People always be curious to know the mystery of duration of human life will be glad to know that one of such criterion has been revealed by the scientists from Harvard University and Tufts University in the US. In their study, it has been found that those who have been lean all their lives are likely to live longer, while those with a heavy body shape from childhood up to middle age have the highest mortality risk.
Researchers tracked the evolution of body shape and associated mortality among two large cohort studies. Their study included more than 100K participants, out of which 80,266 were females and 36,622 were males. These participants recalled their body shape at ages 5, 10, 20, 30, and 40 years. They also provided body mass index at age 50 and were followed from age 60 over a median of 15-16 years for death. In addition, they have been asked several questions on medical information and lifestyle every two years, and on diet every four years.
After analysing the recorded data, it showed that people who remained lean throughout life had the lowest mortality, with a 15-year risk of death being 11.8 percent of females, and 20.3 percent of males. While, those who reported being heavy as children and who remained heavy or gained further weight, especially during middle age, had the highest mortality, with a 15-year risk of death being 19.7 percent of females and 24.1 percent of males.
In a separate study, researchers claim that increasing levels of body mass index (BMI) are associated with higher risks of premature death. The BMI is an established way of measuring body fat from the weight and height of a person, but the optimal BMI associated with the lowest mortality risk is not known.
It is expected that a higher BMI is associated with a reduced life expectancy, but the largest previous study showed that when compared with normal weight, overweight was associated with reduced mortality, and only high levels obesity were associated with increased mortality.
However, there were various limitations in the study, for example, smoking and prevalent or prediagnostic illness were not taken into account, both of which can lead to lower body weight, and increased mortality. So researchers in the current study sought to clarify this association by carrying out a large meta-analysis of 230 prospective studies with more than 3.74 million deaths among more than 30.3 million participants.
They analysed people who never smoked to rule out the effects of smoking, and the lowest mortality was observed in the BMI range 23-24 among this group. Lowest mortality was found in the BMI range 22-23 among healthy never smokers, excluding people with prevalent diseases. Among people who never smoked, and studied over a longer duration of follow-up of more than 20 and 25 years, where the influence of prediagnostic weight loss would be less, the lowest mortality was observed in the BMI range 20-22.
The research was published in the journal BMJ.