According to a new study done at the University of Bristol that analyzed BMI, mortality and health in 60,000 people including parents and their children to establish how being overweight affects risk of death, the harmfulness of being obese are underestimated. FIndings are published in the December issue of the International Journal of Epidemiology.
In the past studies suggest that it is good for health to be mildly overweight, that the risk of death appears to be above the range of optimum BMI recommended by doctors. Scientists suspect that these studies don’t reflect the true effects of BMI on health because there are other factors and behaviours that can both lower and increase risk of death, making it difficult to estimate how BMI actually affects risk of death. The purpose of this study was to investigate and assess causal links between the risk of death and BMI in a situation that was not biased by reverse causation.
The team for Bristol worked with the Norwegain University of Science and Technology using a Norwegian population based health study involving 130,000 residents. Health records of 30,000 pairs of father and children, and mother and children were examined to study the extent of which BMI may affect mortality risk. The team observed how mortality in the group of parents related to their own BMI and those of their children. Because of their BMI being related due to genetic factors, offspring BMI is an indicator of the parents BMI. Adult childrens BMI isn’t influenced by illness among parents, using offspring BMI therefore avoids problems inherent in relating BMI of parents to their risk of death. Researchers found that by using offspring BMI rather than using the parent’s BMI the harmful effects of low BMI reduced and harmful effects were greater than of those found in conventional studies. This study has results that suggests studies in the past have underestimated the harmful effects of a person being overweight.
This study supports current advice from most doctors to maintain BMI between 18.5 and 25, and the suggestion of being slightly overweight may be healthy is shown to be incorrect according to this study.
