In an early 19th-century best seller, a
famous food writer offered a cure for obesity and chronic
disease: a low-carbohydrate diet.
The notion that what you eat shapes your medical fate
has exerted a strong pull throughout history. And its
appeal continues to this day, medical historians and researchers
"It's one of the great principles no, more than principles,
canons of American culture to suggest that what you eat
affects your health," says James Morone, a professor of
political science at Brown University.
"It's this idea that you control your own destiny and
that it's never too late to reinvent yourself," he said.
"Vice gets punished and virtue gets rewarded. If you eat
or drink or inhale the wrong things you get sick. If not,
you get healthy."
That very American canon, he and others say, may in part
explain the criticism and disbelief that last week greeted
a report that a low-fat diet might not prevent breast
cancer, colon cancer or heart disease, after all.
The report, from a huge federal study called the Women's
Health Initiative, raises important questions about how
much even the most highly motivated people can change
their eating habits and whether the relatively small changes
that they can make really have a substantial effect on
The study, of nearly 49,000 women who were randomly assigned
to follow a low-fat diet or not, found that the diet did
not make a significant difference in development of the
two cancers or heart disease. But there were limitations
to the findings: the women assigned to the low-fat diet,
despite extensive and expensive counseling, never reached
their goal of eating 20 percent fat in the first year
only 31 percent of them got their dietary fat that low.
And the study did not examine the effects of different
types of fat a fact that critics say is a weakness at
a time when doctors are advising heart patients to reduce
saturated fat in the diet, not overall fats.
The researchers also found a slight suggestion that low
fat might make a difference in breast cancer but the results
were not statistically significant, meaning they may have
occurred by chance.
Still the study's results frustrate our primal urge to
control our destinies by controlling what we put in our
mouths. And when it comes to this urge, it is remarkable
how history repeats itself. Over and over again, medical
experts and self-styled medical experts have insisted
that one diet or another can prevent disease, cure chronic
illness and ensure health and longevity. And woe unto
those who ignore such dietary precepts.
For example, Jean Anthelme Brillat-Savarin, the French
19th-century food writer, insisted that the secret to
good health was to avoid carbohydrates. Brillat-Savarin,
a lawyer, also knew the response his advice would provoke.
" 'Oh Heavens!' all you readers of both sexes will cry
out, 'oh Heavens above!" he wrote in his 1825 book, "The
Physiology of Taste." "But what a wretch the Professor
is! Here in a single word he forbids us everything we
must love, those little white rolls from Limet, and Achard's
cakes and those cookies, and a hundred things made with
flour and butter, with flour and sugar, with flour and
sugar and eggs!"
Brillat-Savarin continued, "He doesn't even leave us
potatoes or macaroni! Who would have thought this of a
lover of good food who seemed so pleasant?
" 'What's this I hear?' I exclaim, putting on my severest
face, which I do perhaps once a year. 'Very well then;
eat! Get fat! Become ugly and thick, and asthmatic, finally
die in your own melted grease."
The Frenchman's recipe for good health was only one of
many to come. A decade later, the Rev. Sylvester Graham
exhorted Americans to eat simple foods like grains and
vegetables and to drink water.
Beef and pork, salt and pepper, spices, tea and coffee,
alcohol, he advised, all lead to gluttony. Bread should
be unleavened, and made with bran to avoid the problem
of yeast, which turns sugar into alcohol, he continued.
It is also important, he said, to seek out fresh organic
fruits and vegetables, grown in soil without fertilizers.
The reward for living right, Graham promised, would be
A few decades later came Horace Fletcher, a wealthy American
businessman who invented his diet in 1889. He was 40 and
in despair: he was fat, his health was failing, he was
always tired and he had indigestion. He felt, he said,
like "a thing fit but to be thrown on the scrap-heap."
But Fletcher found a method that, he wrote, saved his
life: eat only when you are hungry; eat only those foods
that your appetite is craving; stop when you are no longer
hungry and, the dictum for which he was most famous, chew
every morsel of food until there is no more taste to be
extracted from it.
Fletcher became known as the Great Masticator, and his
followers recited and followed his instructions to chew
their food 100 times a minute. Liquids, too, had to be
chewed, he insisted. He promised that "Fletcherizing,"
as it became known, would turn "a pitiable glutton into
an intelligent epicurean."
Along with the endless chewing, Fletcher and his supporters
also advocated a low-protein diet as a means to health
But by 1919, when Fletcher, 68, died of a heart attack,
his diet plan was on its way out, supplanted by the next
new thing: counting calories. Its champions were two Yale
professors, Irving Fisher and Eugene Lyman Fisk, who wrote
the best-selling book "How to Live."
"Constant vigilance is necessary, yet it is worthwhile
when one considers the inconvenience as well as the menace
of obesity," Fisher and Fisk advised their readers.
More recently, of course, the preferred diet, at least
for cancer prevention, has been to eat foods low in fat.
And that was what led to the Women's Health Initiative,
a study financed by the National Institutes of Health
comparing low fat to regular diets.
Eight years later, the women who reduced dietary fat
had the same rates of colon cancer, breast cancer and
heart disease as those whose diets were unchanged.
They also weighed about the same and had no difference
in diabetes rates, or in levels of insulin or blood sugar.
It made sense to try the low-fat diet for cancer prevention,
said Dr. Elizabeth Nabel, the director of the Women's
"In the mid- to late 1980's, there was a body of literature
that was suggestive that diet might impact the incidence
of breast cancer and colorectal cancer," Dr. Nabel said.
For example, studies found that women acquired a higher
risk of those cancers if they moved to the United States
from countries where incidence of the cancers was low
and where diets were low in fat.
And there were animal studies indicating that a high-fat
diet could lead to more mammary cancer.
But intriguing as those observations were, there was
no direct, rigorous evidence that a low-fat diet was protective.
The Women's Health Initiative study would be the first
rigorous test to see if it was. The study investigators
decided to follow heart disease rates, as well.
"Think of it," said Dr. Joan McGowan, an osteoporosis
expert who is also a project officer for the Women's Health
Initiative. "Here was a hypothesis that just a better
diet could prevent breast cancer. How attractive was that?"
In the meantime, the notion that fat was bad and that
low-fat diets could protect against disease took hold,
with scientists promoting it and much of the public believing
it. And a low-fat food industry grew apace.
In 2005, according to the NPD Group, which tracks food
trends, 75 percent of Americans said they substituted
a low-fat or no-fat food for a higher-fat one once a week
So last week, when the study's results, published in
The Journal of the American Medical Association, showed
that the low-fat diets had no effect, the study investigators
braced themselves for attacks.
Dr. Jacques Rossouw, the project officer for the Women's
Health Initiative, said the researchers knew that some
critics would say the women did not reduce the fat in
their diets nearly enough. Perhaps a lower-fat diet would
have offered some protection against cancer, Dr. Rossouw
said. But, he said, "what we achieved is probably what
Other critics said that the study made a mistake in even
aiming for 20 percent of calories as fat. Dietary fat
should be even lower, they said, as low as 10 percent.
But Dr. Rossouw said this was unrealistic, because try
as they might, people are not able to change their eating
habits that much.
"You can't do that," he said. "Forget it. It's impossible."
Critics now are telling the investigators that the study
was useless because it focused on total fat in the diet,
rather than on saturated fat, which raises cholesterol
levels. If the women had focused instead on getting rid
of fats like butter, had substituted fats like olive oil
and had eaten more fruits and grains, then the study might
have shown that the proper diet reduces heart disease
risk, they claim.
"Lifestyle goes beyond a modest difference in saturated
fat," said Dr. Robert H. Eckel, president of the American
Dr. Rossouw responded, "They're telling us that we chose
the wrong kind of fat and that we just didn't know."
But, he said: "We're not stupid. We knew all that stuff."
The investigators, he said, had long debates about whether
to ask the women to reduce total fat or just saturated
In the end, they decided to go with total fat because
the study was primarily a cancer study and the cancer
data were for total fat.
If the women had reduced just their saturated fat, their
dietary fat content would probably have been even higher,
fueling the critics. And, he said, some animal data indicate
that polyunsaturated fat may even increase cancer risk.
"We looked at all possible scenarios," Dr. Rossouw said.
But, he said, given the study's disappointing findings,
he was not surprised by the critics' responses.
Not everyone is attacking the study. Many scientists
applaud its findings and say it is about time that some
cherished dietary notions are put to a rigorous test.
And some nonscientists are shocked by the reactions of
the study's critics.
"Whatever is happening to evidence-based treatment?"
Dr. Arthur Yeager, a retired dentist in Edison, N.J.,
wrote in an e-mail message. "When the facts contravene
conventional wisdom, go with the anecdotes?"
The problem, some medical scientists said, is that many
people researchers included get so wedded to their beliefs
about diet and disease that they will not accept rigorous
evidence that contradicts it.
"Now it's almost a political sort of thing," said Dr.
Jules Hirsch, physician in chief emeritus at Rockefeller
University. "We're all supposed to be lean and eat certain
And so the notion of a healthful diet, he said, has become
more than just a question for scientific inquiry.
"It is woven into cultural notions of ourselves and our
behavior," he said. "This is the burden you get going
into a discussion, and this is why we get so shocked by
The truth, said Dr. David Altshuler, an endocrinologist
and geneticist at Massachusetts General Hospital, is that
while the Western diet and lifestyle are clearly important
risk factors for chronic disease, tweaking diet in one
way or another a bit less fat or a few more vegetables
may not, based on studies like the Women's Health Initiative,
have major effects on health. "We should limit strong
advice to where randomized trials have proven a benefit
of lifestyle modification," Dr. Altshuler wrote in an
Still, he said, he understands the appeal of dietary
The promise of achieving better health through diet can
be so alluring that even scientists and statisticians
who know all about clinical trial data say they sometimes
find themselves suspending disbelief when it comes to
diet and disease.
"I fall for it, too," says Brad Efron, a Stanford statistician.
"I really don't believe in the low-fat thing, but I find
myself doing it anyway."