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‘Obesity paradox’ debunked: Obese people really don’t live longer than normal weight people with heart disease, they’re just diagnosed at a younger age
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A study spanning almost four decades and involving more than 100,000 adults in Denmark found that those with an ‘overweight’ body mass index (or BMI) were more likely to live longer than those in the ‘healthy’, ‘underweight’, and ‘obese’ categories.
The results, which were published in May 2016, bring into question one of the fundamental assumptions we have about our health right now — that a ‘healthy’ BMI equals a longer life.
And it’s not the first time — a number of studies in the past have found that packing on a few extra pounds might not be so bad after all.
Before we go into any of the details, these results are definitely not an excuse to cancel your gym membership and have ice cream for breakfast. No one’s arguing that forgoing exercise and eating crap is your best shot at living a long, happy life. (Damn.)
What these results are suggesting is that we might need to rethink our definition of what the term «overweight» actually means.
The study, led by clinical biochemist Børge Nordestgaard from Copenhagen University Hospital, analysed the medical data of more than 100,000 adults in Denmark, recruited in three groups about 15 years apart.
They found that during the four decades of analysis — from 1976 to 2013 — the BMI associated with lowest risk of death increased from 23.7 to 27.
If your BMI is between 18.5 and 24.9, you’re considered normal or ‘healthy’, and if your BMI is between 25 and 29.9, you’re considered ‘overweight’. A BMI of 30 or more is classified as ‘obese’.
The study also found that those in the ‘obese’ category ended up having the same risk of death as those in the ‘normal’ range, even when factors such as age, sex, family history of disease, socio-economic status, and smoking were taken into account.
This means that in the past 40 years, the weight category associated with the longest lifespan has gone from ‘normal’ to squarely in the ‘overweight’ camp, which suggests that either our classification for ‘normal’ weight is wrong, or the link between our weight and our overall health is far more complicated than we thought.
«BMI as a number alone may not be sufficient to predict health and risk of death,» physician Rexford Ahima from the University of Pennsylvania School of Medicine, who wasn’t involved in the study, told Science News back in 2016.
«It has to be taken within context.»
The case against BMI as being the go-to metic for a healthy weight has been brewing for some time, with NFL star Tom Brady and NBA veteran Paul Pearce famously nudging the ‘obese’ category, and a study from earlier in 2016 finding that 34.4 million ‘overweight’ and 19.8 million ‘obese’ Americans were actually healthy, based on a range of cardio-metabolic health markers.
Quite simply, it looks like the body mass index is flawed.
«In the overweight BMI category, 47 percent are perfectly healthy,» said Jeffrey Hunger from the University of California, Santa Barbara, who was part of the earlier study showing American ‘overweight and ‘obese’ people were healthy.
«So to be using BMI as a health proxy — particularly for everyone within that category — is simply incorrect. Our study should be the final nail in the coffin for BMI.»
On top of that, the shift that Nordestgaard and his team found in their Danish study could signify how many of the health risks associated with a higher weight, such as high cholesterol and high blood pressure, are more effectively diagnosed and treated now than they were 40 years ago.
«So maybe you can be overweight if you have [these conditions] treated,» he told Esther Landhuis at Science News at the time.
The study does have its limitations — while the 100,000 people analysed are considered to be a good representation of the population of Copenhagen, it consisted of mostly white people, so we can’t say what these results could mean for people with other backgrounds.
«A substantial fraction of Asians, for instance, develop type 2 diabetes and heart disease despite having BMIs lower than the existing cut-off point for being overweight,» Landhuis pointed out.
But it does agree with what a number of studies have been suggesting — how long a person lives is far more complicated than the ratio of kilos to cm on their frame.
As Landhuis explained:
«In one study of type 2 diabetes patients, those with normal weight when diagnosed were more likely to die than those who were overweight or obese. And a 2013 meta-analysis of 97 studies found that being overweight was associated with lower risk of death than having a normal BMI — a surprising finding that echoed a 2005 study by the same researchers.»
Hopefully, as more studies like these are published, we’ll take a more personalised approach to health in the coming decades, so we don’t end up focusing on the wrong things when it comes to what’s best for an individual.
The results were published in JAMA.
A version of this article was first published in May 2016.
The study appears online this week in the journal Obesity.
It was conducted by researchers with Statistics Canada, McGill University, and the Kaiser Permanente Center for Health Research and funded by grants from the National Institute on Aging, the National Institute of Diabetes and Digestive and Kidney Diseases, and the Canadian Embassy.
Kaiser’s David Feeny, PhD, who was a co-author of the study, tells WebMD that there are theories, but no hard evidence, to explain why carrying a few extra pounds may add a few years to your life.
Being extremely underweight is considered a marker for poor health and frailty in older adults. Even though the researchers tried to control for this, poor health could explain why study participants who weighed the least had the biggest risk of dying.
But it is less clear why those who are overweight would have a lower risk of death than those whose weight is considered normal.
Because being overweight is a risk factor for a host of chronic diseases, including heart disease and diabetes, one theory is that their survival advantage is due to the fact that they receive more aggressive treatments to prevent these conditions.
«We tend to be quicker to prescribe statins (to lower cholesterol) and drugs to control blood pressure to patients who are overweight and we are more likely to screen them for diabetes,» says weight management expert Keith Bachman, MD.
Bachman leads Kaiser’s Weight Management Initiative, but he was not involved with the study.
Because the study only examined death risk, and not disease incidence or quality of life, the risk vs. benefit profile of carrying a few extra pounds is unclear, Bachman says.
«Good health is more than a BMI or a number on a scale,» he says. «We know that people who choose a healthy lifestyle enjoy better health.»
Feeny adds that lifestyle choices such as eating well, exercising regularly, managing stress, and treating risk factors for chronic disease may be more important for longevity than losing a few extra pounds.
«And this certainly doesn’t mean that people who are normal weight should go out and binge on ice cream to gain a few pounds,» he says. «The dairy industry might like that, but it would not be a good idea.»
People who are slightly overweight but not obese—as defined by their body mass index (BMI)— tend to live longer than their normal-weight counterparts, according to a new Danish study. But that has not always been the case. In the 1970s, the Danish data show, study subjects with the best chance of living longer tended to have a BMI in the normal range, defined as being between 18.5 and 25. Someone who is 1.65 meters (five feet, four inches) tall and weighs 68 kilograms (150 pounds) would have a BMI of 25.
At the extremes—of severe underweight or obesity—the Danish data show an increased risk of dying from all causes, particularly cardiovascular disease. The cutoff for considering whether someone is obese may be different, however, for different races and ethnicities. (All the Danes studied were white.) Asians from the Indian subcontinent are a case in point. South Asians tend to have more body fat for the same BMI compared with other groups. So the deleterious effects associated with weight gain tend to show up at lower absolute weights for them.
The new study may say more than anything else, however, about the health benefits of living in Denmark—all the participants lived in Copenhagen. Virtually all Danes are protected by a universal health care system that takes very good care of residents from the cradle to the grave. It is possible that medical advances over the past few decades in the treatment of type 2 diabetes, hypertension and high cholesterol levels have had a greater impact on people who are overweight—which increases the risk for these conditions—whereas the effect was much smaller in those of normal weight.
Despite this and other caveats, the report, which was published in JAMA The Journal of the American Medical Association, adds to the growing evidence that carrying a little bit of extra weight—especially after midlife—might not be as bad for your health as was once thought. Overall, the BMI associated with the lowest risk of dying from any cause for the Copenhagen cohorts was 23.7 in the 1970s, 24.6 in the 1990s and 27.0 in the present.
A similar upward trend showed up even in people who had never smoked and had no history of heart disease or cancer. For them, the BMI associated with lowest risk of death from all causes crept up from about 18 in the 1970s to 26.1 today.
When the researchers separated the cohorts into two age groups—younger than 60 and older than 60—the BMI that correlated with the lowest risk of death crept up a bit as people got older. In the 1970s, it was 23.5 for those who were 60 and younger and 24.4 for those who were older than 60—both still well within the normal range. From 2003 to 2013, the BMI linked to the lowest mortality was 26.7 for those 60 and younger and 27.3 for those over 60, which is just inside the overweight category.
The results echo those of several other large studies that have found that being slightly overweight appears to be protective—especially after middle age. Still, there is no way of concluding that increased weight per se is the protective factor. As with any epidemiological study, even one that is as well-designed as this one, correlation does not prove causation.
“This question has been around for at least 40 years,” says David Allison, an obesity researcher at the University of Alabama at Birmingham (UAB), who was not part of the research. The late Reuben Andres, the first clinical director of the National Institute on Aging in the U.S., brought it up in the 1980s. Katherine Flegal at the National Center for Health Statistics demonstrated the trend in national data in 2005 and international data in 2013. At this point, “it’s almost indisputable that the correlation exists,” Allison says. “What is disputable is what the correlation means.”
Maybe it’s not the weight as such, but just the ability to gain weight that is a mark of health. (Losing weight without wanting to is often a sign of illness.) And so gaining a little extra weight with age is merely a sign of overall health until you end up gaining so much weight that it is unhealthy. In that case, it would be hard to parse the statistics finely enough to show the difference.
Or maybe doctors do not treat people who have normal weight as aggressively as they do those who are overweight.mOr maybe, just maybe, it is simply harder to know what is going on in the border areas between a BMI of 25 and 27. Perhaps, for some people, a little bit of extra weight is protective; for others it isn’t—and researchers really can’t explain why. “These epidemiological studies do not give us an answer,” says Tapan Mehta, a biostatisticianat the UAB, who was not part of the study. “They give us interesting questions to go after.”
And for those of us who want answers now? “What the data clearly show across most ethnicities and races—if you are extremely obese, having treatment will be beneficial,” Mehta says. As for those with just a few extra pounds, it never hurts to eat more fruits and vegetables, get more sleep and exercise and stay tuned.
Put down that second helping of chocolate cake.
A new study debunks the «obesity paradox,» a counterintuitive finding that showed people who have been diagnosed with cardiovascular disease live longer if they are overweight or obese compared with people who are normal weight at the time of diagnosis.
Obese people live shorter lives and have a greater proportion of life with cardiovascular disease, reports a new Northwestern Medicine study.
The paper will be published Feb. 28 in JAMA Cardiology.
The new study shows similar longevity between normal weight and overweight people, but a higher risk for those who are overweight of developing cardiovascular disease during their lifespan and more years spent with cardiovascular disease.
This is the first study to provide a lifespan perspective on the risks of developing cardiovascular disease and dying after a diagnosis of cardiovascular disease for normal weight, overweight and obese individuals.
«The obesity paradox caused a lot of confusion and potential damage because we know there are cardiovascular and non-cardiovascular risks associated with obesity,» said Dr. Sadiya Khan, an assistant professor of medicine at Northwestern University Feinberg School of Medicine and a Northwestern Medicine cardiologist.
«I get a lot of patients who ask, ‘Why do I need to lose weight, if research says I’m going to live longer?»’ Khan said. «I tell them losing weight doesn’t just reduce the risk of developing heart disease, but other diseases like cancer. Our data show you will live longer and healthier at a normal weight.»
Obesity is defined as having a Body Mass Index (BMI) of 30 to 39.9; overweight is 25 to 29.9. BMI is a person’s weight divided by the square of his or her height. An overweight individual, who is 5’4″ and weighs 160 pounds, for example, would be considered overweight; a 5’4″ person who weights 190 pounds is considered obese.
Higher odds of a stroke, heart attack, heart failure or dying from heart disease, according to the study:
- The likelihood of having a stroke, heart attack, heart failure or cardiovascular death in overweight middle-aged men 40 to 59 years old was 21 percent higher than in normal weight men. The odds were 32 percent higher in overweight women than normal weight women.
- The likelihood of having a stroke, heart attack, heart failure or cardiovascular death in obese middle-aged men 40 to 59 years old was 67 percent higher than in normal weight men. The odds were 85 percent higher in obese women than normal weight women.
- Normal weight middle-aged men also lived 1.9 years longer than obese men and six years longer than morbidly obese. Normal weight men had similar longevity to overweight men.
- Normal weight middle-aged women lived 1.4 years longer than overweight women, 3.4 years longer than obese women and six years longer than morbidly obese women.
«A healthy weight promotes healthy longevity or longer healthspan in addition to lifespan, so that greater years lived are also healthier years lived,» Khan said. «It’s about having a much better quality of life.»
The study examined individual level data from 190,672 in-person examinations across 10 large prospective cohorts with an aggregate of 3.2 million years of follow-up. All of the participants were free of cardiovascular disease at baseline and had objectively measured height and weight to assess BMI. Over follow-up, researchers assessed for cardiovascular disease overall and by type, including coronary heart disease, stroke, heart failure and cardiovascular death, as well as non-cardiovascular death.
Other Northwestern authors include Dr. Donald Lloyd-Jones, senior author, and co-authors Dr. Hongyan Ning, Dr. John T. Wilkins, Norrina Allen, Mercedes Carnethon, and Dr. Ranya N. Sweis.
The study was supported by grants R21 HL085375 F32 HL129695 from the National Institutes of Health/National Heart, Lung, and Blood Institute.
If you dig through medical data on people’s weight and risk of dying, you may spot something curious: People who are overweight or obese appear to have a lower risk of death (during a specific time period, that is) than people with a «normal» weight.
This is the so-called «obesity paradox,» a finding that seems to fly in the face of other research that has shown that a body mass index (BMI) in the normal range is linked with the lowest risk of death during a study period, meaning it is a survival advantage.
But a new study suggests that the obesity paradox might be explained, in part, by something rather simple: how much muscle mass a person has. When researchers in the new study looked at a person’s BMI and also took muscle mass into account, they found that the risk of death from any cause was greater at nearly every level of BMI for people with low muscle mass, compared with people with more muscle mass and the same BMI level, according to the study findings, which were published April 11 in the journal PLOS One. [The Science of Weight Loss]
It’s not clear why low muscle mass is linked with a greater risk of death at nearly every BMI level. But it’s possible that having more muscle mass may protect against chronic disease or age-related disabilities, the researchers said.
BMI is calculated based on a person’s weight and height, and the number obtained provides an indication of body fatness that allows researchers to compare the relative weights of people across populations. A BMI below 18.5 is considered underweight, from 18.5 to 24.9 is «normal weight,» from 25 to 29.9 is overweight, and 30 and above is considered obese. The calculation, however, doesn’t take muscle mass into account.
When you factor in the differences in muscle mass among individuals, any protective effects associated with being overweight disappear, and the risk of death associated with obesity is in fact magnified, said study co-author Dr. Matthew Abramowitz, an associate professor of medicine at Albert Einstein College of Medicine in the Bronx, New York. In other words, the obesity paradox goes away.
For example, the study found that people with a low muscle mass and a BMI of between 22 and 24.9 had a 26 percent higher risk of death during the study period than people in the same BMI category who had more muscle mass. Similarly, people with a low muscle mass and a BMI of 25 to 29.9 were 49 percent more likely to die during the study period than people in the same BMI category who had more muscle mass.
These results show that you do not find a protective benefit from extra body fat when muscle mass is factored into the analyses, Abramowitz told Live Science.
The study looked at data collected from more than 11,500 adults who participated in the National Health and Nutrition Examination Survey (NHANES) between the years 1999 and 2004. (NHANES is a federal survey done annually to evaluate Americans’ diets and health.) All participants in that survey had their BMI calculated from their height and weight, and their muscle mass was measured by a body scan.
The results suggest that prior research using BMI has likely underestimated the risk associated with excess body fat, Abramowitz said. That’s because when BMI is used as an index, it doesn’t distinguish between a person’s fat mass and muscle mass, so having more muscle will raise BMI as much as having more body fat; this masks the risks of increased body fat, he said.
The new study’s findings show that by accounting for muscle mass in the analysis, the «obesity paradox» goes away, Abramowitz said. In other words, when people with low muscle mass are excluded from the analysis or when differences in muscle mass are taken into consideration, the risks associated with high BMI are magnified and the level of BMI linked with the greatest chance of living longer shifts downward toward a normal weight, he explained.
BMI can be a useful measurement for health professionals, but some of its limitations should be recognized, Abramowitz said.
One of the new study’s own limitations is that the findings are based on a single measure of body composition, so the study did not show why a person may have had low muscle mass at that time, the researchers noted.
Originally published on Live Science.
After a food-filled holiday, losing weight often tops the list of popular New Year’s resolutions — but a new study is shedding a different light on those extra pounds.
A U.S. study, published Wednesday in the Journal of the American Medical Association, looked at nearly 100 previous studies on weight and mortality, and found that overweight people have a significantly lower risk of premature death than those who are normal weight.
To track the finding, the team — led by the National Center of Health Statistics’ Dr. Katherine Flegal — looked at 270,000 deaths from a diverse array of countries including China, Australia, the U.S., Canada, Mexico and Israel.
The result was that people with a Body Mass Index of between 25 and 30 — considered “overweight” — were about six per cent less likely to die prematurely than those in the “normal” range, between 18.5 and 24.9. It also found that those at the lower end of “obese,” between 30 and 35 on the BMI scale, had a similar incidence of premature death as those in the normal range.
Less surprisingly, people considered “grossly obese,” with a BMI higher than 35, were 29 per cent more likely to die early than skinnier people.
BMI is calculated by dividing a person’s weight in kilograms by their height in metres squared. It is a common standard for measuring the weight of populations, but it often groups fit, young people in the overweight category due to the relative mass of muscle, explained Dr. Stephen Heymsfield on Thursday.
“There’s a correlation between body mass index and body fat, but it’s a weak correlation,” said Heymsfield, the co-author of an editorial that accompanied the study. “For example, there are people who are overweight who are not overfat… Likewise, there are people who are normal weight who are over-fat, so it’s an imprecise measure.”
He said overweight people who take refuge in the study’s results should be careful to pay attention to the details, noting it didn’t look at the overall health of overweight people, just whether they were likely to die or not.
“It doesn’t say anything about whether heart disease or diabetes is increased,” said Heymsfield, the executive director of Pennington Biomedical Research Centre in Baton Rouge, Louisiana. “It is possible that people could live longer with the disease than previously expected.”
Some scientists have suggested overweight people may be more likely to have regular doctor visits than people of normal weight, which might help detect illnesses earlier.
If the average person can take anything from this study, said Heymsfield, it’s the link between morbid obesity and death.
“I would definitely resolve not to gain more weight and go into that obese range,” he said, adding that those in the overweight range shouldn’t see the results as an excuse to ignore their health. “If you are overweight by Body Mass Index, it’s good to make sure you don’t have high blood pressure or any other risk factors.”
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