PHILADELPHIA, Jun 25, 2001 (PRNewswire via COMTEX) -- New evidence that
overweight plays a pivotal role in causing type 2 diabetes, plus insights on the
role of the brain and of exercise in maintaining weight loss, was reported here
today at the American Diabetes Association's 61st Annual Scientific Sessions.
"The vast majority of type 2 diabetes might be prevented by adopting a more
healthy lifestyle, which would also likely be beneficial in preventing the
cardiovascular disease that often occurs as a complication of diabetes," said
Frank B. Hu, M.D., Ph.D., assistant professor of nutrition at Harvard University
School of Public Health, reporting on the Nurses Health Study in a recent
interview.
Other speakers at the meeting reported that:
* those trying to improve their diets often don't seem to "know" what they
are really eating;
* overeating may stem from parts of the brain involved in other addictive
behaviors;
* the key component of long-term maintenance of successful weight loss may
rest more with exercise rather than reduced food intake -- and a higher
level of physical activity than previously believed.
Approximately 16 million Americans have diabetes, a group of serious diseases
characterized by high blood sugar levels that result from defects in the body's
ability to produce and/or use insulin. Diabetes can lead to severely
debilitating or fatal complications, such as blindness, kidney disease, heart
disease and amputations. It is the sixth leading cause of death by disease in
the U.S.
OVERWEIGHT AS CULPRIT
The Nurses Health Study has followed nearly 85,000 women for 16 years,
monitoring their diet, exercise levels, smoking, and alcoholic consumption.
Those considered at low risk for diabetes had a body mass index (a measurement
of obesity) under 25; performed moderate to vigorous physical activity for at
least a half hour daily; were not smokers, ate a healthful diet high in cereal
fiber and polyunsaturted fat and low in transfat and glycemic load; and consumed
an average of at least a half a drink of an alcoholic beverage daily.
An evaluation of the 3,300 new cases of type 2 diabetes that have developed
showed that overweight and obesity were the single most important predictors of
diabetes. "Indeed, 90% of cases were associated with lack of adherence to the
low-risk pattern, and a majority of the cases involved overweight or obesity,"
reported Dr. Hu.
DO WE KNOW WHAT WE EAT?
A North Carolina study documented a common problem among dieters that impairs
the ability to study obesity: people's failure to accurately report what they
have eaten. This does not seem to be intentional lying but rather an inability
to "know" what they were eating that arises from multiple psychosocial
mechanisms.
A sample of 200 African American women with type 2 diabetes, average age 59,
were enrolled in a one-year dietary and exercise intervention, which included
private and group sessions and telephone-follow-up. However, at baseline, each
was randomly called three times over the course of a month and asked to report
everything she had eaten over the prior 24 hours.
"For 92% of our participants, the self-reported caloric intake was well below
that needed to maintain their basal functions, based on their height, weight and
age," reported Carmen D. Samuel-Hodge, Ph.D., R.D., Project Director of A New
Dawn (a church-based diabetes intervention), in a recent interview. Clearly,
what we are able to pull from our memory for a 24-hour food recall is a complex
issue, and she offered several possible explanations.
"If you want to see yourself as someone following a diet, recalling otherwise is
inconsistent with what you believe yourself to be," explained Dr. Samuel-Hodge.
"Another part of the problem may be issues related to trying to please the
interviewer by reporting what they think they should be eating."
"Further, most people are not good on a dietary recall process. We tend to
remember the scheduled meals where we sat down to eat and forget what we did not
plan to eat -- the snack eaten walking down the street or the bun eaten on the
job," said Dr. Hodge. "If you eat with intention, you remember. But people eat
for many reasons other than nutrition, such as to relieve stress or be social."
The greater the level of obesity, the greater was the likelihood of under-
reporting of caloric intake in this group of women. In the literature, across
all ethnic groups, the four characteristics of people most likely to under
report caloric intake are: being female, older, of lower socioeconomic status,
and obese. The authors conclude that an improved dietary assessment methodology
is needed to better identify actual food intake and better evaluate dietary
interventions.
MOTIVATION VS. METABOLISM IN FOOD INTAKE
Why we eat will be discussed at the meeting tomorrow, in a symposium on Neural
Regulation of Food Intake, by Charles Billington, M.D., president of the North
American Association for the Study of Obesity. In a recent interview, he
discussed the differences of opinion in this area. "While I and many others
consider the brain the most important organ in determining whether an individual
will have a weight problem, the role of brain function remains controversial,"
he explained.
The "metabolic" school focuses on recent discoveries highlighting the role of
hormones and brain chemicals in signaling the brain about fat and energy
storage. Some researchers believe that disorders in these hormones or chemicals
are likely the cause of most obesity. However, Dr. Billington points out that
"It's hard to explain the average national increase in American body weight in
the past 20 years, with more than 15% now obese, by saying that everyone's
metabolic sensing mechanisms suddenly went to sleep."
The "motivation" school focuses on research relating problems in weight
regulation to brain mechanisms similar to those implicated in other rewarded
behavior, such as drug and alcohol abuse, that may be responding to the food
temptation the American lifestyle places in front of us and the brain mechanisms
that reinforce those temptations.
These 'motivation'-related mechanisms take place in a totally different part of
the brain from the metabolism-related mechanisms involving hormones. However,
Dr. Billington believes there is a network involving many brain sites in which
the wiring travels back and forth between the motivation and metabolism areas.
The net result of that processing influences the outcome, which is eating.
"This view helps us better understand what has happened in America, which has to
do with the desirability of foods," said Dr. Billington. "We are asking the
learning/thinking part of the brain to overcome temptations that occur at a more
basic part of the brain. So it's not just an issue of willpower."
NEED FOR EXERCISE EMPHASIZED
But what we do with the calories we eat -- how we burn them off -- was presented
by Mary Lou Klem, Ph.D., assistant professor of psychiatry, University of
Pittsburgh School of Medicine, in a "Meet the Professor" session report on the
National Weight Control Registry.
"The Registry is an observational study, now ongoing for eight years, of people
who have lost at least 30 pounds and have kept it off for a year or more," she
explained in a recent interview. Of the 3,200 people enrolled, the average loss
has been about 70 lbs. On average, enrollees have maintained a minimum of 30
lbs. of their loss for about six years. These successful weight losers
originally reduced their weight by a wide range of means -- standard diets,
commercial programs, etc. But they all seem to be maintaining their loss in the
same way, such as by watching portion size, and limiting calorie and fat intake.
"However, what makes them stand out is their very high degree of physical
activity, burning about 2700 calories weekly, in various programs that would
amount to about one to one and one-half hours of walking daily" she reported.
"It takes real dedication to keep that up long-term." She noted that, in
standard weight loss programs, people are encouraged to burn 1500 calories per
week, while these successful lifestyle-modifiers are doing nearly double that
amount of exercise.
"The take-home message is that we see a glimpse of hope," said Dr. Klem. "In
contrast to the general public perception that it's impossible to keep weight
off permanently, this group shows that it can be done but may require even
higher levels of exercise than is generally recommended."
The American Diabetes Association is the nation's leading voluntary health
organization supporting diabetes research, information and advocacy. Founded in
1940, the Association has offices in every region of the country, providing
services to more than 800 communities.
