Editor's note: We have said it already that people should not count on exercise to control their weight. Still physical activity is important.
January 05, 2009 - For Immediate Release
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PHYSICAL ACTIVITY MAY NOT BE KEY TO OBESITY EPIDEMIC, LOYOLA STUDY FINDS
MAYWOOD, Ill. -- A recent international study fails to support the
common belief that the number of calories burned in physical activity
is a key factor in rising rates of obesity.
Researchers
from Loyola University Health System and other centers compared African
American women in metropolitan Chicago with women in rural Nigeria. On
average, the Chicago women weighed 184 pounds and the Nigerian women
weighed 127 pounds.
Researchers had expected to find that
the slimmer Nigerian women would be more physically active. To their
surprise, they found no significant difference between the two groups
in the amount of calories burned during physical activity.
"Decreased
physical activity may not be the primary driver of the obesity
epidemic," said Loyola nutritionist Amy Luke, Ph.D., corresponding
author of the study in the September 2008 issue of the journal Obesity.
Luke is an associate professor in the Department of Preventive Medicine
and Epidemiology at Loyola University Chicago Stritch School of
Medicine.
Physical activity is defined as anything that
gets your body moving. U.S. government guidelines say that each week,
adults need at least 2 ½ hours of moderate aerobic activity (such as
brisk walking) or 75 minutes of vigorous activity (such as jogging).
Adults also should do muscle-strengthening activities, such as
weight-lifting or sit-ups, at least twice a week.
Physical
activity has many proven benefits. It strengthens bones and muscles,
improves mental health and mood, lowers blood pressure, improves
cholesterol levels and reduces the risk of cardiovascular disease,
diabetes, breast cancer and colon cancer.
But Loyola
research suggests that weight control might not be among the main
benefits. People burn more calories when they exercise. But they
compensate by eating more, said Richard Cooper, Ph.D., co-author of the
study and chairman of the Department of Preventive Medicine and
Epidemiology.
"We would love to say that physical activity
has a positive effect on weight control, but that does not appear to be
the case," Cooper said.
The recent study included 149
women from two rural Nigerian villages and 172 African American women
from the west side of Chicago and suburban Maywood.
Adjusted
for body size, the Chicago women burned an average of 760 calories per
day in physical activity, while the Nigerian women burned 800 calories.
This difference was not statistically significant.
Diet is
a more likely explanation than physical activity expenditure for why
Chicago women weigh more than Nigerian women, Luke said. She noted the
Nigerian diet is high in fiber and carbohydrates and low in fat and
animal protein. By contrast, the Chicago diet is 40 percent to 45
percent fat and high in processed foods.
Results of the
new study are similar to those of a 2007 study of men and women in
Jamaica. Researchers from Loyola and other centers found there was no
association between weight gain and calories burned during physical
activity.
"Evidence is beginning to accumulate that
dietary intake may be more important than energy expenditure level,"
Luke said. "Weight loss is not likely to happen without dietary
restraint."
Other centers involved in the study of Chicago
and Nigerian women include University of Ibadan in Nigeria, Howard
University, Johns Hopkins Bloomberg School of Public Health and
University of Wisconsin.
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Based
in the western suburbs of Chicago, Loyola University Health System is a
quaternary care system with a 61-acre main medical center campus, the
36-acre Gottlieb Memorial Hospital campus and 25 primary and specialty
care facilities in Cook, Will and DuPage counties. The medical center
campus is conveniently located in Maywood, 13 miles west of the Chicago
Loop and 8 miles east of Oak Brook, Ill. The heart of the medical
center campus, Loyola University Hospital, is a 570-licensed bed
facility. It houses a Level 1 Trauma Center, a Burn Center and the
Ronald McDonald® Children?s Hospital of Loyola University Medical
Center. Also on campus are the Cardinal Bernardin Cancer Center, Loyola
Outpatient Center, Center for Heart & Vascular Medicine and Loyola
Oral Health Center as well as the LUC Stritch School of Medicine, the
LUC Marcella Niehoff School of Nursing and the Loyola Center for Health
& Fitness. Loyola's Gottlieb campus in Melrose Park includes the
250-bed community hospital, the Gottlieb Health & Fitness Center
and the Marjorie G. Weinberg Cancer Care Center.
