WIN Wyoming and WIN the Rockies
Genetic/Environment Interactions and Obesity
How much of our body weight is determined by genetics, and how much is
determined by our environment? The International Society for Behavioral
Nutrition and Physical Activity (ISBNPA) wrestled with the answer to that
question at its annual convention this summer in Quebec, Canada. The society
gathered together some of the leading researchers on the subject and asked them
to share some of their findings. For this monthís thought bullets, I share a
few of the highlights of those findings with you.
- Luigi Bouchard presented the results from the Genome-Wide Analysis of
Eating Behaviors in the Quebec Family Study. He stated, "We now
have good evidence that differences in eating between normal weight and
obese subjects are not only explained by environmental and cultural factors,
but also by genetic factors." The group of researchers tried to
identify genes influencing eating behaviors by using a genome scanning
analysis procedure. The procedure allowed researchers to identify five
chromosomal regions linked to disinhibition with eating and susceptibility
to hunger. The scan analysis did not uncover any evidence of a genetic
linkage to restraint and eating. Although the exact genes influencing eating
behaviors have not yet been identified, researchers stated the findings from
this study show promise for understanding the exact genetic mechanisms that
influence the regulation of food intake.
- Claude Bouchard also presented at the conference. Bouchard is the Director
of the Pennington Biomedical Research Center at Louisiana State University.
He has helped to write over 500 papers on the genetic and molecular basis of
obesity, including the genetic influence on physical activity. Bouchard told
conference participants the influence of environment and genetics on body
weight would be easy to study if both occurred separately. Unfortunately,
they occur simultaneously. The interactions of genetic and environment
factors produce widely varying findings in research. Highlights from
Bouchardís presentation included the following:
- A gene has been identified in the fruit fly that determines if the fly
is a "rover" or a "sitter."
- Results from the HERITAGE Family Study demonstrated a wide
variety in the maximal oxygen uptake (VO2max)
response to physical activity training. The responses aggregated by
families, indicating a genetic component for the measurement.
- A third presenter at the conference was Angelo Tremblay. Tremblay is on
the faculty of Medicine at the University Laval in Quebec City, Canada.
During his presentation, Tremblay pointed out the genotypes in populations
have not changed significantly over the last few centuries. Lifestyles have
changed significantly, even within the last few decades. Tremblay defined
obesity as the "genetically-determined susceptibility to environmental
factors." A recent study conducted by Tremblay found adolescent girls
who had a certain genotype at baseline, were significantly more likely to
have increased subcutaneous adiposity over a 12-year follow-up period when
compared to the girls who did not have that genotype. Adjusting for factors
such as dietary fat consumption, alcohol consumption and physical activity
did not influence the results. Stress-related factors did impact the
results. These findings led Tremblay to hypothesize that energy uptake of
food may be a result of an interaction of genotype with environmental
factors, with the genetic/environmental interaction being influenced by
Source: International Society for Behavioral Nutrition and Physical Activity,
ISBNPA newsletter, Volume 2, Issue 1, October 15, 2003.
Compiled by Betty Holmes, MS, RD
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