Let's say I tell you that you have a genetic variant that makes you less capable of exercising, whether or not that is true. And then, you get on a treadmill.
Or I tell you that you have a genetic variant that helps maintain a healthy weight, whether or not that is true. And then you eat a meal.
An experiment set up along these lines -- with a more complex design to allow for hypothesis testing -- revealed that just knowing about your genetic make-up can affect how your body responds. It's a bit head-spinning.
"Receiving genetic information doesn't just make you more informed," said Stanford psychologist Alia Crum, PhD, in a Stanford News article. "What this study shows is that it can also have a physiological impact on your body in a way that actually changes your overall risk profile."
The research appears in Nature Human Behavior.
First, researchers collected DNA samples from the 200-plus study participants. Then, half of them had a meal, while the other half performed an exercise test. After the meal, researchers measured molecules in the blood that signal satiety -- a cue to stop eating which is protective against obesity.
When the participants returned a week later, they were told the results from the genetic tests, with a twist. Some were told that they were at risk for obesity, when they actually weren't, while others were told they had a lower capacity for exercise, when they actually didn't.
Then, on to the meal, and the treadmill. Here's where the findings get curious, because researchers were able to compare each participant's performance after they knew (or thought they knew) about their genes, with their baseline condition.
From the release:
What the researchers found is that the information alone changed how people performed.
Those who were told they had a version of the gene that made them less prone to obesity actually performed better after the second meal. They produced two and a half times more of the fullness hormone, even though the meal was identical to the one they'd eaten the week before...
People who were told they were genetically prone to obesity saw little or no change in how full they felt or in their hormone levels.
By contrast, people told they had a gene that made them respond poorly to exercise then went on to do much worse on a challenging treadmill test. Their lung capacity was reduced, they were less efficient at removing carbon dioxide, and they quit the treadmill test sooner...
People told they had the protective gene variant performed about the same as in the first test.
This means that genetic counselors, physicians and others need to be particularly careful about how they deliver genetic results, researchers say.
"The take-home message here is that the mindset that you put people in when you deliver genetic risk information is not irrelevant," Crum said. "The mindset of being genetically at risk or protected can alter how we feel, what we do and -- as this study shows -- how our bodies respond."
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