Genes May Make Some People More Motivated To Overeat [SUNY]

=== Incomplete Teaser/Summary ==========

The reinforcing value of food, which may be influenced by dopamine
genotypes, appeared to be a significantly stronger predictor of
consumption than self-reported liking of the favorite food. What's more,
obese participants clearly found food to be more reinforcing than
non-obese participants. The authors conclude that, "Food is a powerful
reinforcer that can be as reinforcing as drugs of abuse."

Both obesity and the genotype associated with fewer dopamine D2
receptors predicted a significantly stronger response to food's
reinforcing power. Perhaps not surprisingly, participants with that high
level of food reinforcement consumed more calories.

The results also revealed a three-rung ladder of consumption, with
people who don't find food that reinforcing, regardless of genotype, on
the lowest rung. On the middle rung are people high in food
reinforcement without the A1 allele. Atop the ladder are people high in
food reinforcement with the allele, a potent combination that may put
them at higher risk for obesity.

[A big word way of saying "Your Mileage May Vary.. for these reasons"]

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Source: American Psychological Association
Date: October 15, 2007

Genes May Make Some People More Motivated To Eat, Perhaps Overeat

Science Daily — Science has found one likely contributor to the way that
some folks eat to live and others live to eat. Researchers at the
University at Buffalo, The State University of New York, have found that
people with genetically lower dopamine, a neurotransmitter that helps
make behaviors and substances more rewarding, find food to be more
reinforcing than people without that genotype. In short, they are more
motivated to eat and they eat more.


The findings appear in Behavioral Neuroscience. Insights into genes and
eating could inspire custom-tailored treatment programs for obesity,
perhaps including genetically targeted drugs.

Led by Leonard Epstein, PhD, a distinguished professor of pediatrics and
social and preventive medicine at the university's medical school, the
team brought 29 obese adults and 45 adults who were not obese into the
lab for a controlled study of the relationships among genotype,
motivation to eat and caloric consumption.

Epstein's team was particularly interested in the influence of the Taq1
A1 allele, a genetic variation linked to a lower number of dopamine D2
receptors and carried by about half the population (most of which
carries one A1 and one A2; carriers of two A1 alleles are rare). The
other half of the population carries two copies of A2, which by
fostering more dopamine D2 receptors may make it easier to experience
reward. People with fewer receptors need to consume more of a rewarding
substance (such as drugs or food) to get that same effect.

Epstein differentiates reinforcing value, defined by how hard someone
will work for food, from the "feel good" pleasure people get from food,
saying, "They often go together, but are not the same thing."

Researchers measured participants' body mass, swabbed DNA samples from
inside their cheeks, and had them fill out eating questionnaires. There
were two behavioral tasks.

In the first task, participants rated various foods -- from chips to
candy bars -- for taste and personal preference. This apparent
preference test disguised a task that measured how much participants ate
when food was freely available.

In the second task, participants could swivel between two computer
stations. Pressing specified keys on one earned points to eat their
favorite food; pressing keys on the other earned points to read a newspaper.

The resulting behavioral measures included calories consumed as energy
in kilocalories, reflecting both amount and caloric density, and time
spent earning food instead of the opportunity to read the news.

Both obesity and the genotype associated with fewer dopamine D2
receptors predicted a significantly stronger response to food's
reinforcing power. Perhaps not surprisingly, participants with that high
level of food reinforcement consumed more calories.

The results also revealed a three-rung ladder of consumption, with
people who don't find food that reinforcing, regardless of genotype, on
the lowest rung. On the middle rung are people high in food
reinforcement without the A1 allele. Atop the ladder are people high in
food reinforcement with the allele, a potent combination that may put
them at higher risk for obesity.

The reinforcing value of food, which may be influenced by dopamine
genotypes, appeared to be a significantly stronger predictor of
consumption than self-reported liking of the favorite food. What's more,
obese participants clearly found food to be more reinforcing than
non-obese participants. The authors conclude that, "Food is a powerful
reinforcer that can be as reinforcing as drugs of abuse."

Researchers still view reinforcement as one of several factors that
motivate eating behavior, but the present study highlights the genetic
contribution and role of reinforcement. In theory, people producing less
dopamine may, as a result, require more food to reach a certain state of
reward or reinforcement that might be reached quicker, after less
consumption, by those with a different genotype.

Findings such as these can help obesity experts to pinpoint people at
greater risk for obesity and to develop treatments tailored to specific
risk factors. "Behavior and biology interact and influence each other,"
says Epstein. "The genotype does not cause obesity; it is one of many
factors that may contribute to it. I think the factors that make up
eating behavior are in part genetic and in part learning history."

He and his colleagues speculate that, as with other public-health
campaigns, it may be better to focus behavior change efforts on those at
high risk. "A strategy for someone who is high in food reinforcement
would be very different from the strategy for someone who is low in food
reinforcement but higher in activity reinforcement," they wrote. Using
overweight men, the group has already found that chemically manipulating
dopamine levels alters eating behavior, a finding highly suggestive for
pharmaceutical intervention.

Note: Dr. Leonard Epstein is also a consultant to Kraft Foods.

Article: "Food Reinforcement, the Dopamine D2 Receptor Genotype, and
Energy Intake in Obese and Nonobese Humans"; Leonard H. Epstein, PhD,
Jennifer L. Temple, PhD, Brad. J. Neaderhiser, PhD, Robbert J. Salis,
MD, Richard W. Erbe, MD, and John J. Leddy, MD, University at Buffalo,
The State University of New York; Behavioral Neuroscience, Vol. 121, No. 5.

Note: This story has been adapted from material provided by American
Psychological Association.