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The secret of your risk of obesity can be partially blocked in your genes at birth.
At present, a team of researchers from the Broad Institute of MIT and Harvard, Mbadachusetts General Hospital and Harvard Medical School has developed a "polygenic score" based on genomic screening to quantify this future risk. obesity.
Scientists badyzed 2.1 million sections of the human genome related to body weight ("polygenic" literally means "a lot of genes") and badyzed this by means of a newly developed computer algorithm.
They first validated and then tested against the weight data of 119,000 people and 288,000 people, respectively.
The researchers found that people who were at risk of genetic obesity among the top 10% of markers were 25 times more likely to be severely obese than those with less than 10% obesity. .
This represented a difference of almost 30 pounds on average.
People in this high-risk group also had a higher risk of coronary heart disease by 28%, a higher risk of diabetes by 72%, a risk of high blood pressure of 38% and an increased risk of heart disease. heart failure 34%.
So, are we ready to discover the risk of obesity of our children through a blood test?
Not quite, say the authors of the study.
"A high polygenic score does not necessarily mean that someone is doomed to become obese," said Dr. Sekar Kathiresan, co-author of the study and director of the Cardiovascular Disease Initiative Broad Institute and Professor of Medicine at Harvard Medical School. in a press release.
"DNA is not destiny. We know that a healthy lifestyle can compensate for a genetic predisposition, even if those with a high genetic risk will probably have to work much harder to maintain a normal weight, "he said.
In other words, this polygenic notation clarifies and improves the idea that the risk of obesity is partly genetic and not simply a matter of will.
This could also offer opportunities for early intervention.
"Since the weight trajectories of individuals … begin to diverge in early childhood, such interventions may have maximum effect when they are used early in life," the researchers write in their study.
Some researchers are more critical of the current limitations of genetic testing and their utility to the general public.
"Obesity is partly genetic, partly due to lifestyle. Heritability is about 50%, Ruthline Loos, PhD, director of the Genetics Program for Obesity and Related Metabolic Features at Mount Sinai Hospital in New York, told Healthline. .
"But the other 50% is due to the fact that people have different lifestyles, different diets, different levels of physical activity, etc.," she added. "So, if you have a genetic score – and even if it was a perfect genetic score – you still capture only half of people's genetic susceptibility.You still can not accurately predict future obesity, because you do not capture the lifestyle. "
As for this study, she says, the score is far from perfect or predictive.
She points out that among the top 10% of the highest polygenic scores in the study, 58 out of 371 developed severe obesity.
There were still 313 who did not do it.
Similarly, there were 166 people in the middle of the 80% who developed obesity, although they did not have the greatest number of risk factors.
"So you can ask yourself if it's ethical to scare people who are not actually developing obesity?" She said.
The researchers themselves note that this polygenic scoring system is an improvement over other models that account for far fewer genetic variants in their paper, but they said it was far from complete.
If they envision a future where this polygenic notation is useful for badessing the risk of several diseases, they call for a careful study of the most remote people "who maintain a normal weight despite an adverse score or develop severe obesity despite a favorable score ".
Instead, they hope that this research will "provide a clear understanding of the genetic predisposition to obesity [that] can help de-stigmatize obesity in patients, their health care providers and the general public. "
"We are just beginning to identify the best way to inform and help patients overcome the health risks badociated with their genetic history," said Dr. Amit V. Khera, lead author of the Study, clinician and member of the Mbadachusetts Research Faculty. Genomic Medicine Center of the General Hospital, said in the press release. "We are extremely excited about the potential for improved health outcomes."
For the moment, better predictors of future obesity may already exist.
Loos says that his own calculations revealed that family history is still a better predictor of future obesity than genetic tests – even if they are imperfect.
This is because family history tells about a person's genetics, their environment, and their culture. That's both sides of the coin.
"Family history captures the genes, but also the lifestyle, the family environment and the way you raise your children, which has a huge impact on future risks," she said. "Also the socio-economic environment. Individuals with less money [have] less money to spend on natural foods. "
The advantage of early prediction is that it could be more powerful than discovering your genetic risk markers in adulthood.
"Obesity is very different from cancer," she said. "It's a bit in the future. You feel somehow in control (with other diseases) because this is not yet the case. With obesity, at the age of 20 or 30, you are usually there or not. "
Whether it's a genetic score or a family badessment, the question remains: what can be done to prevent obesity if they fall into a high-risk group?
This is the individual aspect: try to eat healthy, exercise and maintain adequate daily caloric intake.
Then there is the structural side, which may require a more comprehensive approach.
That, Loos says, is harder to understand.
"We need societal measures," she said. "We need a food industry that truly seeks to get people to eat healthy foods, to offer healthy products at the right price."
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