New study finds that too much or too little body mass index (BMI) can have an impact on life expectancy and be the trigger for various serious diseases.
Scientifically validated by the World Health Organization, the body mass index (BMI) makes it possible to assess an individual's corpulence according to his height and weight, regardless of his sex. Determining whether one is underweight, overweight or obese, it is also a reliable indicator of health and even life expectancy.
This is highlighted by a new study published in The Lancet Diabetes and Endocrinology and led by scientists from the London School of Hygiene and Tropical Medicine. According to its authors, people over 40 with a BMI at the top of the norm (between 22 and 25) and being in good health had a lower risk of premature morbidity.
"BMI is a key indicator of health, we know that BMI is linked to the risk of death, but surprisingly little research has been done on the links to deaths due to specific causes," says Krishnan Bhaskaran. Professor of Statistical Epidemiology and lead author of the study. "We filled this knowledge gap to help researchers, patients and physicians better understand how underweight and overweight could be associated with diseases such as cancer, respiratory disease and liver disease. . "
Cancers and cardiovascular diseases
To reach this conclusion, the researchers analyzed data from 1.7 million people and 367,512 deaths collected from British doctors. They showed that obesity (BMI 30 or higher) was linked to an increased prevalence of two leading causes of death: heart disease and cancer.
"A BMI greater than 25, the upper limit of health, is linked to most cancers, most cardiovascular diseases, respiratory diseases, and liver and kidney diseases," says Professor Bhaskaran. Underweight is also linked to "a wide range of causes of death", such as dementia, Alzheimer's disease, cardiovascular disease and suicide. However, says the epidemiologist, the links between a low BMI and causes of death are more "observational": it is indeed more difficult to know if a low weight is the direct cause of the disease or rather a marker of ill health .
Increased risk of morbidity
It also results that people who are overweight or overweight have a shorter life expectancy: 4.2 years shorter in obese men, 3.5 years shorter in obese women. And 4.3 years less for underweight men and 4.5 years for underweight women.
In particular, the results showed that the lowest risk of cardiovascular mortality was related to a BMI of 25 kg / m2, with each additional 5 kg / m2 being associated with an increased risk of morbidity of 29%. The lowest risk of cancer death was a BMI of 21 kg / m2, with each additional 5 kg / m2 associated with an increased risk of death of 13%.
However, researchers concede that there are limits to this work, including a lack of information about the diet or level of physical activity of those involved, as well as the impact that these factors may have on morbidity. .