The body mass index (BMI) has for a long time been the standard measurement used to determine whether someone’s weight is ‘healthy’ or not. BMIs (calculated by dividing weight in kg by the square of someone’s height in metres) of 25 or more are generally regarded as ‘unhealthy’. The suggestion is there are somehow mortal dangers from having a BMI in this range. However, good hard measures of health (like risk of death) show that individuals who are labeled ‘overweight’ according to the BMI enjoy at least as good health, if not better, than those traditionally labeled as ‘healthy’ (e.g. a BMI of 18.5-24.9). For more about the science which shows this see here.
The largest body of evidence regarding the non-hazards of being overweight (cited in the article linked to above) come from the USA. Do they translate to other parts of the World? In a study published recently in the International Journal of Epidemiology the association between BMI and overall risk of death was assessed in a group of almost 76,000 individuals from a rural Indian population (Kerala state, South India). These individuals were monitored over nearly a decade. Here are the results for men, using a body mass index of 18.5-22.9 as a reference point:
BMI >16: risk of mortality increase of 26 per cent
BMI 16-18.4: no statistically significant relationship with risk of death
BMI 23.0-24.9: no statistically significant relationship with risk of death
BMI 25-27.4: no statistically significant relationship with risk of death
BMI >27.5: no statistically significant relationship with risk of death
Results for women were similar.
Low body weight is associated with an increased risk of death. But, here again, it seems that being ‘overweight’ does not put individuals at heightened risk of death.
Better measures of health status and risk of death appear to be waist circumference and the waist-to-hip ratio. For more about this, see here.
Sauvaget C, et al. Body mass index, weight change and mortality risk in a prospective study in India. Int. J. Epidemiol. 2008 37: 990-1004