There are quite a few methods to measure a person’s body fat. All methods require special equipment and trained personnel. Some of these methods are:

Underwater weight: This method weighs a person underwater and then calculates body fat based upon the amount of displaced water.

BOD POD: The BOD POD is a computerised, egg-shaped chamber. After the person enters the BOD POD, the amount of displaced air is used to calculate body fat.

DEXA: Dual-energy X-ray absorptiometry (DEXA) is similar to a bone scan. It uses X-rays to determine not only the amount of fat but also the location of fat in the body.

Skin calipers: The skin fold thickness in several parts of the body is measured with calipers, a metal tool similar to forceps.

Bioelectric impedance analysis: Another seemingly simple method involves standing on a special scale with footpads. A harmless amount of electric current is passed through a person’s body and analysed.

However, these methods can yield inaccurate results if an inexperienced person performs them or they are used on someone with significant obesity.

Weight/Height Tables

Because measuring a person’s body fat is tricky, there is often reliance on other means to diagnose obesity. Two widely used methods are based on weight-for-height tables and body mass index. While both systems have their limitations, they are reasonable indicators that someone may have a weight problem. The calculations are easy and no special equipment is required.

Most people are familiar with weight-for-height tables. Doctors and nurses (and medical insurance agents) have used these tables for decades to determine whether someone is overweight. The tables usually have a range of acceptable weights for a person of a given height.

One small problem with using weight-for-height tables is that doctors disagree over which is the best table to use. Many versions are available, with different weight ranges. Some tables take a person’s frame, size, age, and sex into account. Others do not.

A grave limitation of all weight-for-height tables is that they do not distinguish between excess fat and muscle. A very muscular person may appear obese, according to the tables, when he or she is not! For instance, if you are 5 feet 4 inches tall, you can be considered obese when you weigh 80 kilos or more.

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