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After decades of research showing the incredibly close connection between obesity and heart problems, a Swedish study has finally proven what we have long suspected: overweight does not do it. cause cardiac disease.
Obesity alone – without other risk factors such as high cholesterol, inactivity, and diabetes – increases the risk of heart disease in a person by almost a third, as does the risk of heart disease. have shown previous research.
Finally, researchers at the Karolinska Institute used a method called Mendelian randomization that proves that a high BMI is a direct cause of heart disease.
And so, a third of the world's population – the proportion of overweight or obese humans – could be on the way to becoming the leading cause of death, with no lifestyle changes or medical intervention.
Finally, a Swedish study has finally shown that the link between obesity or excess weight and cardiovascular disease is causal.
The first study of this type was based on hundreds of thousands of Britons and a revolutionary statistical technique called Mendelian randomization.
This allowed the Swedish team to use genetic variants to show the cause-and-effect relationship between cardiovascular disease and BMI (body mass index).
In particular, they discovered that BMI and body fat increased, as did the risk of presenting more than half a dozen conditions, especially aortic stenosis.
It is there that the valve controlling the blood flow from the heart to the largest blood vessel of the body, the aorta, narrows and fails to open it completely.
If nothing is done, it can lead to serious problems or even death.
Professor Susanna Larsson, of the Karolinska Institute in Stockholm, said: "The association of cause and effect between BMI and fat mass and several diseases of the heart and blood vessels, especially the stenosis of the aortic valve, was unknown.
"Using Mendelian randomization, we found that a higher BMI and fat mass are associated with an increased risk of stenosis of the aortic valve and most other cardiovascular diseases, suggesting that excess body fat is a cause of cardiovascular disease. "
The theory of "fat but fit" suggests that a bulging waistline is not harmful as long as other metabolic factors such as blood pressure and blood glucose are within recommended limits.
But more and more evidence shows that this is wrong – it may be that an erroneous message is sent to millions of people.
Using data from 367,703 men and women aged 40 to 69, they identified 96 gene mutations related to BMI and body fat to estimate their effect on 14 cardiovascular diseases.
Participants came from the British Biobank, which contains biomedical information on half a million people. They were all British and were between 40 and 69 years old.
Those with variants predicting a high BMI had an increased risk of aortic valve stenosis – as well as many other life-threatening conditions.
These included heart failure, deep vein thrombosis, hypertension, peripheral artery disease, coronary artery disease, atrial fibrillation and pulmonary embolism.
For each estimated increase in BMI from a genetic point of view, the increased risk ranged from 6% for pulmonary embolism to 13% for aortic valve stenosis.
Above a BMI deemed "healthy" (20-25), this corresponds to a weight gain of about six and a half pounds (nearly three pounds) for a person measuring 5 feet 7 inches.
The study, published in the European Heart Journal, also revealed that the risk of cardiovascular disease increased in parallel with predictive mutations in the increase in body fat.
Again, the link with aortic stenosis was most pronounced – with an increased risk of 46%.
The damaged valve means that less blood leaves the heart and that the heart has to redouble its efforts to pump enough blood to circulate in the body.
The blood can go up in other parts of the heart and sometimes in the lungs. This can lead to shortness of breath, fatigue, fainting, chest pain and irregular heartbeats.
Then come strokes, atrial fibrillation, heart failure, peripheral artery disease, deep vein thromboses, high blood pressure and coronary heart disease.
These genetic variants can all predispose people to gain weight, the researchers said.
But they pointed out that the most important factors involved in the development of cardiovascular disease are diet and physical activity.
Professor Larsson said, "Our genes can make us a little more prone to weight gain, but lifestyle factors, such as overeating and lack of physical activity, are the main determinants of overweight. .
"A healthy diet is the cornerstone of cardiovascular disease prevention, and we need to limit our intake to the amount of energy needed to maintain a healthy weight," from 18.5 to 24.9.
"People who are predisposed to higher BMI may need to work harder to maintain a healthy weight." Mendelian randomization uses mutations known to be associated with potential risk factors, such as BMI and body fat, as "indirect" or "proxy" indicators.
This allows researchers to determine if the risk factor is the cause of the disease, not the opposite.
It also reduces the bias in the results because the variants are determined during the design and can not be affected by subsequent external or environmental factors, nor by the development of a disease.
Two years ago, scientists who were conducting a study of 3.5 million Britons over 20 years by the University of Birmingham found that those who were obese but showed no initial sign of heart disease, diabetes or High cholesterol levels were not protected later.
Last year, a study conducted by the University of Glasgow among 300,000 Britons of middle age revealed that the risk of contracting an illness, such as a heart attack or an accident cerebrovascular, increased by each measure all the more than it was big.
The findings go against previous studies that say that being overweight is not necessarily a sign of poor health.
Having a BMI of 25 to 29.9 is considered overweight, and 30 or more obese
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