London, Oct 14 (IANS): Want to live a long life? Reducing excess weight and staying in shape may prolong life expectancy by two months, researchers suggested.

The study showed that people who are overweight cut their life expectancy by two months for every extra kilo of weight they carry.

Cigarette smoking and traits associated with lung cancer also had the greatest impact on shortening lifespan.

In addition, body fat and other factors linked to diabetes also have a negative influence on life expectancy, the researchers mentioned.

"Our study has estimated the causal effect of lifestyle choices. 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," said Peter Joshi, researcher at the University of Edinburgh in Scotland.

The team took the data from 25 separate population studies and analysed genetic information from more than 600,000 people alongside records of their parents' lifespan.

People share half of the genetic information with each of their parents. Therefore, certain lifestyle factors become highly influenced by some genes that further impacts life expectancy of people, like, increased alcohol consumption and addiction, the researchers explained, in the paper published in the journal Nature Communications.

The study also identified two new DNA differences that affect lifespan. The first in a gene that affects blood cholesterol levels and reduces lifespan by around eight months.

The second is a gene linked to the immune system which adds around half a year to life expectancy.

"The power of big data and genetics allow us to compare the effect of different behaviours and diseases in terms of months and years of life lost or gained, and to distinguish between mere association and causal effect," said Jim Wilson, Professor at the varsity.