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Being overweight cuts the risk of death – for some

3 January, 2013

Natural Health News — Being overweight is bad – right?

Well, maybe not as bad as we thought according to a new analysis in the Journal of the American Medical Association (JAMA).

In a review that included approximately 3 million adults from around the world, relative to normal weight, being overweight, even to the point of obesity was associated with significantly lower risk of death from all-causes.

These results, which are not unique, challenge deeply entrenched medical thinking – as well as the foundations upon which a multi-billion pound global weight loss industry is built.

In addition, estimates of the risks associated with normal weight, overweight, and obesity drive many medical decisions such as what drugs are prescribed and what surgeries and other procedures are recommended. Since each of these actions carries with it the risk of adverse effects, knowing the real risks is important.

The US researchers analysed 97 high quality studies that that included people from the United States, Canada, Europe, Australia, China, Taiwan, Japan, Brazil, Israel, India and Mexico. What they were looking for was a relationship between body mass index (BMI) and early death.

For decades doctors have relied on a grading system which says that a BMI 18-25 is normal, a BMI of greater than 25 is overweight , and a BMI of more than 30 is considered obese. Physicians’ oft repeated mantra is that the risk of dying is much greater for everyone who crosses the BMI 25 threshold.

Not all overweight is the same

In general this was the conclusion of this analysis which found an overall 18% higher risk of death associated with a BMI of over 25.

However the researchers did something that few others have done, which is to not lump all overweight people into one  single category but to further divide those with a BMI of over 25 into different grades. Thus:

  • Normal weight:  BMI 18.5 and 25
  • Overweight: BMI  25 and 30
  • Grade 1 Obesity:  BMI 30 and 35
  • Grades 2&3 Obesity:  BMI greater than 35

What they found was:

  • Those classed as Overweight had a 6% lower risk of death
  • Those classed as Grade 1 Obese had a 5% lower risk of death
  • Those classed as Grades 2 & 3 Obese had a 29% increased risk of death

In other words, compared to a person of normal weight, a person needed to be morbidly obese to be at a significant risk of death. The authors note that  these findings suggest that generalised warnings about the risk of death associated with being overweight may be greatly overstated and certainly not applicable to everyone carrying a few extra pounds.

The body of evidence

Lead researcher Katherine M. Flegal, of the National Center for Health Statistics of the US Centres for Disease, Ccontrol, has produced two previous analyses – both of which have shown similar results and which have caused huge debate amongst those whose default position is  ‘thin is good, fat is bad’.

In 2005 she found that being both very underweight (BMI of less than 18.5) and very overweight (BMI of greater than 30)  raised one’s risk of death, compared to those of normal BMI.

Then, in 2007, she produced a second study, dividing participants into three categories:

  • Underweight: BMI under 18.5
  • Overweight: BMI between 25-30
  • Obese: BMI greater than 30

What she found was, compared to those in the normal BMI range, being underweight was associated with significantly more deaths from non-cancer causes and non-cardiovascular causes (such as kidney disease, diabetes, respiratory  infections and disease and injuries), but not associated with death from cancer or cardiovascular disease.

In contrast, being overweight was associated with significantly fewer deaths from non-cancer causes and non-cardiovascular causes and was also not associated with death from cancer or cardiovascular disease.

Being obese was associated with significantly more deaths from cardiovascular disease, but did not increase the number of deaths from cancer, non-cardiovascular disease or non-cancer causes.

Only by combining the overweight and obese individuals could the study find an association between weight and increased risk of  death from diabetes and kidney disease and from cancers considered related to  weight – though there was still a decreased risk of death from all other non-cancer and non-cardivascular causes.

Beyond BMI

So how do we make sense of all this?

Responses to the study have varied with some experts suggesting that the definition of “normal” BMI should be revised, excluding its lowest ratings, which might be too thin. Others have suggested that our concepts of fat need to be re-evaluated, since not all fat is the same and not all fat is ‘bad’ or a threat to one’s health.

An editorial accompanying the latest study asked whether overweight, as defined by BMI, could even have a protective effect.

It noted that in the presence of a wasting disease, heart disease, diabetes, renal dialysis, or even with older age carrying extra weight has not been shown to increase mortality.  It continues:

“The optimal BMI linked with lowest mortality in patients with chronic disease may be within the overweight and obesity range. Even in the absence of chronic disease, small excess amounts of adipose tissue may provide needed energy reserves during acute catabolic illnesses, have beneficial mechanical effects with some types of traumatic injuries, and convey other salutary effects that need to be investigated in light of the studies by Flegal et al and others.”

If you are overweight but otherwise healthy (and happy) the chances are you don’t need to turn to crash dieting. BMI is only one very narrow measurement of how fit you are. Many other aspects of your lifestyle such as exercise, stress relief, not smoking or voluntarily taking in other poisons, and avoiding exposure to toxic chemicals may be just as influential, if not more so than how much you weigh.