Are you too fat or not? You’re better off answering this question with a tape measure than a weighing scale. According to obesity researchers at the Pennington Biomedical Research Center, your waist measurement says more than your BMI. They published their findings in the International Journal of Obesity.
Waist versus BMI
You measure your waist at the narrowest part of your middle, placing the tape measure just above your pelvic bone. If adult women have a waist measurement of 89 cm or more they have too much fat and therefore an increased risk of diabetes and cardiovascular disease. For men the cut-off point is 102 cm.
Most nutritionists and scientists prefer not to use waist measurement as an indication that someone is too fat; they prefer to use the BMI. The Body Mass Index is calculated by dividing your bodyweight in kg by the square of your height in metres.
Another measurement is waist-hip ratio. This is waist measurement divided by hip measurement at the widest point. Men are too fat if the ratio is above 0.9; for women the cut-off point is 0.85.
There is much discussion about which criteria gives the most accurate indication of whether you need to lose weight or not. BMI is under attack because recent studies have shown that an individual with a BMI that is well within the limits, but with a bigger waist measurement is not necessarily healthy. [N Engl J Med. 2008 Nov 13;359(20):2105-20.]
Waist measurement says more about health than BMI
The researchers at Pennington studied which of the forms of measurement – the BMI, waist measurement or waist-hip ratio – was the best predictor of mortality. They used data that had been gathered for the Canadian Heart Health Survey Follow-Up Study, in which about 8,000 men and women were monitored for an average of thirteen years. The researchers knew which participants had died and what the cause of death was. They also knew the BMI, waist circumference [WC] and waist-hip ratio [WHR].
This enabled the researchers to calculate the relationship between BMI, WC and WHR on the one hand and risk of dying on the other. The results are shown in the figures below. An asterisk indicates a statistical relationship. The more asterisks, the stronger the relationship. The message is clear: your waist measurement gives the best indication of whether you need to lose weight.
“Waist circumference consistently exhibited the most prominent association with mortality risk for all-cause, cardiovascular disease and cancer mortality compared with weaker associations for BMI and waist–hip ratio”, the researchers conclude.
“Results indicate the need to account for waist circumference in examining the relationship between adiposity and mortality. The clinical importance of maintaining a low waist circumference regardless of BMI bears significant implications for preventing premature mortality attributable to cardiovascular or cancer complications.”
Body mass index versus waist circumference as predictors of mortality in Canadian adults.
Elevated body mass index (BMI) and waist circumference (WC) are associated with increased mortality risk, but it is unclear which anthropometric measurement most highly relates to mortality. We examined single and combined associations between BMI, WC, waist-hip ratio (WHR) and all-cause, cardiovascular disease (CVD) and cancer mortality.
We used Cox proportional hazard regression models to estimate relative risks of all-cause, CVD and cancer mortality in 8061 adults (aged 18-74 years) in the Canadian Heart Health Follow-Up Study (1986-2004). Models controlled for age, sex, exam year, smoking, alcohol use and education.
There were 887 deaths over a mean 13 (SD 3.1) years follow-up. Increased risk of death from all-causes, CVD and cancer were associated with elevated BMI, WC and WHR (P<0.05). Risk of death was consistently higher from elevated WC versus BMI or WHR. Ascending tertiles of each anthropometric measure predicted increased CVD mortality risk. In contrast, all-cause mortality risk was only predicted by ascending WC and WHR tertiles and cancer mortality risk by ascending WC tertiles. Higher risk of all-cause death was associated with WC in overweight and obese adults and with WHR in obese adults. Compared with non-obese adults with a low WC, adults with high WC had higher all-cause mortality risk regardless of BMI status.
[corrected] BMI and WC predicted higher all-cause and cause-specific mortality, and WC predicted the highest risk for death overall and among overweight and obese adults. Elevated WC has clinical significance in predicting mortality risk beyond BMI.
PMID: 22249224 [PubMed – indexed for MEDLINE] PMCID: PMC4120111