Over the last 30 years, obesity has become a growing epidemic in the U.S. Currently one-third of all adults and nearly 20 percent of kids in the U.S. between the ages of 12 and 19 meet the qualifications for obesity, according to the Centers of Disease Control and Prevention. While the number of obese Americans remains high, the possibility exists that these numbers could swell even more as 67 percent of the country qualifies as either overweight or obese.
America had ranked as the heaviest nation in the world until a UN report released in early July found that Mexico had slightly overtaken the U.S. in percentage of the population that qualifies as obese.
While Americans’ notoriously sedentary lifestyles and poor dietary habits have contributed greatly to the country’s growing weight problem, a new study suggests weight gain may have just as much to do with people’s genes as it does their diet.
A new study has uncovered a potential genetic explanation for why some overeat and have a higher risk of obesity. According to a committee of international researchers, individuals who carry multiple copies of the gene “FTO” have a higher tendency to feel hungry more quickly following a meal, as their bodies carry higher levels of the hormone ghrelin, which creates feelings of hunger in the body.
Further more, brain scans of study participants revealed that individuals with twice the typical number of FTO genes experience a different reaction in the brain to ghrelin and food. Individuals with the double variant of the gene demonstrated different neural responses in the region of the brain known to control appetite and the reward/pleasure center that typically becomes stimulated following the use of alcohol or drugs.
Approximately one out of every six people carries the FTO gene variant. These individuals have a 70 percent greater chance of becoming obese when compared to those who don’t carry both variants of the gene.
The results of this study where published in the Journal of Clinical Investigation.
Genetics’ Role in Weigh Gain
Researchers have known for some time that FTO gene variations possess a strong link to obesity, it was only until recently they began to gain a better understanding of why. The results of this latest study indicate to researchers with two copies of the FTO gene have a biological predisposition to eat more.
Researchers believe that evolution plays a primary role in why so many people carry two variants of the FTO gene today.
For the majority of human history, food was a scare resource. Researchers suspect that individuals who had the double FTO gene would have possessed a unique advantage that helped promote survival. Experiencing hunger pangs more frequently would of led early humans to hunt and gather more frequently, thus increasing the likelihood they would always have enough to eat.
To determine the role FTO plays in weight gain, researchers asked a group of men- half with the double variant and half with a version of the FTO gene that has links to lowering the risk of obesity- to rate how hungry they felt both before and following a meal. Participants also had blood samples taken so researchers could test ghrelin levels.
While blood levels of ghrelin usually increase before a meal and decrease after eating, researchers found that men who possessed the double FTO variant had much higher levels of ghrelin in their blood following a meal and reported being hungry more quickly following a meal than participants who possessed the FTO variant that carries a decreased risk of obesity.
Using a different group of male participants, researchers then used MRI technology to measure how the brain reacts to images of food and the levels of ghrelin in the bloodstream before a meal. The scans showed different brain activity in the men with the double FTO variant, both in the regions of the brain that control appetite and those that act as the pleasure/reward center of the brain. This altered brain activity was in response to images of food and to the amount of ghrelin in the bloodstream.
Researchers also found that men with the double FTP variant also rated images of high calorie foods more highly following a meal when compared to participants with the low-risk FTO variant.
While researchers are excited about what the results of this latest study, they are quick to caution that genes are not the sole cause of weight gain. Obese individuals who carry the FTO gene are on average only 6 1/2 pounds heavier than those without. So while genetics certainly seem to play a role in whether an individual carries a predisposition to overeat, additional factors still play a role.
Despite this limitation, research of this nature can better enable doctors to identify individuals predisposed to obesity at an early age, and develop treatment methods designed to deal with genetic dispositions to overeat.
Timothy Lemke is a freelance health and science writer. To read more of his work, visit the website of Dr. Mick Brooks, a dentist in Tumwater, WA.