Obesity research confirms
long-term weight loss almost impossible
No known cure for obesity except surgically
shrinking the stomach
By Kelly
Crowe, CBC News Posted: Jun 04, 2014 5:00 PM ET
Last Updated: Jun 04, 2014 10:34 PM ET
The nasty
reality is that humans are efficient biological machines. "We have evolved
not to lose weight." (Reuters)
Kelly
Crowe
Medical science
Kelly
Crowe is a medical sciences correspondent for CBC News, specializing in health
and biomedical research. She joined CBC in 1991, and has spent 25 years
reporting on a wide range of national news and current affairs, with a
particular interest in science and medicine.
Related Stories
External Links
(Note:
CBC does not endorse and is not responsible for the content of external links.)
There's a
disturbing truth that is emerging from the science of obesity. After years of
study, it's becoming apparent that it's nearly impossible to permanently lose
weight.
As
incredible as it sounds, that's what the evidence is showing. For psychologist
Traci Mann, who has spent 20 years running an eating lab at the University of
Minnesota, the evidence is clear. "It couldn't be easier to see," she
says. "Long-term weight loss happens to only the smallest minority of
people."
We all
think we know someone in that rare group. They become the legends — the
friend of a friend, the brother-in-law, the neighbour — the ones who
really did it.
But if we
check back after five or 10 years, there's a good chance they will have put the
weight back on. Only about five per cent of people who try to lose weight
ultimately succeed, according to the research. Those people are the outliers,
but we cling to their stories as proof that losing weight is possible.
"Those
kinds of stories really keep the myth alive," says University of Alberta
professor Tim Caulfield, who researches and writes about health misconceptions.
"You have this confirmation bias going on where people point to these very
specific examples as if it's proof. But in fact those are really
exceptions."
Our
biology taunts us, by making short-term weight loss fairly easy. But the weight
creeps back, usually after about a year, and it keeps coming back until the
original weight is regained or worse.
This has
been tested in randomized controlled trials where people have been separated
into groups and given intense exercise and nutrition counselling.
Even in
those highly controlled experimental settings, the results show only minor
sustained weight loss.
When
Traci Mann analyzed all of the randomized control trials on long-term weight
loss, she discovered that after two years the average amount lost was only one
kilogram, or about two pounds, from the original weight.
Tiptoeing around the truth
So if
most scientists know that we can't eat ourselves thin, that the lost weight
will ultimately bounce back, why don't they say so?
Tim
Caulfield says his fellow obesity academics tend to tiptoe around the truth.
"You go to these meetings and you talk to researchers, you get a sense
there is almost a political correctness around it, that we don't want this
message to get out there," he said.
Last
fall, the Dubai government launched a 30-day weight loss challenge called
"Your Weight in Gold" to encourage dieters and combat growing obesity
in the Gulf Arab emirate. It should probably save its money if the current
science is right. (Reuters)
"You'll
be in a room with very knowledgeable individuals, and everyone in the room will
know what the data says and still the message doesn't seem to get out."
In part,
that's because it's such a harsh message. "You have to be careful about
the stigmatizing nature of that kind of image," Caulfield says.
"That's one of the reasons why this myth of weight loss lives on."
Health
experts are also afraid people will abandon all efforts to exercise and eat a
nutritious diet — behaviour that is important for health and longevity — even
if it doesn't result in much weight loss.
Traci Mann
says the emphasis should be on measuring health, not weight. "You should
still eat right, you should still exercise, doing healthy stuff is still
healthy," she said. "It just doesn't make you thin."
We are biological machines
But
eating right to improve health alone isn't a strong motivator. The research
shows that most people are willing to exercise and limit caloric intake if it
means they will look better. But if they find out their weight probably won't
change much, they tend to lose motivation.
'Healthy stuff is still healthy,
it just doesn't make you thin'- Traci Mann, University of Minnesota
That
raises another troubling question. If diets don't result in weight loss, what
does? At this point the grim answer seems to be that there is no known cure for
obesity, except perhaps surgically shrinking the stomach.
Research
suggests bariatric surgery can induce weight loss in the extremely obese,
improving health and quality of life at the same time. But most people will
still be obese after the surgery. Plus, there are risky side effects, and many
will end up gaining some of that weight back.
If you
listen closely you will notice that obesity specialists are quietly
adjusting the message through a subtle change in language.
These
days they're talking about weight maintenance or "weight management"
rather than "weight loss."
Michelle
Obama has been on an eat better campaign ever since her husband was elected to
the White House. An estimated 2.1 billion people on the planet are now
considered overweight or obese. (Reuters)
It's a
shift in emphasis that reflects the emerging reality. Just last week the
headlines announced the world is fatter than it has ever been, with 2.1
billion people now
overweight or obese, based on an analysis published in the online issue of the
British medical journal The Lancet.
Researchers
are divided about why weight gain seems to be irreversible, probably a
combination of biological and social forces. "The fundamental
reason," Caulfield says, "is that we are very efficient biological
machines. We evolved not to lose weight. We evolved to keep on as much weight
as we possibly can."
Lost in
all of the noise about dieting and obesity is the difficult concept of
prevention, of not putting weight on in the first place.
The
Lancet study warned that more than one in five kids in developed countries are
now overweight or obese. Statistics Canada says close to a third of Canadian
kids under 17 are overweight or obese. And in a world flooded with food, with
enormous economic interest in keeping people eating that food, what is required
to turn this ship around is daunting.
"An
appropriate rebalancing of the primal needs of humans with food availability is
essential," University of Oxford epidemiologist Klim
McPherson wrote in
a Lancet commentary following last week's study. But to do that, he suggested,
"would entail curtailing many aspects of production and marketing for food
industries."
Perhaps,
though, the emerging scientific reality should also be made clear, so we can
navigate this obesogenic world armed with the stark truth — that we are
held hostage to our biology, which is adapted to gain weight, an old
evolutionary advantage that has become a dangerous metabolic liability.