Health myths: Being a bit overweight shortens life

reposted from: http://www.newscientist.com/article/mg21929311.100

crabsallover highlights, key points, comments / links.


Health myths: Being a bit overweight shortens life
26 August 2013 by Caroline Williams

Let's be clear – being seriously obese is bad for your health. A body mass index of over 40 increases the risk of type 2 diabetes, heart disease and certain cancers and increases the risk of dying from any cause by up to 29 per cent. This is not a health myth.

But carrying just a few extra pounds, far from being a one-way ticket to an early grave, seems to deter the grim reaper, according to a recent review of nearly a hundred studies involving nearly 3 million people. The review, led by Katherine Flegal of the US Centers for Disease Control in Hyattsville, Maryland, reported earlier this year that being "overweight" – defined as having a body mass index (BMI) of 25 to 29 – seems to have a protective effect, with a 6 per cent ...

details: http://www.ncbi.nlm.nih.gov/pubmed/23280227
RESULTS:
Random-effects summary all-cause mortality Hazard Ratios (HRs) for overweight (BMI of 25-<30), obesity (BMI of ≥30), grade 1 obesity (BMI of 30-<35), and grades 2 and 3 obesity (BMI of ≥35) were calculated relative to normal weight (BMI of 18.5-<25). The summary HRs were 0.94 (95% CI, 0.91-0.96) for overweight, 1.18 (95% CI, 1.12-1.25) for obesity (all grades combined), 0.95 (95% CI, 0.88-1.01) for grade 1 obesity, and 1.29 (95% CI, 1.18-1.41) for grades 2 and 3 obesity. These findings persisted when limited to studies with measured weight and height that were considered to be adequately adjusted. The HRs tended to be higher when weight and height were self-reported rather than measured.

CONCLUSIONS AND RELEVANCE:
Relative to normal weight, both obesity (all grades) and grades 2 and 3 obesity were associated with significantly higher all-cause mortality. Grade 1 obesity overall was not associated with higher mortality, and overweight was associated with significantly lower all-cause mortality. The use of predefined standard BMI groupings can facilitate between-study comparisons.

Full details: http://jama.jamanetwork.com/article.aspx?articleid=1555137

Comment: http://jama.jamanetwork.com/article.aspx?articleid=1555137#COMMENT - lists strengths and weakness.

"... Our study also has limitations. It addresses only all-cause mortality and not morbidity or cause-specific mortality. It addresses only findings related to BMI and not to other aspects of body composition such as visceral fat or fat distribution..."

NHS Direct review

"However, a slight increase in lifespan doesn’t necessarily equate to an increased quality of life. Even being ‘just’ overweight can increase the chance of developing long-term health conditions, which while may not be fatal, can make life a lot less enjoyable."

and

"The headlines also did not make clear that the increase in life expectancy in people who were overweight or ‘mildly’ obese was modest – they were only 6% less likely to have died by the end of the study period than those of a healthy weight."

Methods

This systematic review included a meta-analysis of 97 studies comprising data on 2.88 million people and 270,000 deaths.

Conclusion

This systematic review provides high-quality evidence that obesity grades 2 and 3 are associated with higher death rates from any cause compared to normal weight individuals (around 30% increased risk). However, it also shows that lower grades of obesity (grade 1) do not increase the risk of death relative to normal-weight individuals and, in fact, overweight people had a small but significant reduction in their risk of death in the region of 6%.

The strengths of this review include the large number of studies it included and its standardised approach to searching and extracting data from the literature. Hence, we can be reasonably confident these results reflect reality.

However, a limitation of the study is that it only assessed the risk of dying from any cause (‘all-cause’ mortality), rather than death from specific diseases such as cancer, heart disease or diabetes. The association between weight and risk of death for different disease categories may vary. Disability and living with long-term diseases are also important to people and some conditions such as diabetes may show stronger links with weight at lower thresholds of BMI.

The review also crucially chose BMI as the measure of weight, which has been mistakenly taken by the media to mean an accurate measure of unhealthy ‘fatness’. BMI is a pragmatic choice to assess weight but it does not account for other known disease and death risk factors such as differing fat levels, fat distribution, muscularity, nutritional balance and others. BMI is also an imperfect measure of fatness as it only measures weight and height. Hence, those who are overweight are not all necessarily overweight because they are carrying excess fat. For instance, someone who is very muscular can have a high BMI and therefore be categorised as overweight.

Other measures such as waist circumference offer alternative ways of quickly estimating a person’s body fat levels and whether they are of a healthy weight. In practice, BMI is not the only measure used when establishing risk of disease or death. Doctors will be checking for a host of risk factors like high blood pressure, high cholesterol and high blood glucose levels in addition to BMI and/or waist circumference. Hence, the BMI category is only one of many measures used by a doctor to assess health, and by no means the best.

The finding that overweight individuals were at slightly less risk of dying than their normal-weight counterparts had been reported in research before (this is often referred to as the obesity paradox).

Possible explanations why a bit of extra weight may extend life include:

• People with more fat reserves to rely on may survive better if they lose weight due to ill health as they get older.
• Problems associated with being overweight (high blood pressure and diabetes) are picked up and treated earlier in overweight people compared with normal weight, as doctors are more vigilant of risk factors in overweight people. This treatment improves their health overall.

However, it is important to note that these are largely unsubstantiated theories and have not been further explored or proven.

The bottom line is that being obese (all categories combined) increased the chance of dying compared to those with a normal BMI. This was not the case for overweight individuals or the lowest category of obesity (grade 1) on its own.

It is important to consider that individual risk factors for developing disease and death will vary person to person and BMI is only one of many measures used to assess the risk of developing disease in the future.

Even if you choose to ignore the limitations of this research, it would be unwise to interpret its findings as proof that being overweight is ‘healthy’ – rather it may be slightly less unhealthy than perceived.

source: http://www.nhs.uk/news/2013/01january/pages/overweight-people-live-longer-study-claims.aspx

Now Doctors Say It's Good to be Overweight

reposted from: http://www.alternet.org/healthwellness/67692/?page=entire

Now Doctors Say It's Good to be Overweight

By David Usborne, The Independent UK. Posted November 13, 2007.

After years of anti-obesity public health advice, a major new study causes an outcry by concluding that the moderately overweight live longer.

A startling new study by medical researchers in the United States has caused consternation among public health professionals by suggesting that, contrary to conventional wisdom, being overweight might actually be beneficial for health.

The study, published yesterday in the respected Journal of the American Medical Association, runs counter to almost all other advice to consumers by saying that

carrying a little extra flab -- though not too much -- might help people to live longer.

Struggling dieters, used to being told that staying thin is the best prescription for longevity, are likely to be confused this morning if not heartily relieved. While being a bit overweight may indeed increase your chances of dying from diabetes and kidney disease -- conditions that are often linked with one another -- the same is not true for a host of other ailments including cancer and heart disease, the report suggests.

In fact,

scanning the whole gamut of diseases that could curtail your life, being over weight is, on balance, a good thing. The bottom line, the scientists say, is that modestly overweight people demonstrate a lower death rate than their peers who are underweight, obese or -- most surprisingly -- normal weight.

The findings will be hard to dismiss. They are the result of analysis of decades of data by federal researchers at the Centres for Disease Control and Prevention (CDC) in Atlanta, Georgia. This is not a study from a fringe group of scientists or sponsored by a fast-food chain.

Being overweight, the report asserts in its conclusions, "was associated with significantly decreased all-cause mortality overall".

"The take-home message is that the relationship between fat and mortality is more complicated than we tend to think," said Katherine Flegal, the lead researcher. "It's not a cookie-cutter, one-size-fits-all situation where excess weight just increases your mortality risk for any and all causes of death."

That the CDC has even published the report and thus threatened to muffle years of propaganda as to the health benefits of staying slender has enraged some medical experts.

"It's just rubbish," fumed Walter Willett, the professor of epidemiology and nutrition at the Harvard School of Public Health. "It's just ludicrous to say there is no increased risk of mortality from being overweight."

Not that the CDC results are an invitation to throw caution to the winds and take cream with everything. The scientists are careful to stress that

the benefits they are describing are limited to those people who are merely overweight -- which generally means being no more than 30 pounds heavier than is recommended for your height -- and certainly do not carry over to those who fall into the category of obese.

Obesity has been declared one of the main threats to health in the US, including among children. Those considered obese, with a body mass index (BMI) of more than 30, continue to run a higher risk of death, the study says, from a variety of ailments, including numerous cancers and heart disease. It said that being underweight increases the risk of ailments not including heart disease or cancer.

The scientists at the CDC first hinted at the upside of being overweight a few years ago. Since then, however, they have expanded the base of their analysis, with data that includes mortality figures from 2004, the last year for which numbers were available, for no fewer than 2.3 million American adults.

Highlighting how a bit of bulge might help you, the scientists said that in 2004 there were 100,000 fewer deaths among the overweight in the US than would have been expected if they were all considered to be of normal weight.

Put slightly differently, those Americans who were merely overweight were up to about 40 per cent less likely than normal-weight people to die from a whole range of diseases and risks including emphysema, pneumonia, Alzheimer's, injuries and various infections.

Aside from escaping diseases, tipping the scales a little further may also help people recover from serious surgery, injuries and infections, Dr Flegal suggested. Such patients may simply have deeper bodily reserves to draw on in times of medical crisis.

Not everyone in the medical profession was surprised or angry about the study. "What this tells us is the hazards have been very much exaggerated," said Steven Blair, a professor of exercise science and biostatistics at the University of South Carolina, who has long argued that the case for dietary restraint has been taken too far.

"I believe the data," added Elizabeth Barrett-Connor, a professor of family and preventive medicine at the University of California, San Diego, who believes that

a BMI of 25 to 30 -- roughly the the so-called overweight range -- "may be optimal".

Critics, however, were quick to point out that

the study was concerned with mortality data only and did not take account of the quality of life benefits of keeping your weight down. The study "is not about health and sickness"

, noted the obesity researcher Barry Popkin of the University of North Carolina.

The report "definitely won't be the last word", said Dr Michael Thun of the American Cancer Society, who pointed out,

in a report released last week by the World Cancer Research Fund and the American Institute for Cancer Research, that staying slim was the main recommendation for avoiding cancer.

Others in the American medical community, while a little bemused, were withholding judgement. "This is a very puzzling disconnect," said Dr JoAnn Manson, the chief of preventive medicine at Harvard's Brigham and Women's Hospital.

The suggestion that a bit of extra weight may assist patients recovering from an infection or surgery was of no surprise to Dr Flegal. "You may also have more lean mass -- more bone and muscle," she said. "If you are in an adverse situation, that could be good for you."

In their conclusions, the authors of the study note:

"Overweight ... may be associated with improved survival during recovery from adverse conditions, such as infections or medical procedures, and with improved prognosis for some diseases. Such findings may be due to greater nutritional reserves or higher lean body mass associated with overweight."

Those of us mostly likely to benefit from a little bulge beneath the belt, the study adds, are between 25 and 59 years old, although there were also some advantages for people over 60.