Physical Activity May Not Be Key To Obesity Epidemic
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.
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.
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.
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 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.
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.
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.
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
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.
recent study included 149 women from two rural Nigerian villages and
172 African American women from the west side of Chicago and suburban
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.
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
45percent fat and high in processed foods.
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
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."
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.
For more information on Loyola University Health System, visit http://loyolamedicine.org.