In a recent study from UCL, researchers find that compared to BMI, waist-to-hip ratio may be a better index of health issues like stroke and heart disease.
Previously there have been many studies that have found links between obesity and the risk of coronary heart diseases, stroke and type 2 diabetes.
However, these results can be misleading because association does not equal causation, and lifestyle factors, such as smoking and weight loss, may not have been considered.
In addition, other studies have shown consistent links between both BMI and waist-to-hip ratio to both chronic heart disease and ischemic stroke.
A similar association has also been shown between measures of obesity and type 2 diabetes.
In these studies, it is virtually impossible to separate the effects of BMI and waist-to-hip ratio from each other because they are so closely linked.
In the study, the researchers looked at multiple genetic variants linked to BMI and waist-to-hip ratio adjusted for BMI, as a measure of obesity and central body fat in up to 229,000 people.
They found a clear causal relationship between increased BMI and central body fat (measured by waist-to-hip ratio) with higher risks of coronary heart disease and type 2 diabetes.
The finding also suggests that central body fat may have a stronger effect on stroke risk than BMI.
But both measurements should be used when estimating the impact of fat distribution on health.
The researchers believe that this large-scale genetic study is the most comprehensive study about the causal relation between obesity and cardiovascular disease to date.
The team suggest that while BMI is a successful indicator of risk for some diseases, waist-to-hip ratio may be a better indicator of risk for other diseases, especially stroke.
While it is difficult to disentangle the two measures, waist-to-hip ratio should be considered as another valuable marker of risk.
The finding also suggests that doctors should pay attention to measures of obesity beyond BMI, because these measures may offer additional information to help find patients at risk of heart disease and stroke.
The finding is published in Circulation.
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