BMI, BCA, blood pressure and my health

I recently purchased a Taylor Body Fat Analyzer scale from Costco (they had a sale). I started to measure myself and thought that you might find the process and concepts applicable to your own circumstances.

20100408 095039 As you probably know already, your weight by itself is not a good indicator of your general health. If a 6 ft person weighs as much as a 5 ft person, one of them (or possibly both) are out of normal ranges. A better measure is the BMI, which is simply the ratio of weight to height. But even the BMI is incomplete, since different people have different percentages of hydration, fat and muscle mass. The lean mass to fat ratio is perhaps far more relevant for the general state of health of an individual and perhaps a better predictor of chances of diabetes, hypertension, heart problems and even cancer. Weight lost is made of 70% fat and 30% muscle mass, but a scale by itself cannot make the distinction.

I wasn’t thinking much of all these things when I purchased my Body Fat Analyzer, but the sale, which brought its price down to less than $20 – I could not resist. Expecting disastrous results after my increasingly sedentary lifestyle from the past few years, I was pleasantly surprised to learn that I am not a walking disaster yet.

My latest results (morning after shower) are 18.1% body fat, 57% TBW and 61% muscle mass. This compares to 18, 56 and 60 in the fall, when I had purchased the scale. But what do the numbers mean?

First of all, these measurements, as precise as they sound, are actually approximations. They are done indirectly via a method called BIA, or Bioelectrical Impedance Analysis. A harmless current is sent through your body and the resistance, coupled with the weight and age, allow it to perform the BCA, or Body Composition Analysis. Different people – different rhythms and athletes in particular have a different bone and muscle structure, so their measurements need to be adjusted and there is a similar variance between different body types, between males and females, between age groups, etc. For the purposes of this measurement, an athlete is considered a person who does 10 h or more per week of aerobic activity and has a resting heart rate of 60 beats per minute.

I am surely no “athlete”, but what is my heart doing? Well, in the not so distant past an acute episode of irregular heartbeat (arrhythmia?) got me so scared that I ended up in the emergency room. Luckily, it was a false alarm – I did not die. Such problems can be caused by a multitude of factors, including panic attacks, but one direct result of that episode is that I started measuring my blood pressure. I have also adjusted my diet to include more oatmeal and garlic, known to significantly reduce the occurrence of such problems.

Here’s what I got in my Omron memory (pressure in mmHg, pulse / min):

# date time SYS DIA pulse
1     117 79 69
2 11/23 20:21 121 81 70
3 11/24 5:46 122 83 75
4 11/24 19:06 124 81 75
5 11/25 20:29 123 84 80
6 11/26 5:37 130 86 * 84
7 11/29 22:14 123 74 75
8 6/28 5:30 105 79 80
9 7/8 0:48 117 79 69

My resting heart rate (lowest: 69) is clearly high by athletic standards. The Canadian Hypertension Society recommends a guideline for upper limit of normal for home blood pressure readings: Systolic Blood Pressure at 135 mmHg and Diastolic BP at 85 mmHg. My SYS seems fine, but my DIA comes perilously close to the limit. Still, that is a general guideline and varies with age and other factors. According to Wikipedia,

Systolic pressure is peak pressure in the arteries, which occurs near the end of the cardiac cycle when the ventricles are contracting. Diastolic pressure is minimum pressure in the arteries, which occurs near the beginning of the cardiac cycle when the ventricles are filled with blood. An example of normal measured values for a resting, healthy adult human is 120 mmHg systolic and 80 mmHg diastolic (written as 120/80 mmHg, and spoken [in the US] as "one-twenty over eighty").

Classification of blood pressure for adults
Category systolic, mmHg diastolic, mmHg
Hypotension
< 90
< 60  
Normal
 90 – 120
and 60 – 80  
Prehypertension
121 – 139
or 81 – 89 
Stage 1 Hypertension
140 – 159
or 90 – 99 
Stage 2 Hypertension
≥ 160
or ≥ 100 

Differences between left and right arm BP measurements tend to be random and average to nearly zero if enough measurements are taken. However, in a small percentage of cases there is a consistently present difference greater than 10 mmHg which may need further investigation, e.g. for obstructive arterial disease.

The risk of cardiovascular disease increases progressively above 115/75 mmHg. In the past, hypertension was only diagnosed if secondary signs of high arterial pressure were present, along with a prolonged high systolic pressure reading over several visits. In the UK, patients’ readings are considered normal up to 140/90 mmHg.

Clinical trials demonstrate that people who maintain arterial pressures at the low end of these pressure ranges have much better long term cardiovascular health. The principal medical debate concerns the aggressiveness and relative value of methods used to lower pressures into this range for those who do not maintain such pressure on their own. Elevations, more commonly seen in older people, though often considered normal, are associated with increased morbidity and mortality.

Obviously, I need more exercise. Perhaps I should look into ways of writing articles while bicycling. Idea

Going back to my BCA scale, here’s what their manual had to say:

Taylor BCA scale manual

The above chart seems to match those of the American Council for Exercise, as quoted by wikipedia:

Description Women Men
Essential fat 10–13% 2-5%
Athletes 14–20% 6-13%
Fitness 21–24% 14–17%
Acceptable 25–31% 18–24%
Obese 32%+ 25%+

Though my blood pressure readings paint a different story, my fat is “acceptable” to “fit”. Where do YOU fall on the charts?

Sources / More info: BMI calculator, wiki-body-fat, about-body-fat, wiki-blood-pressure, wiki-body-water

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