Harmful effects of overweight are underestimated

A study from the University of Bristol has found that the harmful effects of overweight and obesity are being underestimated. The study, which contained data from around 60,000 parents and their children, analysed how obesity and BMI influences the risk of death. Previous studies have suggested the optimal BMI, at which the risk of death is minimised, is slightly above the recommended ‘normal’ range, meaning that it is good for you to be slightly overweight. However some disease courses can lead to you having a lower BMI but a higher risk of death, this makes it highly difficult to estimate how BMI actually influences risk of death.

The researchers used parent and child combinations as BMI is related due to genetic factors, however the BMI of ‘adult’ children is not influenced by illness amongst the parents, therefore using the offspring BMI avoids the problems inherent with simply relating the parent BMI to their risk of death. They found that when offspring BMI was used instead of the parent’s own BMI, the apparent harmful effects of low BMI were reduced, and the harmful effects of high BMI were greater than those found in the conventional analyses. These results therefore suggest that current studies may tend to underestimate the harmful effects of a higher BMI. The authors are therefore calling for more robust approaches for identifying causal relationships influencing health, especially the relationship of BMI to overall health.