'BMI, waist circumference, and waist-to-hip ratio, whether assessed singly or in combination, do not importantly improve cardiovascular disease risk prediction in people in developed countries when additional information is available for systolic blood pressure, history of diabetes, and lipids' say the researchers from Emerging Risk Factors Collaboration Coordinating Centre, University of Cambridge, UK.
BMI (Body Mass Index) is a measurement of body fat based on height and weight that applies to both men and women between the ages of 18 to 65 years. BMI can be used to indicate if you are overweight, obese, underweight or normal. A healthy BMI score is between 20 and 25. A score below 20 indicates that you may be underweight; a value above 25 indicates that you may be overweight or obese. It's only a rough indicator of the weight and fat mass status.
On the other hand, waist-to-hip ratio is used to assess risk for heart disease and hypertension specifically. Research indicates that waist-to-hip ratio is even better for determining risk of heart problems than body mass index.
People who have a high BMI and a waist size of more than 40 inches (35 inches in women), are at a higher risk for obesity-related health problems such as diabetes, high blood pressure and heart disease.
Apple-shaped obesity and pear-shaped obesity are two types of obesity. People who are apple-shaped carry the bulk around their waist, while those who are pear-shaped carry their weight in the hip or thighs.
Previous studies had suggested that people with apple-shaped obesity were at a much higher risk for heart disease than "pear-shaped" ones. A ratio higher than 0.09 becomes a risk factor for men and above 0.85 is a risk factor for women. The risk increases with the ratio. Recent studies have refuted those findings, so a large international consortium of scientists set out to settle this issue.
This study, funded by the British Heart Foundation and UK Medical Research Council and published in The Lancet, aimed to analyze individual data from 221 934 participants in 58 prospective studies to produce reliable estimates of associations of BMI, waist circumference, and waist-to-hip ratio with first-onset cardiovascular disease outcomes.
The results from the analysis of individual data from 221 934 people without initial cardiovascular disease have shown that BMI, waist circumference, or waist-to-hip ratio, assessed singly or in combination, do not importantly improve prediction of cardiovascular disease risk when additional information is available on blood pressure, history of diabetes, and cholesterol measures
Findings of previous smaller studies and WHO guidelines have suggested that for situations in which no information is available on lipids for cardiovascular disease risk prediction (such as in resource-limited settings), assessment of simple adiposity measures can be used instead.
However, development of lipid assessment in resource-poor settings is a must as the study indicates that a combination of BMI and waist-to-hip ratio provides only about a quarter of the extra predictive information provided by total and HDL cholesterol.'Our findings reliably refute previous recommendations to adopt baseline waist-to-hip ratio instead of BMI as the principal clinical measure of adiposity,' say the investigators. Some studies suggest that waist-to-hip ratio is three times more strongly related to myocardial infarction than BMI. But this study clearly states that BMI, waist circumference, and waist-to-hip ratio each have a similar strength of association with cardiovascular disease risk.
Measures of abdominal adiposity, such as waist circumference and waist-to-hip ratio especially in combination with high triglyceride concentration, might be better indicators of visceral fat accumulation and an adverse metabolic profile than BMI alone, since BMI is a measure of general adiposity. According to Dr Mike Knapton, the associate medical director of the British Heart Foundation, however, 'no matter how you measure it, obesity is bad for your heart'.
The study concludes that the adiposity measures, whether assessed singly or in combination, do not importantly improve prediction of cardiovascular risk when additional information is available on blood pressure, history of diabetes, and lipids.
Separate and combined associations of body-mass index and abdominal adiposity with cardiovascular disease. The Emerging Risk Factors Collaboration The Lancet, Early Online Publication, 11 March 2011