The Relationship Between Blood Pressure and BMI
Your blood pressure and BMI are interrelated, in a way, because BMI is one measure of obesity -- a chief risk factor for hypertension.
Once you understand the basic causes of hypertension, the relationship between blood pressure and BMI, or body mass index, becomes fairly obvious. This is because BMI is one of the key measures for determining obesity. And like it or not, obesity -- simply being overweight, as most Americans are -- is one of the prime risk factors for hypertension.
Hypertension and Weight
Unfortunately, a person carrying around excess weight tends to have a higher BP than they would if they were thinner, simply because the extra weight puts a strain on their cardiovascular system (not to mention the rest of their body).Older people, or those who have inherited a propensity for heart disease, may find their BPs pushed into the danger zone if their weight gets out of hand. But how much weight is too much? There's no hard and fast rule for that, which is where the BMI comes in.
The BMI Formula
BMI is simply a measure of your weight relative to your height. In Imperial measure (inches and pounds), the formula is: BMI = weight in pounds times 703 divided by height in inches, squared.
So if you weigh 200 pounds and you're 60 inches tall, your BMI = 200 x 703/(60*60) = 140,600/3600 = 39 -- which, incidentally, is very high.
For metric measures, it's a bit easier to calculate: BMI = weight in kilograms divided by height in meters, squared.
So let's say you weigh 73 kilograms (160 pounds) and stand two meters tall (six and one-half feet). In this case, BMI = 73/4 = 18.18...which means you're too skinny.
If you'd like an easier way to check your BMI, just plug the numbers into this online BMI calculator
So What's the Deal?
In general, here's how the BMI falls out:
• Less than 18.5: Underweight
• 18.5-24.49: Normal
• 24.5-29.9: Overweight
• 30+: Obese
A BMI over 24.49 puts you at significant risk of hypertension, especially if you have other risk factors like diabetes or abnormal cholesterol, or if you're over 65, have a family history of heart disease, rarely exercise, or overuse tobacco.
Be aware that your BMI is not a failsafe determination of your risk for hypertension. It may overestimate body fat if you're very muscular or suffering from fluid retention, and may underestimate body fat if you're older or losing muscle.
This is where checking your waist measurement is important. A measurement of over 40 inches in men and 35 inches in women is a cause for concern.
So while blood pressure and BMI don't necessarily go hand in hand, when taken into account with waist measurement, BMI does offer a good rough estimate of hypertension risk.