A young study participant
exercises in a room calorimeter
as part of ARS research on
obesity in Hispanic children.
Sometimes a lack of willpower is not to blame for obesity.
Nancy F. Butte, an energy expert at the ARS
Children's Nutrition Research Center (CNRC) in Houston, Texas, is looking
at a complex of factors that may explain rising obesity in Hispanic
The CNRC, in collaboration with the Southwest Foundation
for Biomedical Research (SWFBR), is in the third year of a 5-year study
titled "¡ÁViva la Familia!" or "Long Live
the Family!" A professor of pediatrics at Baylor College of Medicine,
Butte is the study's principal researcher. Cooperating are Baylor's
Kenneth J. Ellis, professor of pediatrics; Jennifer O. Fisher, assistant
professor of pediatrics; Carlos A. Bacino, assistant professor in molecular
and human genetics; and Anthony G. Comuzzie and Shelley Cole, geneticists
at the SWFBR in San Antonio, Texas.
Childhood obesity is more prevalent among Hispanic children
than in other ethnic groups, and the U.S. problem has been steadily
increasing over the past decade. Researchers will investigate, for the
first time, the causes of childhood-onset obesity within the Hispanic
population. They hope to identify genetic and environmental factors
that make some children more prone to excess weight gain. Preliminary
results have already shown that 40 to 60 percent of the factors leading
to obesity may be genetic.
"We know that obesity is a complicated issue,"
says Butte. "A handful of susceptibility genes, yet unidentified,
are readily expressed in our current environment of plentiful food and
sedentary lifestyles. Major genes interact with the environment. This
research may lead us to a better understanding of why Hispanic children
are more obese than others."
In-depth metabolic and physiologic testing of the children
and their parents will be done in three phases at the CNRC's Metabolic
First, volunteer children and parents will be checked
for weight and height and for vital signs, such as heart rate, blood
pressure, and body temperature. Parents will give blood samples for
genetic analysis, while children go through an exercise test to measure
the amount of oxygen they use while walking on a treadmillan indicator
of physical fitness. Children and parents will have body composition
scans using dual energy X-ray absorptiometry to measure lean tissue
and body fat. Researchers will ask the children what they've eaten and
what foods and beverages they generally eat.
In the next phase, the children's energy expenditures
will be measured in a room calorimeter, which is a sealed chamber in
which their oxygen uptake and carbon dioxide output can be monitored
for 24 hours. The calorimeter is equipped with a bed, toilet, sink,
desk, radio, television, CD player, and telephone. Communication with
parents, siblings, and staff can be maintained via window, phone, and
intercom throughout the test period. A blood sample will be taken for
genetic and biochemical analyses. At the end of the 1-day tests, the
children will wear an accelerometer monitor secured on a belt to measure
their physical activity for the next 3 days.
The final phase takes place a year later, when the children's
weight, height, and body composition will once again be measured. At
this time, with the phenotypic information now in hand, connections
will be made between specific genes or genetic patterns and gain in
weight, body fat, and other factors.
The geneticists in San Antonio will perform a genomic
scan on the blood samples from the parents and children using about
360 genetic markers. Genetic statistical analysis will be performed
on the nuclear-family data to search for genes influencing obesity in
Hispanic children.By Alfredo
Flores, Agricultural Research Service Information Staff.
This research is part of Human Nutrition, an ARS National
Program (#107) described on the World Wide Web at www.nps.ars.usda.gov.
Nancy F. Butte
is with the USDA-ARS Children's
Nutrition Research Center at Baylor College of Medicine, 1100 Bates
St., Houston, TX 77030; phone (713) 798-7179, fax (713) 798-7187.
"Tracking Obesity Among Hispanic Children in the United States"
was published in the June
2003 issue of Agricultural Research magazine.