 | |||||||||||||||
 |
|
 | |||||||||||||
 | |||||||||||||||
 |
 |
||||
|
Current issue
Carbohydrates on trial
A study just launched at The Rockefeller University Hospital will
determine whether high fat diets truly work better than high carb diets
BY JOSEPH BONNER
When the Atkins diet first became a national
obsession about two years ago, millions of Americans became carb
counters. One American, Rockefeller’s Jan L. Breslow,
had a different reaction.
After reading a July 2002 New York Times Magazine
cover story on the diet, Breslow began digging
through medical literature, looking for evidence that the latest
diet craze would work any better than any other low-calorie diet.
“I found that there’s hardly any good, carefully
controlled data out there,” says Breslow, Frederick Henry
Leonhardt Professor and head of the Laboratory of Biochemical
Genetics and Metabolism at Rockefeller.
That won’t be the case for long. Breslow
will soon enroll his first volunteer in a rigorous study designed
to determine which of two low-calorie diets — one high in
fat, the other high in carbohydrates — best reduces abdominal fat in
overweight and obese people. Subjects who volunteer for the study
will lose, on average, 20 pounds, and scientists will gain a better
understanding of the effects of these diets on body composition,
risk factors for heart disease and stroke, and overall health.
The Atkins craze has led huge numbers of
Americans — Dr.
Atkins’ New Diet Revolution has
sold over 15 million copies — to abandon low-fat, high-carb
diets, which are the basis of the food pyramid recommended by the
U.S. Department of Agriculture, the American Heart Association, the
American Cancer Society and many other health organizations, in
favor of high fat diets. The author of the New York Times Magazine
article, science writer Gary Taubes, agreed with
cardiologist Robert C. Atkins, the late inventor of the diet, that
carbohydrates — rice, grains, pasta and sugars
— and not fat are responsible for obesity.
To find out if that’s true, Breslow and
Research Nurse Practitioner Jill Culiner of The Rockefeller
University Hospital will enroll 50 obese or overweight subjects
over the next five years, with the expectation that 40 of them will
complete the protocol. Subjects will live overnight at the hospital
for 16 weeks and will eat precise meals prepared by the
hospital’s bionutritionists Janet Maturi and Diane Meehan.
For the first three weeks of the study, they
will eat an average American diet — containing approximately
34 percent fat — to determine the average number of calories
they need to maintain their then-current weight. They will spend
the next 10 weeks on either a high fat or a high carbohydrate diet.
Both diets will represent a 40 percent calorie reduction in order
to induce weight loss. In the final three weeks, the subjects will
continue on the diets, but calories will be added as needed to
maintain their new weights.
The study will be the first to comprehensively
record a person’s changes in body composition and
cardiovascular risk factors over the entire course of a diet, from
weight stabilization through loss and maintenance of new weight.
Each subject’s weight and blood pressure will be checked
daily. Periodic measurements will be made of several blood
components, including insulin, glucose, lipoproteins, which
transport cholesterol in the blood, and leptin, the “obesity
hormone” discovered 10 years ago by Rockefeller’s
Jeffrey Friedman. Body composition before, during and after weight
loss will be measured by magnetic resonance imaging at the Obesity
Center at St. Luke’s Hospital by Steve Heymsfield and Stanley
Heschka.
“Most of the other inpatient diet
studies in the literature are shorter, and only a few measurements
are taken, usually when people are starving,” Breslow says.
Recently, two outpatient studies published in
the journal Annals of
Internal Medicine provided
evidence that the low carbohydrate Atkins diet is more effective
than a low fat diet during a six-month period, although the
weight-loss results even out for both diets over the course of a
year.
“The focus of the two new studies and
many others in the literature is outpatient adherence to the two
diets,” says Breslow. “This involves many complex
behavioral issues and is epitomized by the question ‘What do
you do at 11 p.m. when standing in front of the
refrigerator?’”
Although behavioral aspects of dieting are
important, Breslow explains, behavioral studies depend on many
factors, such as education, physician follow up, availability of
certain foods, family situation and economic status, among others.
“To adequately address these issues would require a totally
different study design than we have pursued and is really not our
expertise,” says Breslow. “The Rockefeller Hospital
excels in carefully monitored metabolic studies.” (See
“Precision nutrition,” right.)
Breslow is primarily interested in evaluating
how much visceral fat each patient loses during the course of the
study. Visceral fat, which accumulates around the organs in the
abdomen, is much more strongly associated with insulin resistance,
diabetes, heart disease and stroke, hypertension and gout than
total body fat or subcutaneous fat.
The study also should help answer some myths
regarding high fat diets. For example, it’s commonly
accepted, without any scientific evidence, that the low blood levels of insulin that
accompany a high fat, low carbohydrate diet have special metabolic
effects that promote weight loss. “But the truth is, we
really don’t know,” says Breslow. “It’s
never been studied.”
Because each study participant can expect to
lose about two pounds a week on either diet, for a total loss of 20
pounds by the end of the inpatient period, Breslow calls it a
therapeutic study. “The subjects can view their participation
as a good start toward maintaining a healthy weight,” says
Culiner. “They will learn what good portion sizes are and
how to eat healthfully. And because the meals are based on natural
foods, they will learn the best kinds of food to eat.”
Precision nutrition
Why The Rockefeller University Hospital is uniquely
qualified to conduct dietary studies
BY BETSY HANSON
Jan L. Breslow isn’t the first Rockefeller
scientist to take on obesity. The Rockefeller University Hospital has been
famous since the 1950s for research that requires special diets to study
metabolism or nutrients.
They’ve gotten quite good at it.
“This type of protocol — studying a small
number of people with tightly controlled variables — is the
hospital’s forte,” says Breslow.
While other research hospitals are weighed down with
the beaurocracies associated with routine patient care, Rockefeller is free
to focus on research studies initiated by scientists.
The bionutrition department, for example, will be
critical to Breslow’s research. Instead of preparing thousands of
daily meals for patients with diverse needs, as might be the case
elsewhere, Rockefeller’s bionutrition team will devote its resources
to making precise, personalized meals for just a few patients at a time. A
staff of 11 will produce 24 different meals for three diets. Each portion
of every food — bacon for a high fat, high protein diet, spaghetti
for a high-carb diet, etc. — will be weighed to one-tenth of a gram
before it is packaged. The patients will receive customized, color-coded
servings based on their specific calorie requirements.
Though this is work the hospital staff have been doing
for half a century, this study’s five-year timeframe presented a
particular challenge. Because the nutrient content of fruits and vegetables
can vary widely depending on where they were grown and when they were
harvested, the staff will purchase large quantities of food, then measure
and freeze individual portions. In this way, the scientists can be sure
that the first volunteers to enroll in the study eat exactly the same foods
as the last ones.
The country’s only free-standing research
hospital outside of the National Institutes of Health, The Rockefeller
University Hospital this year completed its first major modernization in
decades. Upgraded laboratory and patient care facilities, strengthened
support services and new initiatives to ensure high quality care and high
quality science have made the hospital one of the nation’s premier
facilities for conducting clinical research.
July 16, 2004 |
|
|
||
|
Archive: 2005 2004 2003 2001-2002 1999-2000 | ||||
