How obesity affects life expectancy: a study
'06.02.2021'
Source: Naked Science
The study found that people with normal weight in early adulthood have the lowest risk of premature death, and over the years they can gradually gain weight, but not bring the situation to obesity, writes Naked Science.
It is no secret that obesity leads to cardiovascular diseases, the development of diabetes, disorders of the musculoskeletal system, provokes the risk of cancer and is fraught with many other problems. According to the World Health Organization, a few years ago, about 13% of the world's adult population (11% of men and 15% of women) were obese - its prevalence in the world is growing steadily every year.
But it is worth distinguishing between obesity and overweight: the first is set when the body mass index (BMI, the ratio of weight in kilograms to the square of height in meters) exceeds 30, and the second - when the indicator is greater than or equal to 25. However, the authors of a new study are in a hurry to reassure those who is prone to overweight: according to their findings, people who enter adulthood with a normal BMI, and at a later age gain weight, but do not bring the situation to obesity, tend to live the longest. And those who acquired obesity at an early age and continue to exacerbate the situation throughout their lives were at the greatest risk of premature death.
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“The effect of weight gain on mortality is complex. It depends on both the time and the degree of weight gain, as well as the baseline BMI. <...> Our message is that those who at 31 years old have a normal body weight, but moderately gain weight throughout life and become obese at a later age, in fact, can increase their chances of survival ", - noted Hui Zheng of Ohio State University, lead author of the study published in the Annals of Epidemiology.
Scientists came to such conclusions after analyzing data from 4576 adults who participated in the Framingham Heart Study from 1948 to 2010, and 3753 of their descendants (they were followed from 1971 to 2014). Most of the people (3913) in the original cohort had died by the end of the study - this way you can find out how BMI developed during their adult life, and get a more accurate estimate than previous work that looked at the relationship between obesity and mortality.
After reviewing data on how participants' body mass index changed over the years, the researchers found that the older generation tended to follow one of seven BMI trajectories throughout their lives. In the younger generation, six trajectories were identified: for example, there was no group that would lose weight throughout the entire time.
After accounting for the many factors that influence the risk of premature death, such as smoking, gender, education, marital status and chronic illness, the authors calculated how each BMI trajectory is associated with mortality.
"Among the original cohort, people who were of normal weight at age 31 and gradually became overweight during middle age or later had the lowest risk of death - even compared to those who maintained normal weight throughout adulthood." - write scientists.
Further, those who were consistently overweight without hesitation claimed a higher life expectancy; they were followed by people whose BMI was on the very border between normal weight and thinness. Less "lucky" for those who started with obesity, but then lost weight, as well as gaining weight to obesity of the first, second and third degrees.
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Although both generations showed the same basic results, the researchers reported some disturbing trends in younger participants.
“Trajectories with higher BMIs in the younger generation tend to shift upward at an earlier age compared to their parents. Although the mortality risk associated with obesity has dropped from generation to generation, its contribution to mortality in the population increased from 5,4% in the original cohort to 6,4% in offspring. This is because in the younger cohort, more people immediately followed the “obesity trajectory,” "Zheng concluded.
