With two thirds of Americans either overweight or obese — weight loss remains a major struggle for millions.

Now it turns out there may be a genetic reason for that — what some are lightly calling the ‘couch potato gene’.

Ariella Jackson has a love-hate relationship with exercise.

“I don’t want to get up. I don’t want to exercise,” said Jackson.

But when she stopped training she gained weight.

The twenty-one year old blames herself.

But a new study indicates it could be another culprit.

The gene FTO, already linked to obesity risk, is now linked to something else, the will to exercise.

“So the robot is pulling DNA from this plate.”

For a decade, geneticist Molly Bray has isolated millions of DNA samples from thousands of subjects.

“When people tell you, ‘exercise is hard, it hurts for me,’ they’re not lazy, they’re reporting to you exactly what they’re feeling,” said Dr. Bray.

In their DNA, she found the person with one FTO sequence is more likely to keep exercising with the other FTO sequence is more likely to drop out.

During final trials at UAB, subjects are asked to train for fifteen weeks and are measured, tested and interviewed.

“The hardest part was just actually deciding to do it.”

Doctor Bray said that is FTO talking. It worked for Shane Day.

“I couldn’t run a solid mile, couldn’t run a solid quarter mile. Now, I can run six miles,” said Day.

Proof you can fight and conquer your own genes.

Scientists said the study is an important step in identifying causes for obesity in humans — and will also help physicians be more understanding of overweight patients.

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