Gene found that affects links to food intake and weight

Experts applaud new proof of the biological basis for obesity, which, according to another study, is getting worse.

By Victoria Stagg Elliott — Posted May 7, 2007

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The old chestnut that some people can eat anything without gaining a pound while others bulk up just by looking at a snack may involve both a nugget of truth and a genetic basis.

According to a study published in the February Journal of Molecular Medicine, Framingham Heart Study participants who possess the APOA5-1131C gene allele did not gain weight if they had more fat in their diet. Thirteen percent of the population carries this variation.

"We have all known people that do not watch what they eat but usually don't see any effect on their weight," said Jose Ordovas, PhD, one of the authors and director of the Nutrition and Genomics Laboratory at the Jean Mayer U.S. Dept. of Agriculture Human Nutrition Research Center on Aging at Tufts University in Boston. "This is the first study that enables us to identify this segment of the population using information on this gene."

This polymorphism previously has been implicated in increasing levels of triglycerides and stroke risk, and physicians complimented this study for demonstrating that obesity involves more than eating too much and not getting enough physical activity.

"It's one more piece of evidence that there's biology behind this, and it opens the door to new treatments down the road," said J. Michael Gonzalez-Campoy, MD, PhD, chief executive officer of the Minnesota Center for Obesity, Metabolism and Endocrinology in Eagan. He also is a Minority Affairs Consortium delegate to American Medical Association meetings and frequently has spoken on obesity-related issues.

But while several experts said this study was exciting, they also expressed caution. An increasing number of investigations are linking various genotypes to the body's response to certain food groups, but none of these connections have been confirmed by later research.

"This is a little bit of glimpse into the future and the idea of tailoring diet based on genes," said Tim Church, MD, MPH, PhD, professor at Louisiana State University's Pennington Biomedical Research Center in Baton Rouge.

"But one study doesn't mean much. This study really needs to be validated," he said. "There are a lot of articles saying how the genes interact, but nobody's replicating other people's work."

Extreme obesity rates brisk

Many believe that this kind of nutrigenomics research is the next frontier to be explored to make a dent in the obesity epidemic, which, according to a paper published online March 29 in Public Health, is getting worse.

Researchers at the RAND Corp. analyzed data from the Centers for Disease Control and Prevention's Behavioral Risk Factor Surveillance System. From 2000 to 2005, obesity, as defined as having a body mass index higher than 30, increased by 24%, but the number of people who had a BMI greater than 40 increased by 52%. The group with BMIs greater than 50 grew by 75%.

"The proportion of people at the high end of the weight scale continues to increase at a brisk rate despite increased public attention on the risks of obesity and the increased use of drastic weight-loss strategies such as bariatric surgery," said Roland Sturm, PhD, lead author and a RAND senior economist.

Previous studies also have documented the phenomenon, and the author and other experts say this increases the need for community-wide changes to make a difference.

"Everybody is getting fatter," said Caroline Apovian, MD, associate professor of medicine and pediatrics at Boston University School of Medicine. "No one's proven that it's the environment, but that's the best bet."

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Shifting weight

A recent RAND study used data from the Behavioral Risk Factor Surveillance System to examine obesity trends from 2000 to 2005. It concluded that prevalence rates for classifications that encompass the most extreme overweight categories have been growing the fastest. Among the specific findings:

  • The overall self-reported prevalence of obesity, characterized as having a BMI of more than 30, increased by 24%; but the prevalence of BMI higher than 40 -- about 100 pounds overweight -- increased by 50%, and rates of BMI higher than 50 increased 75%.
  • This finding is consistent with the public health idea that the population weight distribution is shifting, which disproportionately increases extreme weight categories.
  • Because comorbidities and resulting service use are higher among severely obese people, the widely publicized trends for overweight/obesity underestimate the consequences for population health.

Source: Public Health, March 29 (online)

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External links

"APOA5 gene variation modulates the effects of dietary fat intake on body mass index and obesity risk in the Framingham Heart Study," abstract, Journal of Molecular Medicine, February (link)

"Increases in morbid obesity in the USA: 2000-2005," abstract, Public Health, online March 29 (link)

"Assessment and Management of Adult Obesity," AMA Roadmaps for Clinical Practice series produced with support from the Robert Wood Johnson Foundation and developed in collaboration with the U.S. Dept. of Health and Human Services (link)

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