One of the numbers that terrifies us most in this age of dieting is the Body Mass Index , which is calculated by dividing weight in kilos by the square of height in meters. It is a rough measure of the amount of fat we have in our body and based on the figure our GP will tell us if we are in the ideal zone (between 18.5 and 24.9), we are overweight (between 25 and 29.9) or, conversely, we are obese (above 30). Comparing the data from different years, we find that we have not been gaining weight at a rate of 1.5 kg per decade: in 2014, more than 640 million men and women were obese compared to 105 million in 1975.
Now, nature likes to confront us with situations that challenge our medical assumptions, and it turns out that in the same period life expectancy has jumped from 57 years in 1975 to more than 71 in 2014. As epidemiologist George Davey Smith commented from the University of Bristol, “the world is both fatter and healthier.”
For some time now, many doctors have been calling attention to the error of using BMI as a predictive factor of risk of having health problems, as studies are appearing that point in the opposite direction to what has been believed so far. Thus, a study published in August 2012 in the medical journal JAMA found that, in patients with type 2 diabetes, those who were at their normal weight were more likely to die than those who were overweight or obese. On the other hand, a meta-analysis carried out in 2013 on 97 published studies found that being overweight implied a lower risk of dying than if you had a normal BMI.
The Danish study published on May 10, which has followed more than 100,000 Copenhagen adults for 15 years, abounds in this fact: the healthiest BMI is around 27. But, be careful, this does not mean that you can eat everything you want. What it indicates is that those a little chubby should not fear for their health, as has been said with pounding insistence in recent years.
