Measuring the body – Part 1: Anthropometry
Overview
Measurement of body dimensions (weight, height, etc) is called anthropometry. These figures are essential to help us manage diet and lifestyle programmes.
We have normal ranges for each parameter, and health indices based on their ratios. In the general population, these measurements are very useful and help doctors tell you, for example, if you are at risk of diseases like diabetes or heart disease because of your weight.
For example, body mass index (BMI) looks at body weight according to height; the risk of chronic disease has been shown to rise as BMI increases.
Yes, it is true that these measures need to be interpreted with caution in certain individuals, such as athletes and bodybuilders. But this does not mean they are not useful in the vast majority of individuals.
The most important anthropometric measurements in weight management are height, weight and waist and hip circumferences. There are many more measurements, but these four and the relationships between them will immediately give us a very good idea of health and health risks in most people.
What you should be aware of
BMI (weight/height2)
Waist circumference
You should take these measures (or have them taken) regularly as part of your general care. The earlier any risk is detected, the earlier steps can be taken to help.
One of the very few drawbacks of anthropometry is that it does not tell us about body composition, i.e. how much of body weight is fat, how much is muscle, etc. We now have devices able to tell us this. I talk about this in another article (See here for bioelectrical impedance body composition analysis).
If you would like to know more about anthropometry, please read on.
The Details
The main anthropometric measurements used in weight management:
- Weight
- Height
- Waist and hip circumferences
Numerous other anthropometric measurements are available but are only necessary in specific circumstances.
Weight
Weight is a basic measurement and should be measured to +/-100 g. Greater accuracy can be sought but is rarely relevant in this context as the time since your last glass of water or since you last urinated is going to affect weight by at least that much.
It is important to maintain consistency in the method, always using the same scales and attempting to take the measurement in the same conditions each time (e.g. on getting up in the morning, in light underwear and after urinating).
How often?
Whilst we should not become obsessed with weighing ourselves, it has been shown that regular self-monitoring of body weight increases awareness about how certain behaviours affect our weight. This can promote self-correction. I suggest weighing yourself 2 or 3 times a week (and taking action if you notice that your weight is starting to creep up!).
Height
Height is obviously essential to be able to interpret weight. There is a huge difference between two people weighing 12 stone, if one of them is 6 inches taller than the other. Height is included in two of the most important indices for the interpretation of body weight: body mass index and waist-to-height ratio.
Circumferences
We can measure numerous body circumferences, but the particularly useful ones in weight management are waist and hip circumferences. These are used to compare against each other and against height to provide information about body shape and fat distribution (see below and here.) Other circumferences, such as of the neck, upper arm or thigh, can also be useful in certain cases.
Skinfolds
Skinfold thickness is not routinely measured since the introduction of body composition analysis.
Skinfolds are measured using callipers. A pinch of skin that includes the subcutaneous fat is measured at different sites on the body, and the results are entered into formulae to give us an estimation of general adiposity (fat content of the body). Visceral fat is not estimated by this method. Skinfold thickness becomes inaccurate in obesity due to the difficulty of picking up a representative fold of skin and subcutaneous fat.
FORMULAE
The main formulae used in weight management:
- Body mass index
- Waist-to-hip ratio
- Waist-to-height ratio
Body Mass Index: The body mass index (BMI) is your weight in kg divided by your height (in metres) squared. The ranges for underweight to morbid obesity have been widely published:
In most adults this is a very useful index as it has been shown to be closely linked to the risk of obesity-related chronic diseases, such as diabetes and heart disease. However, there are exceptions to its applicability, such as in athletes (this index would class any Mr Universe as obese) and children. Also, the correlation between BMI and the risk of certain diseases varies with ethnicity; for example, persons of Asian descent are more likely to develop diabetes at lower BMIs.
Finally, the BMI does not inform us of the body composition, and some people who are of normal weight according to the BMI can have a high fat percentage that puts them at increased risk of weight-related disease. Identification of these individuals requires specific tests (see article on body fat percentage here.)
Waist-to-hip ratio: The waist-to-hip ratio (WHR) compares your waist circumference to the circumference at the level of your hips. This tells us about fat distribution in the body. Women are more likely to accumulate fat around the hips whereas men tend to gain fat in the abdomen, leading to the so-called gynoid or android fat distribution. This difference is very important because abdominal fat has a much closer association with heart disease, diabetes and other chronic diseases. The health risk values associated with the WHR differ between men and women:
Waist-to-height ratio: The waist-to-height ratio (WHtR) compares your waist circumference to your height. This ratio has been shown to give us a very good estimate of “central” obesity, meaning that it is useful for detecting individuals who have put on fat in the abdominal region, which is associated with an increased risk of chronic disease.
The accepted cut-off value is 0.5. Higher figures suggest a significant increase in the risk of diabetes, heart attack or stroke. The cut-off value of 0.5 is valid across different ethnic groups.
CONCLUSIONS
Anthropometric measurements are important, but it is equally important to make the correct interpretation. Trust your health professional to guide you in understanding the association between your anthropometric measurements and your health. This will help you develop the most suitable approach to achieve a healthy weight and body composition and thus maintain well-being and reduce your risk of chronic disease.
