Sunday, 24 November 2013

"The weight of our nation : India" series part 5 (anthropometry)

PART 5  of the series in

 "The weight of our nation:



In the simplest terms anthropometry is measurement of the human body; it helps in identification of under or over nutrition. It is also used as a screening tool to evaluate adequate growth.

This is done by maintaining a growth chart, where height, weight, age, head circumference, waist-hip ratio are all taken into consideration. This can also be done by taking measurements and using anthropometric tools and ratios such as, skin fold calipers and waist hip ratios. This is then compared with the general height and weight standard of the population. This helps evaluate if a person, child or adult is healthy and adequately nourished.

Skin fold thickness helps estimate the subcutaneous fat. (Fat that lies directly beneath the skin)
This is an estimate and hence doesn’t help with the knowledge of one’s body composition.  Hence there are anthropometric body assessment techniques.

1.    DEXA Duel Energy X-ray Absorptiometry
This estimates fat free mass as well as lean mass. It is used as a research in clinical studies even though its accuracy is very good. However it causes radiation exposure.

2.    Bioelectrical Impedance (BIA)
This estimates the percentage of body fat depending on conductivity of tissue fluid and electrolyte content by applying a small alternating current. This method is not that accurate in measuring the body composition of obese children. The benefits of BIA are that it does not require a specially trained professional and it is a non-invasive method, comparatively inexpensive when compared to MRI and DEXA. This is also available at small house hold scales.

3.    Ultrasound
This measures the subcutaneous fat percentage. It is used in clinical and research settings.

4.    Bod Pod
This works on the principle of air displacement. This method is supposed to be very accurate in determining body fat percentages, although it underestimates body fat in children. Hydrostatic weighing is based on this similar principle but performed under water and hence measures water displacement.

5.    Total Body Electrical Conductivity
This is used to determine body composition and fat free mass. This works on the principle of disruption of magnetic field by electrolytes. This is quick method and there is no risk of radiation exposure.

6.    CT and MRI
CT is Computed Tomography and MRI is Magnetic Risonance Imaging. These are expensive methods to determine the body composition, and requires trained  professionals. Unfortunately it causes radiation exposure. It is used in clinical and research settings.

7.    Deuterium
This measures total body water to further calculate fat percentages. This is not a commonly used method because of the equipment time and technicians it requires. It is also not radioactive and is used for research purposes.

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