Every extra two pounds an overweight person carries cuts their life expectancy by two months, new research reveals.
Holding excess weight may shorten a person's life by raising their risk of coronary artery disease, according to the researchers.
Smoking has the greatest impact on shortening people's lives, with a packet of cigarettes a day knocking off seven years, the research adds.
The study also revealed every additional year an individual spends in further education extends their lifespan by 11 months by making them more aware of the dangers of smoking.
Study author Dr Peter Joshi from the University of Edinburgh, said: '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.'
Every extra two pounds an overweight person carries cuts their life expectancy by two months
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LOSING WEIGHT COULD BE AS SIMPLE AS SKIPPING BREAKFAST: FASTING UNTIL LUNCH CUTS MORE THAN 300 CALORIES
Losing weight could be as simple as skipping breakfast, research suggested earlier this month.
Fasting until lunch causes people to eat around 353 fewer calories a day, a study found.
Study author Dr Keith Tolfrey said: 'There is a common belief that breakfast is the "most important meal of the day".
'However, around one third of children and adolescents in many countries skip breakfast regularly.'
The findings from the Universities of Loughborough and Bedfordshire support a growing body of evidence that restricting calories, via fasting, boosts weight loss by reducing people's calorie intake and regulating hormones involved in fat storage.
How the research was carried out
The researchers analysed 25 studies from Europe, Australia and North America with a total of 606,059 people.
The study's participants' genetic and lifespan information was investigated.
Excess weight and smoking shorten people's lifespan
Results reveal people who are overweight reduce their life expectancy by two months for every additional 2lbs they carry.
Carrying excess weight may shorten a person's life by raising their risk of coronary artery disease.
The study also found every extra year a person spends in further education extends their life expectancy by 11 months.
This is thought to be due to educated people being more aware of the dangers of smoking, which has the greatest impact on lessening lifespan.
People who get through a packet of cigarettes a day knock on average seven years off their life expectancy.
In terms of genetics, a gene that influences blood cholesterol levels can reduce a person's lifespan by eight months, while a gene associated with the immune system can extend someone's life by around half a year.
Dr Joshi said: '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.'
One positive finding was that those who continue their education after school live longer.
Co-author Professor Naveed Sattar, from Glasgow University, said: ‘The message is that losing an achievable amount of weight could bring you extra years of life, which is a good incentive.
‘We know weight gain cuts people’s lives short by increasing their blood pressure, blood fats and diabetes risk, which raises their risk of heart attack and stroke. This study shows we could learn something from the Japanese, one of the thinnest nations in the world [which] has the longest-living people.’
Most studies on early deaths in overweight people are flawed. Weight alone might not be to blame as those who eat badly are often unhealthy in other ways, for example exercising less or drinking more alcohol.
The latest research aims to be more precise by looking at genes linked to weight gain, of which there are hundreds.
Researchers say that while it may appear we overeat from greed or lack of willpower, in fact for some their genes play an important role.
For example the genes could disrupt signalling between the gut and brain, so people do not realise they are full, and may also affect self-control when it comes to diet. Previous studies show genes can predict how much weight people will gain.
To determine how this cuts lives short, the researchers looked at the parents who shared half the genes of the study’s subjects and the age at which they died.
The findings were published in the journal Nature Communications.