholesterol levels — reduces lifespan by around eight months. The second — in a gene linked to the immune system — adds around half a year to life expectancy.
Data for the study, published in Nature Communications, was drawn from 25 separate population studies from Europe, Australia, and North America, including the UK Biobank, a major study into the role of genetics and lifestyle in health and disease.
“The power of big data and genetics allow us to compare the effect of different behaviors and diseases in terms of months and years of life lost or gained, and to distinguish between mere association and causal effect,” said Professor Jim Wilson of the University of Edinburgh’s Usher Institute.
Source: University of Edinburgh