[acb-diabetics] genotype depends on weight loss

Tue Apr 6 21:21:03 GMT 2010

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Researchers are cautious, of course, but the latest study showed that when
individuals were assigned to different diets -- including the
low-carbohydrate

Atkins diet and low-fat Ornish diet -- based on their genotype, they lost
significantly more weight than those assigned to a diet unsuited to their
genetics.

Dr. Christopher Gardner (Stanford University) writes, "Say you and your wife
went on the Atkins diet, and you both think you followed it religiously, but

you lost 13 pounds and she lost nothing and is angry because she followed
the same diet. Well, she might have a different genotype. She isn't
genetically

predisposed to do well on a low-carbohydrate Atkins diet."

The new data are derived from a study the group previously conducted in 311
overweight women who were randomized to four popular diets: the
very-low-carbohydrate

Atkins diet, the low-carbohydrate Zone diet, the very-low-fat Ornish diet,
and the low-fat LEARN diet. In that trial, known as the
Atkins-Traditional-Ornish-Zone

(A TO Z) study, women assigned to the Atkins diet had a modest benefit
relative to the other diets, but overall results were disappointing in that
the

women, on average, lost only about 10 pounds.

"Within every diet group, though, some of the women lost more than 30 pounds
and kept it off for over a year," said Gardner. "And some of the women
gained

more than 10 pounds. Within every diet, the range is at least 40 to 50
pounds. Between the different diets, the weight loss difference was just a
few pounds,

yet within the group, the difference is much larger. This is actually much
more interesting than the difference between groups. How can the responses
to

the same diet be so different?"

With these data, the researchers were approached by Interleukin Genetics
(Waltham, MA), asking them if they could obtain the DNA of the study
participants.

The company had previously identified three genes -- ABP2, ADRB2, and
PPAR-gamma -- that could predict weight loss. These genes were shown to
predict weight

loss in three different studies, were biologically plausible, and were shown
to have gene-diet interaction, said Gardner.

The researchers obtained DNA from 138 women and analyzed the weight loss
according to genotype and diet in 133 participants. Among those participants
who

completed the 12-month study, researchers observed a significant interaction
between diet assignment and weight loss after taking genotype pattern into

consideration.

Women assigned to a genotype-appropriate diet lost 5.3% of their body weight
compared with just 2.3% among those not matched to genotype (p=0.005).
Within

the Atkins group, for example, those appropriately assigned by genotype lost
approximately 12 pounds compared with 2 pounds for those who lacked the
low-carbohydrate

genotype. In the Ornish group, similar reductions in weight were observed
among those appropriately assigned by genotype. 

Gardner said the proportion of individuals who were genetically predisposed
to the low-fat or low-carbohydrate diets is roughly 50-50, so a significant

number of people will fall into each category. He stressed, however, that
all individuals assigned to the diet groups were instructed to make healthy,

wholesome food choices.

"If they were on low-carbohydrate and high-fat, they weren't told to eat
butter and whipped cream but to eat nuts, seeds, and fatty fish," he said.
"If

they were on the low-fat diet, they weren't told to just eat low-fat
Snackwell cookies but to eat veggies, whole grains, and beans. I get worried
when

people just say low-carbohydrate or low-fat because they don't really
understand what that means. This is what really undermines the whole
public-health

low-fat message."

Dr. Lawrence J. Appel (Johns Hopkins University, Baltimore, MD) said there
is interest in the genetic underpinnings of nutrition, however, the
environment

is key in reducing obesity worldwide. "This is an area of burgeoning
interest," said Appel, "but the obesity epidemic occurred pretty quickly,
over the

past 10 or 20 years, and our genetic pool did not change in the same period.
Our obesity epidemic is an environmental problem. Given the environment,
genes

might influence the response to the environment, but are the genes causal?
No. It's likely that the environment has a dominant impact."

Gardner agrees, that the genetic predisposition to do well on certain diets,
but not on others, will not put an end to the obesity epidemic, but that the

findings could be helpful in fighting the battle of the bulge. The results
are retrospective and need to be interpreted cautiously, but his group is
planning

to conduct a larger prospective study that assigns individuals to the
different diets based on genotype.

"The results don't explain the whole nutrition puzzle, but it explains a
large enough chunk to be of interest," he said.

Nelson MD, Prabhakar P, Kondragunta V, et al. Genotype patterns predict
weight loss success: The right diet does matter. Presented at EPI|PNAM
(Cardiovascular

Disease Epidemiology and Prevention and Nutrition, Physical Activity, and
Metabolism) Conference March 2-5, 2010. 

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