Your Waistline,Great Aunt Agnes and Mice. What Do They Have In Common?

Pointing Fingers

People are quick to blame their weight problems on Grandma Betty, Great Aunt Agnes, and Uncle Bob.  The latest research shows that genetics do play a role in overweight and obesity, but there’s a lot more to it than that.


“You can’t help it, honey. You’re built just like me.” Flickr photo by Ines Njes

That Darn Research Project

Boston Children’s Hospital, home to the world’s largest research enterprise, has identified a genetic cause of obesity.  Through research, the children’s hospital team have discovered that mice with a genetic mutation in the Mrap2 gene gained weight while eating the same amount of food as their normal non-mutated gene counterparts. Humans have a similar gene, MRAP2 that plays a role in regulating metabolism and food consumption.

Here’s how it works in mice.  Proteins created by Mrap2 send a signal to the brain which increases metabolism and decreases appetite.  This signal is part of a larger chain of events involved in energy regulation.

Mutations in this chain increase the likelihood of obesity.  In fact, the mice that had their Mrap2 gene knocked out as part of research project grew to about twice their normal size. Researchers made some other interesting discoveries too:

  • Weight gain was more pronounced in the male mice
  • Mice without the Mrap2 gene incurred even greater weight gain when fed a high fat diet.
  • The Mrap2 negative mice didn’t eat more at first, but still gained weight.
  • They continued to gain weight even though they were eating the same foods in the same quantity as the other mice.
  • The mice without the Mrap2 gene had to be under-fed 10 to 15 percent to gain weight at the same rate as their counterparts.
  • As soon as they were taken off of a restricted diet they gained weight.

The evidence is pretty compelling and can help us to understand how a similar chain of events can take place in humans with similar results.  It looks like we may even be able to blame our family members for our battle of the bulge.

Not So Fast

The Boston researchers did a follow-up study on obese humans and found four mutations in the MRAP2 gene.  They believe that these mutations, when present, have a direct impact on obesity.  They concluded, however, that these rare mutations are responsible for obesity in less than one percent of the population.

Further studies on obesity-related genes have been done using a genome-wide association that scans hundreds of thousands of genetic markers across thousands of individual’s sets of DNA to find variations. They found obesity-related gene variants to be fairly common have determined that they impact between 20 and 30 percent of the population, putting them at a higher risk of obesity.

These preliminary studies hold insight as to how the body manages energy storage and could help with future treatments for obesity. But gene mutations are not responsible for the rising incidence of overweight and obesity in our society.  In fact, subsequent studies on gene mutations and their relationship to obesity found that lifestyle factors, such as being physically active, and consuming lower-calorie nutritious whole foods can counteract the gene-related risk.

It’s Not Entirely Aunt Agnes’ Fault

We may want to blame our mom, great-uncle or cousin twice-removed for giving us a gene that makes it hard for us to control our weight, but researchers agree that genetics play a minimal role. More than likely what we’ve inherited from our relatives is a love for high-calorie ethnic foods, recipes for rich, fattening holiday dishes, cravings for sodium and sugar and an adoption of sedentary past times and hobbies.

Bad news?  Not at all. Really it’s good news because it doesn’t allow us to make excuses for our behaviors or blame a distant family member for our plight.  It puts the onus on us and confirms that when we make positive choices and take the steps necessary to change our behaviors we can achieve and maintain a healthy weight.

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