More evidence for "obesity paradox"

NEW YORK Tue Jan 1, 2013 6:12pm EST

An overweight woman sits on a chair in Times Square in New York, May 8, 2012. REUTERS/Lucas Jackson

An overweight woman sits on a chair in Times Square in New York, May 8, 2012.

Credit: Reuters/Lucas Jackson

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NEW YORK (Reuters Health) - In a review of almost 100 past studies covering nearly three million people, researchers found that being overweight or slightly obese was linked to about a 6 percent lower risk of dying, compared to people considered "normal weight."

Being severely obese, however, was still tied to an almost 30 percent higher risk of death.

The idea that being somewhat overweight could be linked to better health has been dubbed the obesity paradox, even though actual obesity is generally not associated with the apparent "benefit."

"This is actually the common finding," said the new study's lead author Katherine Flegal, a senior scientist from the U.S. Centers for Disease Control and Prevention in Hyattsville, Maryland.

Her work, she said, confirms what previous analyses found - a link between being somewhat overweight and having a lower risk of death.

The paradox, as scientists have called it, is based on past findings that suggest overweight and obese people - even those with additional health problems - live longer than their thinner counterparts (see Reuters Health article of August 7, 2012 here: reut.rs/N0YvOK).

Some have argued that the pattern is a statistical one only because being thin, especially in old age, is often a sign or a result of serious illness - so the thinner people seem to have higher mortality.

The study results certainly do not give people permission to pack on extra pounds, according to Dr. Steven Heymsfield, the executive director of the Pennington Biomedical Research Center in Baton Rouge, Louisiana.

Heymsfield, who co-authored an editorial accompanying the new report, said the difference in mortality between overweight and normal weight people is probably very small.

"That's actually a very small number. It's probably only statistically significant because of the large number she had in her study," he added.

Also, there are concerns that body mass index (BMI) - a measurement of weight in relation to height - is not an accurate measure of someone's health risks.

For example, Heymsfield said a soldier may be considered overweight but still be healthy, because he or she has more muscle mass.

"It's not a good marker for body fat or health risk," he said.

There is also confusion around what BMI should be considered "normal," which is why Flegal and her colleagues conducted their analysis.

Past studies looking at the link between BMI and death used varying ranges to describe normal weight, overweight and obesity.

"There seems to be a lot of confusion about this whole area, and part of the confusion is that people are using a bunch of different categories," said Flegal.

For the new analysis, the researchers, who published their results in the Journal of the American Medical Association, used data from past studies, and classified the risks according to BMI categories accepted by the World Health Organization and the U.S. National Heart, Lung, and Blood Institute.

Those organizations consider a BMI between 18.5 and 24.9 normal weight, between 25 and 29.9 overweight, and 30 or above obese. They further subdivide the obese category, though - with a BMI between 30 and 34.9 designated grade-1 obesity, and anything above 35 grades 2 or 3.

The researchers reviewed databases of medical research and found 97 studies that looked at weight and mortality risk. Combined, Flegal and her colleagues had information on about 2.9 million people from around the world and 270,000 deaths.

Being obese - in general - was linked to an 18 percent greater risk of death, compared to being normal weight. Being severely obese - grades 2 and 3 - was linked to a 29 percent greater risk of death.

However, being merely overweight was linked to a 6 percent decreased risk of death compared to a normal weight person, while being slightly (grade 1) obese was linked to a 5 percent lower risk.

The study cannot say why there seems to be a link between being overweight or slightly obese and a lower risk of death.

"We don't have the data to look at the physiological mechanisms, and that wasn't our goal," said Flegal.

"Our contribution - I hope - is just to summarize it to show what other articles are showing," she said.

For Heymsfield, the findings reinforce the common belief that increased weight is tied to an increased risk of death, but highlights the fact that someone classified as "overweight" is not necessarily "very unhealthy."

On the other hand, he warns, important markers of health, such as blood pressure and cholesterol, do respond to minor changes in weight.

"So gaining that extra 10 or 20 pounds can put you into a dangerous category, and it's important to find out if you're one of those people," he said.

SOURCE: bit.ly/JOTmp1 Journal of the American Medical Association, online December 31, 2012.

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Comments (7)
jrj906202 wrote:
Who cares.You know what your health is by how much pain you’re in and how well your body functions.Get enough exercise,eat mostly unprocessed food,not too much fat or sugar and you should be OK.

Jan 02, 2013 11:51am EST  --  Report as abuse
eMJayy wrote:
Sounds far too simplistic in my view. We keep using terms like ‘ideal weight’ and ‘overweight’ to create sweeping generalizations, but we ignore the fact that an individual’s fat distribution is also playing a major role in determining relative risk.

Consider this. You can have two individuals with the same BMI and both are considered ‘overweight’ based on their BMI. One has that extra body fat largely confined to areas of the body that have been shown to have lower association with the long term complications of obesity. The other has that fat piled up in more risky areas. The overall health risk to these two individuals would not be the same, despite the fact that they have the same BMI and are both overweight.

When we gain weight, we don’t really pile on the fat in exactly the same proportions. Some people are going to initially pile on the extra weight in a body distribution that is healthier than others. BMI doesn’t take this into account and neither does the term ‘overweight’. As you gain further body fat and become obese, that healthy fat distribution that you may have had as an ‘overweight’ individual goes out the window as everyone will tend to pack pounds wherever it can fit on their body.

Jan 02, 2013 12:46pm EST  --  Report as abuse
Adipofat wrote:
Purported obesity epidemic promotes the “obesity=disease” equation. Obesity is an adipose tissue expansion and aesthetically might not fit society’s “ideal” body shape but medicalizing obesity is pathologizing fat. Excess body fat can indeed pose a health. However, in some circumstances being obese is an advantage in some chronic diseases. The first think we should be doing is to define when obesity has to be treated hence shifting the focus from weight management to health promotion

Jan 02, 2013 2:48pm EST  --  Report as abuse
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