Being obese can take years off your life and in some cases may be as dangerous as smoking, a new study says.
The huge study concludes that for every five points above an ideal body mass index, a person's premature death risk rises by about one-third.
Researchers combined 57 studies focusing on almost 900,000 adults in North America and Europe to analyze the relationship between BMI and the risk of dying from particular diseases.
BMI is calculated from a person's weight and height and is considered a simple and reliable way of measuring body weight. For this study, an ideal body weight was defined as a body mass index of 22.5 to 25.
The study found that an increase of BMI by five points over normal -- from 25 to 30 -- increased the odds of death:
- from heart disease or stroke by 40 per cent
- from diabetes, liver disease or kidney disease by 60-120 per cent
- from lung disease 20 per cent
- from cancer 10 per cent
For those with moderate obesity - a BMI between 30 and 35 -- the added pounds shortened the average lifespan by two to four years.
For those at extreme levels of obesity -- BMI of 40 to 45 -- the added pounds shortened the average lifespan by eight to 10 years -- comparable to the effects of smoking.
There was also a higher death rate among those who had a BMI well below the ideal range. This was due mainly to smoking-related diseases, the authors said while noting that further study is needed to understand the reasons behind the finding.
The results are published in an article on The Lancet website and will appear in an upcoming edition of the journal.
One of the study authors, Dr. Gary Whitlock of the Clinical Trial Service Unit at the University of Oxford, UK, says the findings are further proof that obesity excess weight shortens life expectancy.
"Weighing a third more than the optimum shortens lifespan by about three years. For most people, a third more than the optimum means carrying 20 to 30 kilograms (50 to 60 pounds) of excess weight.
"If you are becoming overweight or obese, avoiding further weight gain could well add years to your life.''
