If you are even moderately obese,there is a risk of dying three years earlier and if severely affected then 10 years may be reduced from the lifespan,which is equal to loss by lifelong smoking.
The largest-ever research released on Monday,on how obesity affects mortality has shown that obesity can trim years off life expectancy.
Epidemiologist Gary Whitlock of Oxford University,who led the analysis,said of the findings,”Excess weight shortens human lifespan. In countries like Britain and America,weighing a third more than the optimum shortens lifespan by about 3 years.
“For most people,a third more than the optimum means carrying 20 to 30 kilograms [50 to 60 pounds,or 4 stone of excess weight. If you are becoming overweight avoiding further weight gain could well add years to your life.”
The analysis brought together data from 57 long-term research studies mostly based in Europe or North America.
People were followed for an average of 10 to 15 years,during which 100,000 died.
The studies used Body Mass Index (BMI) to assess obesity. which is calculated by dividing a person’s weight in kilograms (kg) by the square of their height in metres (m).
If a person has a BMI of 30 to 35,then they are moderately obese; if they have a BMI of 40 to 50,they are severely obese.
In those who were moderately obese (BMI 30 to 35,which is now common),the lifespan was reduced by 3 years.
Severe obesity (BMI 40 to 50,which is still uncommon) reduced life expectancy by about 10 years; this is similar to the effect of lifelong smoking.
The research coordinated by the Clinical Trial Service Unit (CTSU) in Oxford and the results are published online today in The Lancet.
Among the 900,000 men and women in the study,mortality was lowest in those who had a BMI of 23 to 24. This means that if a person were 1.70m (5 feet 7 inches) tall,for example,his or her optimum weight would be about 70kg (154 pounds or 11 stone).
Comparing the effects of obesity with those of smoking,the study’s main statistician,Oxford University Professor Richard Peto said,”This study has shown that continuing to smoke is as dangerous as doubling your body weight,and three times as dangerous as moderate obesity.
“Changing your diet but keeping on smoking is not the way to increase lifespan. For smokers the key thing is that stopping smoking works.”
Although severe obesity is more common in North America than in Europe,in both places it is much less common than moderate obesity,which has only a third of the effect on lifespan that smoking does.
There was also a higher death rate among those who had a BMI well below 23 to 24. This hazard was much greater for smokers than for non-smokers. The exact reason for this remains unknown.
Obesity increases death rates for some types of cancer,but the main way it kills is by increasing risk of heart disease and stroke. Amongst middle-aged people in the UK,as many as one in four deaths from heart attack or stroke and one in 16 cancer deaths are due to being overweight or obese.
Leszek Borysiewicz,Chief Executive of the Medical Research Council,said,”As this study demonstrates,obesity is an increasingly serious public health problem of global significance”.
Sara Hiom,Cancer Research UK’s director of information,said,”Surveys have repeatedly shown that a worryingly high number of people simply don’t know that being overweight or obese increases the risk of a range of cancers.
“And these same surveys also suggest that those who are overweight often do not realise it. This study confirms that excess weight increases the risk of dying from cancer.”
Professor Peter Weissberg,Medical Director at the British Heart Foundation,said,”This is the latest and most convincing demonstration of the close relationship between being overweight and poor heart health,and confirms that smoking is harmful regardless of your weight”.