Rat Study Helps Us Understand Why Some People Have An Easier Time Getting Fit


It’s springtime, which means hoards of people are rushing off to the gym in an effort to get fit for swimsuit season and other skin-baring activities in the sunshine. They do their workouts side by side, exerting themselves to a similar degree, and while the sweat equity may be the same, some will reap the rewards of flat tummies, endurance, and muscles while others will see no improvement at all. The disparity between what type of individual gets fit faster and why has been broadly explained by genetics and what has been classified as the "obesity gene."

One such study examining the DNA samples of 84 women found that the participants with genes that predisposed them to obesity actually gained weight after following an exercise program. As explained in LiveScience, the researchers grouped the women based on their genetic risk to obesity and found that...

…women whose genes put them at a high risk of obesity gained an average of 2.6 lbs. (1.2 kilograms) during the study period, whereas women whose genes put them at a low risk of obesity lost 2.9 lbs. (1.3 kg), on average.”

We’d like to think that we all have an equal shot at getting in shape. Still, when you join the gym with your best friend who quickly becomes fit as a fiddle while you lag behind it begs the question, what gives!?

That was the query behind a recent rodent study that aimed to dig even deeper into the question of why some people don’t seem to respond to exercise the same way as others. The research, published in The Journal of the American College of Cardiology was a joint effort between scientists from the University of Michigan in Ann Arbor and the Norwegian University of Science and Technology in Trondheim.

Be prepared for some bad news that will bring out the fatalist in you. However, this information could have a bright side when we learn more about what exercise works best for different body types.

The study began with the notion that some rats were more responsive to cardio fitness training than others. Scientists observed which male rats responded best to running exercises and bred them with females of similar abilities. They also bred the male and female rats that showed little improvement together as well. These high and low achievers were meant to create multiple generations. The idea being that they would potentially follow in their forebearer’s footsteps when it came to how they responded to exercise.

Interestingly enough it worked! Seven generations later, the rats were set on itty-bitty treadmills and observed for improvement. The ones that had the been bred to respond to exercise increased the distance they were able to run by 40 percent compared to their weakling counterparts who actually lost 2 percent of their endurance during the training.

This certainly seemed to prove a prominent biological disposition to fitness but the scientist weren’t finished. Next, they set about measuring the pitter-patter of the little rat hearts during the cardiovascular exercise routines on the treadmill. What they found was quite surprising. While the size (strength) of the left ventricle usually increases during exercise in both animals and human hearts, this was not the case for the weaker set of rats.

This suggests that the reason the animals actually lost a degree of fitness while training had to do with a cellular intractability: what strengthens most hearts, seems to sap the bodies of others.

An article in The New York Times goes on to explain,

When they carefully assessed gene expression in the animal’s heart cells, they found more than 360 genes that were operating differently in the two groups of animals. Many of these genes are known to affect cell growth.”

In other words, the genes that work to increase the size and strength of the heart were not functioning effectively for the rats bred to resist exercise—a stark reality for those of us that struggle in vain to get fit. But remember: some fitness is always better than none, so you might as well compare yourself to no one but the great person you see in the mirror. And soon we may have ways to tailor exercise better to various genetic predispositions (i.e. ride a bike vs. run, free weights vs. machines, etc.).


Read all articles by Juniper Briggs 

Leave a comment

Your email address will not be published
Please check your e-mail for a link to activate your account.
Join Now Become a Member Donate

Most Shared

tag "story" with "home_most_shared"