When it comes to health reporting about fat people, don't swallow everything you see.
Major news outlets on TV, radio and online lit up Monday with news
about a study claiming there was no such thing as "healthy obesity,"
which is the notion that a person can be obese according to the body
mass index chart, while at the same time be spared adverse health
effects like high blood pressure, insulin resistance and high
cholesterol levels.
For example, NBC News' headline said the study "Disputes Fat But Fit Claim," while NPR went with the headline "Overweight And Healthy: A Combo That Looks Too Good To Be True."
But, in fact, the study showed neither of those things.
The researchers, led by Dr. Caroline K. Kramer, M.D., Ph.D., of Mount
Sinai Hospital's Lunenfeld-Tanenbaum Research Institute in Toronto,
Canada, chose eight high-quality studies that tracked more than 60,000
participants' weights and metabolic health. In each of the eight
studies, participants were followed up after an extended period of time
-- ranging from three to 30 years -- to see if they had either died or
had a cardiovascular "event" like a stroke or heart attack during the
intervening years.
Kramer's team crunched the numbers by dividing the 60,000
participants into two categories: metabolically healthy and
metabolically unhealthy, based on factors like blood pressure,
cholesterol and blood sugar levels. They then created three sub-groups
of each category based on BMI: normal weight, overweight and obese. They
found that obese people who were metabolically healthy had a 24 percent
increased risk of death or cardiovascular disease when compared to the
control group of normal-weight people who were also metabolically
healthy. The meta-analysis was published Dec. 3 in the medical journal Annals of Internal Medicine.
That means NBC's headline -- "New Research Disputes Fat But Fit
Claim" -- is simply wrong because the meta-analysis didn't take physical
fitness into account, so "fat but fit" (where fit means being
physically fit) was never actually tested. NPR's is just inaccurate; in
fact, the meta-analysis showed that overweight, healthy people's risks
were so similar to the control group's risks that the difference was
statistically insignificant. In other words, overweight and healthy is not too good to be true in the context of this study.
So why did the media get this study so wrong?
Glenn Gaesser, Ph.D., an exercise and wellness professor at Arizona
State University, contends that the misinterpretation of this particular
meta-analysis actually started with the researchers themselves. Gaesser
was not involved in the meta-analysis but reviewed its findings, and
noted in an interview with The Huffington Post that the group most at
risk of cardiovascular disease or death was in fact the normal weight,
metabolically unhealthy participants. They were 214 percent (or 3.14
times) more likely to die or have a cardiovascular event, as opposed to
170 percent (2.7 times) for the unhealthy overweight and 165 percent
(2.65 times) for the unhealthy obese.
"Now that may not be statistically significant, but it does suggest
that if you're looking at only people who are [metabolically] unhealthy,
it's better to be fatter than thinner," said Gaesser.
Kramer, the study researcher, addressed this particular issue with
HuffPost, noting that it's already generally accepted that metabolically
unhealthy people have an increased risk of cardiac disease or early
death. What's more important, she stressed, is the "novel" finding that
metabolically healthy obese people are also at increased risk, despite their lack of metabolic disorders.
"We are showing very consistently that the [metabolically healthy
obese] patients are at increased risk," said Kramer. "That's why we are
stressing this finding -- this is something novel in the literature
compared to all the other sub-groups." The 24 percent increase, it
should be noted, was only found in studies that had followed up with
participants 10 years later at least, which to Kramer was a
more accurate way of assessing risk. Obese and healthy, in other words,
was simply the final stop on the road toward an obese and unhealthy
destination.
But Gaesser has a bone to pick with her there: He doesn't think
Kramer's meta-analysis of long-term studies will have lasting
significance in the medical literature on obesity and mortality because
it fails to account for one crucial factor: physical fitness.
"[The study] is junk science," said Gaesser. "It fails to factor in
the very important, well-established contribution of cardiorespiratory
fitness to overall health. The fact that they did not [include fitness]
renders this study almost uninterpretable."
Several studies support Gaesser's claim, including one recently
published meta-analysis by exercise scientist Vaughn Barry of Middle
Tennessee State University. Barry found that physical fitness,
not weight, predicted whether or not a participant had died during a
study's intervening years. He concluded that thin, unfit people had
twice the mortality risk as obese fit people.
Even an editorial in the Annals of Internal Medicine,
which praised Kramer's meta-analysis and was published alongside it,
notes that "decades of work" has shown "cardiorespiratory fitness is a
very strong predictor of total and cardiovascular mortality independent
of BMI" and called for a broader definition of wellness that isn't
limited to BMI.
"Fitness could have changed the entire outcome of this study,"
Gaesser said. "To not consider that in this day and age is
unconscionable."
In the text of Kramer's meta-analysis, she notes that the study's
limitations include not accounting for physical activity or smoking
habits. But for Gaesser, simply listing the lack of fitness data as a
"limitation" isn't good enough.
"This study, statistically speaking, assumes that all fat people, all
thin people and everyone in between are of equal fitness, equal
physical activity levels and have the same diets," Gaesser said. "And
that's just an absurd assumption."
"Ideally, you should look at metabolic factors, weight and fitness,"
conceded Kramer. "But this is a question for future studies."
Psychologist Deb Burgard, Ph.D., who counsels people with eating
disorders, is also troubled by the meta-analysis's reception in
mainstream media. In an email to HuffPost, she bemoaned the fact that
practically all of the news stories about the meta-analysis conclude
with some kind of exhortation for overweight people to shed pounds.
"The study is silent on the health impact of pursuing weight loss,
because it does not compare people who were fat who lost weight to
people who are still fat," she wrote. In fact, she continued, fat people
who repeatedly try to lose weight are more likely to yo-yo diet, or
weight-cycle, than they are to maintain weight loss permanently. And
because weight-cycling has been linked to cardiac disease
and other problems, overweight people who are metabolically healthy
could increase their risks of the very diseases they tried to avoid in
the first place if they lose weight and gain it back again.
The takeaway for fat people? Keep on trucking when it comes to
increasing your physical activity, and don't get discouraged by
headlines that seem to make weight the single determining factor in
living a long, healthy life.
"It's much easier to get a fat person fit than it is to get a fat
person thin," concluded Gaesser. And that's a good thing, because
fitness may be much more rewarding than thinness alone.
