The Weight Debate

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REDNOVA NEWS

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The Weight Debate

By Liebman, Bonnie

IS THAT SPARE TIRE A LIFESAVER?

" Some extra heft may be helpful, " declared The New York Times.

" Pleasantly plump may be okay, " announced ABC News.

Last April, a flurry of news reports shook the conventional wisdom

that putting on extra pounds is a health risk. " The headlines

generated tremendous controversy and confusion, " notes Walter Willett,

chair of the nutrition department at Harvard University's School of

Public Health.

Researchers at Harvard, the American Cancer Society, and elsewhere

argue that the study behind those headlines-from the Centers for

Disease Control and Prevention-was flawed.

" The CDC seriously underestimated the risk of dying in the overweight

by not adequately dealing with the bias due to smoking and disease, "

explains Thun, vice president for epidemiology and research at

the Cancer Society.

Here's the scoop on which weight is the healthiest and why.

" It seems like dj vu, " noted Harvard's Walter Willett as he opened a

symposium on Overweight, Obesity and Mortality " last May

(www.hsph.harvard .edu/weighing_the_evidence).

" It was just about 15 years ago when a scientist at the National

Institute on Aging concluded that it was good to be a little

overweight rather than normal weight, " explained Willett. " And it was

pure rubbish. "

The latest skirmish began in April, when Flegal,

on, and others from the Centers for Disease Control and

Prevention (CDC) and elsewhere analyzed the link between weight and

the risk of dying in a nationally representative survey of roughly

37,000 Americans. Their study led The New York Times to declare:

" People who are overweight but not obese have a lower risk of death

than those of normal weight, federal researchers are reporting today. "

Where does that leave a nation where two out of three adults are

overweight or obese? Confused.

" I was appalled by what I read in the newspapers when this study came

out, " Grundy told the Harvard symposium. Grundy is director of

the Center for Human Nutrition at the University of Texas Southwestern

Medical Center in Dallas.

" The average person who is not familiar with the details of

multivariable analysis will not be in a good position to make

judgments about this study. "

Here's what to consider before you reach for another slice of cheesecake.

1. Smoking makes people leaner.

" It seems like it would be simple to figure out how weight is related

to health, " says Meir Stampfer, chair of the epidemiology department

at the Harvard School of Public Health. " But you can't just measure

height and weight and count the bodies. "

The first problem is cigarette smoking. Smokers are more likely to be

lean than overweight, and smoking raises the risk of dying of heart

disease, cancer, emphysema, and other illnesses. Since smokers make up

a sizeable proportion of lean Americans-roughly 30 percent of women in

the Nurses Health Study, for example-their higher death rate makes it

look like you're better off being overweight.

" If you don't eliminate the bias caused by smoking, it will

artificially inflate the risk of dying among the lean and

underestimate the risk of dying in the overweight, " explains JoAnn

Manson, chief of the Division of Preventive Medicine at Brigham and

Women's Hospital in Boston and professor of epidemiology at the

Harvard School of Public Health.

The controversial CDC analysis " controlled " for smoking-that is, the

researchers compared overweight to lean smokers and overweight to lean

nonsmokers.1 " Excluding smokers doesn't reduce bias; it creates bias, "

argues the CDC's on.

Manson disagrees. When she controlled for smoking-using detailed

cigarettes-per-day data, not just the CDC's smoking-or-not data-she

found that the leanest women still had a slightly higher risk of dying

(see " Factoring Out Smokers & the Sick, " p.4).

In contrast, when she looked at women who had never smoked, the

leanest women had the lowest risk of dying.2

" The effect of cigarettes on the risk of disease is so powerful and

it's so difficult to control for factors like the intensity and

duration of smoking that the only way to eliminate the bias is to look

at people who have never smoked, " says Manson.

To fend off criticism, the CDC researchers also looked at people who

had never smoked. Surprisingly, they found that overweight people

still had the lowest risk of dying.3 Perhaps that's because when the

CDC eliminated smokers, that left too few nonsmokers in the part of

the study that followed people the longest.4

The CDC data " may not be large enough to restrict an analysis to

healthy nonsmokers, " says the American Cancer Society's Thun.

2. Illness makes people leaner.

Sad to say, the leanest Americans aren't just a bunch of Lance

Armstrongs. In addition to healthy lean people and smokers, the lean

include people with cancer, emphysema, congestive heart failure, liver

disease, dementia, and other illnesses that lead to weight loss and,

eventually, death.

" It's not that being underweight causes disease, but that these

chronic diseases can cause weight loss, " explains Manson. " It's called

reverse causation. "

Most researchers exclude people who know they are sick before they

enter a study on the risk of dying. To eliminate people who don't know

that they have cancer or other diseases, most scientists exclude from

the results anyone who dies within several years after the study begins.

" To completely eliminate the biases, you have to simultaneously

eliminate current and past smokers, exclude baseline illness, and

exclude deaths within the first ten years of follow-up, " says

Hu, an associate professor of nutrition and epidemiology at the

Harvard School of Public Health. When he did that in the Nurses Health

Study of more than 115,000 women, the risk of dying was lowest in the

normal and (healthy) underweight women, and rose progressively as

women got fatter.

Factoring Out Smokers & the Sick

The new CDC study, says Willett, " took only half-hearted measures to

exclude people with chronic disease. " It didn't eliminate people who

knew they were ill. And it " excluded people who died in the first

three or five years, but that's not adequate. "

The CDC researchers couldn't exclude people who died in the first ten

years because some of the participants were only followed for nine years.

" If you have a short follow-up, you still have a problem with people

who don't know they're sick, " explains the American Cancer Society's

Thun. " As the follow-up lengthens, that's less of a problem

because the people who don't know that they're sick die. "

The CDC's on is skeptical that a longer follow-up would

matter. " I'm not convinced that following people for another decade

will make a difference, " he says. But, he adds, " as more data becomes

available, we'll certainly analyze it to see if some bias occurred

because we didn't follow up long enough. "

His concern is that if researchers exclude everyone who smokes or is

sick, so few deaths are left that the results don't apply to all

Americans.

" Other studies end up excluding 80 to 90 percent of the deaths, " he

explains. " Is the small, rarefied cohort that remains representative

of the population? "

But others counter that it's not just legitimate, but essential, to

exclude smokers and chronically ill people to figure out what weight

is healthiest.

" It really comes down to whether a study is representative or valid, "

says Thun. " You can't get a valid answer from smokers or sick people

because anyone who's ever practiced medicine knows that being sick

affects weight. We want to know about weight before, not after, people

get sick. "

Even eliminating people who die within the first ten years may not be

enough, explains Willett.

" Think of a common scenario, " he suggests. " A man who is overweight at

age 45 develops diabetes at age 50. At age 60 he has a heart attack,

and by 65 he has congestive heart failure, which causes him to lose

weight, and he dies at age 70.

" If you start looking at age 65, it looks like a lean person died, but

the death is really due to being overweight at age 45. "

Emphysema and other respiratory diseases also cloud the picture.

" Chronic respiratory insufficiency makes you very skinny, " says Thun.

" But people can survive a long time. " And that could make it appear

that being lean raises the risk of dying.

" It's always possible that being thin can raise the risk of illness, "

he acknowledges. " In fact, there's a whole literature on leanness

causing lung cancer. But I believe those studies are mistaking cause

and effect. "

When researchers exclude the sick and smokers, he adds, " almost all

the relationship between leanness and lung cancer goes away. "

3. Age often makes people leaner.

Finding a link between weight and death in older people-the group with

the highest risk of dying-is especially tricky. In part, that's

because so many older people are ill.

" People often lose weight as they get into their 70s and 80s, and it's

often due to chronic disease, " says Harvard's JoAnn Manson. " A third

to a half of people in the older age groups have at least one chronic

disease like heart disease, stroke, congestive heart failure, or cancer. "

Furthermore, researchers use body mass index-weigh\t for a given

height-to rate body fat, and BMI doesn't work so well in older people.

" BMI is a less reliable marker for fatness in the elderly because you

lose about half a pound of muscle per year as you get older, " explains

Manson. In other words, a lean 55-year-old may be muscular, while a

lean 85-year-old may be frail.

A large waist (compared to one's hips) is a better indicator of body

fat than BMI in older people, notes Manson, but people don't always

measure it accurately. " BMI is a good predictor of mortality in your

40s, 50s, and 60s, but it may not be good in your 70s and 80s. "

Rate Your Weight

What's more, adds Manson, " depletion of the susceptibles " may hide the

harm caused by obesity. " People who are susceptible to heart disease

and diabetes tend to die earlier, so if you're still obese in your

80s, you're probably relatively immune to the adverse effects of obesity. "

Unfortunately, the " chubby is good " message was music to the ears of

all ages, not just the over-80 set.

Finally, what researchers call " compression of mortality " kicks in

among older people. As you age, the risk of dying is so high that not

much influences it. " Even cigarette smoking doesn't look like a strong

predictor of mortality in your 80s and 90s, " says Manson.

That doesn't mean that health experts should advise people to gain

weight any more than they should urge people to smoke. And if the risk

of dying is already high in older people, why do anything that raises

their risk even slightly?

4. Is it plausible that obesity prevents death?

Hundreds of studies show that people who've put on extra pounds have a

higher risk of cancer, diabetes, and cardiovascular disease (heart

attacks and strokes). " Those diseases kill most people in the U.S.,

and we know that obesity contributes to all of them, " says the

University of Texas's Grundy.

Being even slightly overweight raises the risk of dying of several

cancers, according to a huge American Cancer Society study that has

tracked more than 1.2 million people since 1982.5

" The risk of dying of breast cancer increases as BMI increases, " notes

the Cancer Society's Thun. " The risk of dying of colon cancer

increases in the overweight as well as the obese. "

What's more, being overweight makes a person more likely to develop

risk factors for cardiovascular disease and diabetes, like high blood

pressure and high LDL ( " bad " ) cholesterol. " Fat tissue secretes

hormones and chemical messengers that cause insulin resistance,

diabetes, and hypertension, " says Manson.

" And we know that even modest weight loss can tremendously improve

blood pressure, diabetes, and high blood cholesterol, triglycerides,

and blood sugar levels. "

Given that " extremely strong " evidence, " is it plausible that being

overweight is protective? " she asks.

Willett puts it another way. " What yet-to-be discovered factor is so

powerful that it not only counteracts the higher risk of diabetes,

cardiovascular disease, and cancer in the overweight, but makes

overweight beneficial?

" Results like the CDC's should make researchers ask if there is some

methodological flaw or bias in their data. "

5. Healthy or merely alive?

If obesity could somehow raise the risk of disease but lower the risk

of dying, it might be a sort of bargain with the devil.

" The overweight have a significantly higher risk of diabetes,

gallstones, hypertension, and heart disease, " notes Graham Colditz,

professor of epidemiology at the Harvard School of Public Health. " All

have costs and an impact on the quality of life that get ignored if we

focus only on mortality. "

The risk of diabetes, for example, is roughly eight times higher in

overweight women-and six times higher in overweight men-than in their

lean counterparts. Obese men and women have 18 times the risk, and the

most obese have 30 to 40 times the risk.

" For nearly 20 years, we have documented the huge impact that diabetes

has on the health care system, from kidney failure to dialysis and so

on, " says Colditz.

Women who are overweight (but not obese) have a 34 percent higher risk

of dying of breast cancer than lean women. That's a fairly modest

increase-not even double-but with breast cancer striking one in eight

women over a lifetime, who needs any boost in the odds?

Two years ago, researchers at the American Cancer Society added up the

impact of both overweight and obesity on more than a dozen cancers,

including those of the colon, esophagus, kidney, and uterus.5

" We estimate that 90,000 deaths due to cancer could be prevented each

year in the United States if men and women could maintain normal

weight, " concluded the Society's Thun and others.

Obesity costs the nation an estimated $70 billion a year, says

Colditz, half of it borne by Medicare and Medicaid. " And that doesn't

include the indirect costs due to lost productivity. "

Even the CDC's on agrees. The impact of overweight is

" murky when you focus on mortality, " he says. " It gets stronger when

you focus on disease incidence. "

6. Is it now safer to be overweight?

Extra pounds may have less impact on dying than in the past, suggested

the CDC's study, because Americans are less likely to have high

cholesterol or high blood pressure or to smoke than in the past.

" There may well be a secular trend that's acting to weaken the

relationship between obesity and mortality, " says WiIliamson. " We've

undoubtedly become better at keeping people alive. "

Over the last 40 years, the percentage of people with high cholesterol

dropped more among overweight or obese than among leaner Americans,

CDC researchers reported.4 However, high blood pressure and smoking

rates dropped comparably in all weight categories.

Harvard's JoAnn Manson isn't impressed by that data. " There is very

little evidence that the effect of medical advances has been greater

on the obese than on other people, " she argues.

Researchers at the American Cancer Society compared the risk of dying

among overweight people in two of its studies-one done from 1982 to

1991 and another from 1998 to 2002. " Instead of decreasing, " said

Thun, " the relative risk of dying among the overweight actually

increased over time. "

Similarly, Harvard researchers compared data collected on nurses from

1976 to 1986 with data collected from 1990 to 2000. " There's no

evidence for a substantial decline in the impact of obesity on

mortality over time, " says Harvard's Hu.

That jibes with what experts know about treating risk factors like

high blood pressure.

" Treatment doesn't bring back the risk to that of someone without

hypertension, " notes Willett. " High blood pressure raises the risk

threefold and treatment reduces it by 25 percent. "

What's more, many people are still walking around with untreated risk

factors. " Vast numbers of people are under- or uninsured, " says Thun.

" It's not like everyone is getting state-of-the-art medical care in

this country. "

7. Commercial interests at work.

Odds are, the debate over weight will go on. The CDC is struggling

with how to estimate the risk of being overweight and how many deaths

it causes. " It's organizing a meeting to bring in the best

mathematical minds to take these issues on, " says on.

Are there other explanations to account for the discrepancies between

the CDC's studies and those by Harvard and the American Cancer

Society? For example, the CDC's study had more minorities than the

other two. Earlier studies suggest that extra pounds boost the risk of

dying less in black women than in their white counterparts.5 And

Harvard and the Cancer Society rely on self- reported weights, while

people in the CDC's study had their weights measured.

But it's not just scientific give-and-take that fuels the controversy.

Soon after the CDC study was released, the Center for Consumer

Freedom, which is funded largely by the restaurant industry, ran

full-page newspaper ads referring to the obesity epidemic as " hype. "

" Like tobacco, obesity is intertwined with the economic and social

fabric of our culture, " says the American Cancer Society's

Thun, " so it's bound to be an inflammatory and controversial topic.

But it's irresponsible for commercial interests to trivialize what has

become a major public health problem in the U.S. and globally. "

10-Year Risk of Disease

Alive... but Unhealthy

Whether or not they're more likely to die, the overweight have a

higher risk of diabetes, gallstones, high blood pressure, heart

disease, and colon cancer, according to a study that tracked 77,000

women from the Nurses Health Study.

Diabetes is the greatest threat. Obese women are 18 times more likely

than lean women to get the disease. The most obese women are 30 times

more likely (not shown).

Results are similar for the 46,000 men who were tracked as part of

Harvard's Health Professionals Study, except that extra weight raises

the risk of heart disease and stroke more in men than in women.

Industry in disguise. The Center for Consumer Freedom, funded largely

by the restaurant and food industry, used this ad to imply that the

obesity epidemic doesn't exist. Despite the small print at the top of

the ad, a recent study from the Centers for Disease Control and

Prevention may have underestimated the deaths caused by obesity

because it failed to adequately account for smoking and weight loss

caused by illness.

The Bottom Line

* As your weight increases, so does your risk of heart disease,

cancer, diabetes, and death.

* In older people, a large waist may reflect body fat better than

weight does. A large waist (at least 35 inches in women or 40 inches

in men) is a risk factor at any age.

* If you're overweight, avoid weight gain and shoot for modest weight

loss, which is usually enough to lower blood pressure and blood sugar.

* No matter what you weigh, eat a healthy diet built around

vegetables, fruit, beans, whole grains, seafood, poultry, low-fat

dairy, and modest amounts of oils, nuts, and other unsaturated fats.

* Shoot for30 to 60 minutes of exercise each day.

1 Journal of the American Medical Association 293: 1861, 1918, 2005.

2 New England Journal of Medicine 333. 677, 1995.

3 www. cdc. gov/nchs/products/pubs/pubd/hestats/ excess_deaths/

excess_deaths.htm.

4 Journal of the American Medical Association 293. 1868, 2005.

5 New England Journal of Medicine 348: 1625, 2003.

Copyright Center for Science in the Public Interest Oct 2005

Published: 2005/10/04 03:01:06 CDT

© Rednova 2004