It is known that BMI (Body Mass Index) has been used to measure an adult's height compared to their weight. When the figure reaches a certain level, one would be considered as overweight or obesity, which may lead to higher risk of health-related problems.
If you use U.S. units for calculating BMI, use this formula:
BMI = (weight in lbs. X 703) ÷ (height in inches squared)
For example, if you are 172 lbs. in weight and 6 feet 1 inch tall:
Your BMI = (172 X 703) ÷ (73 X 73) = 22.7
If you use metric units for calculating BMI, use this formula:
BMI = weight in kg ÷ (height in meters squared)
For example, if you are 78.2 kg in weight and 1.85 meters tall:
Your BMI = 78.2 ÷ (1.85 X 1.85) = 22.8
Decide where the resulting BMI fits on the scale from underweight to obese:
Underweight: 17.9
Normal: 18 to 25
Overweight: 25.1 to 29.9
Moderately obese: 30 to 40
Severely obese: More than 40
Apart from the traditional BMI-based measurement of human weights, however, scientists have studied on the effects that another concept, central obesity, has on human health.
Central obesity has nothing to do with BMI. Instead, it is reflected by high waist circumference (WC). In other words, you may have central obesity due to belly fat even though your weight is normal.
Central obesity, though common in the general population, can bring a higher risk of all-cause, cardiovascular disease, and cancer mortality among postmenopausal US women.
A nationwide cohort study of postmenopausal women
A recent research published in The Journal of the American Medical Association (JAMA) studied more than 156 thousand postmenopausal women enrolled in the Women's Health Initiative.
The results of the study
Among 156,624 postmenopausal women with an average age of 63.2 years, nearly 40 thousand death occurred, with 29.6% death from cardiovascular disease and 27.0% death from cancer.
If we consider the hazard ratio of all-cause mortality for women with normal weight and no central obesity as 1, the hazard ratio of other groups of women were:
| normal weight | overweight | obesity |
|---|
| no central obesity | 1 | 0.91 | 0.93 |
|---|
| central obesity | 1.31 | 1.16 | 1.30 |
|---|
When the figure is less than 1, it means the hazard ratio of death of that group of women is lower than that of women with normal weight and no central obesity; when the figure is more than 1, it means the hazard ratio of death is higher. The higher the figure is, the more risk of death the group of women face.
Compared with normal weight without central obesity, normal-weight central obesity was associated with higher risk of cardiovascular disease mortality and cancer mortality.
Women with normal weight and central obesity had a similar risk as women with BMI-defined obesity and central obesity, which means central obesity can cause great health problems just like BMI-defined obesity.
BMI-defined obesity V.S. central obesity
Current public health guidelines for obesity focus on promoting a normal BMI, and seldom mention abdominal fat. Indeed, BMI can measure weight-based obesity, but it ignores factors such as body shape or body fat.
The results suggest the importance of keeping not only a normal weight, but a normal waistline. Since central obesity has a greater health effect, as the reasearch reveals, you may want to pay more attention to control your belly fat.
More things you need to know
To see why you are overweight, check Easy to Put On, Hard to Lose: Why Am I Overweight?
To see how to treat obesity, check Want to get rid of obesity? One article tells you everything
