Body composition

Body composition refers to the proportions of fat and lean tissue that make up total body weight. Lean tissue is made up of muscles, organs and bones.

Direct measures of body composition are impossible in human beings. Therefore body composition is indirectly based on the assumption that body weight is made up of body fat and lean tissue.

Changes in weight do not reflect how the body's composition may have changed, and yet most people use weight to assess their level of "fatness."

Overweight does not necessarily mean overfat. For instance, an athlete may have well-developed muscles and heavy bones but little body fat. Because muscle is heavier than fat, the athlete may be classified as overweight by some standards, but actually has a very healthy level of body fat. On the other hand, an inactive person may be classified as having a healthy weight, but may actually have too much body fat compared to lean tissue.

It is critical that the concept of body weight and body composition is understood. A general goal for improving health would not be to simply reduce the amount of total kilograms that you weigh, but rather to focus on reducing your amount of body fat and/or increasing your lean body mass to obtain a healthy body composition. For this reason, the scale is NOT an ideal tool for measuring progress. Body measurements and the fit of your clothing are much more accurate indicators of progress.

Body weight

·    How much should you weigh?

·    How do you know if your weight is appropriate for your height?

·    How do you know if your weight is affecting your health?

Healthy body weight is defined by:

·    A weight within the recommended range for height

·    A fat distribution pattern that is associated with a low risk of illness and early death

·    A medical history that reflects no risk factors associated with obesity. These include raised blood cholesterol, blood glucose (sugar) or blood pressure.

Health care professionals often compare weight with standard weight-for-height tables. Although these tables are commonly used, they are not the recommended method of evaluating your body. Using the Body Mass Index (BMI) to assess your body weight and progress over time is far more preferable.

Body Mass Index (BMI)

BMI describes your weight in relation to your height. BMI = weight (in kilograms) divided by height (in metres)squared.

To calculate your BMI visit...

Body fat

The ideal amount of body fat depends on the individual. You can use your health to help you determine how much body fat you should have. In other words, you should have enough fat to meet your body's basic needs, but not so much that your health is at risk.

In general, health problems usually develop when body fat exceeds a certain limit:

·    Young men: 22%

·    Men over 40yrs: 25%

·    Young women: 32%

·    Women over 40yrs: 35%

A healthy body contains enough lean tissue to support your health and the right amount of fat to meet your body's needs.

Body fat distribution

The pattern of distribution of body fat may play a more important role in your health than the actual amount of body fat. Body fat that is stored around the organs of your abdomen is associated with increased risks of heart disease, diabetes, high blood pressure and some types of cancer. People with predominantly upper-body fat are sometimes referred to as "apple-shaped," while those with predominantly lower-body fat are referred to as "pear-shaped."

Waist circumference

Since body fat that is stored around the organs of your abdomen is associated with increased risks of diseases, fat around the abdomen or waist has been shown to be more dangerous to your health than weight carried on your hips and thighs. For this reason, waist circumference is used to measure health risks.

To assess your waist circumference refer to Step 1 of My Nutrition Programme.

Other methods of assessing your body

There are other techniques used by healthcare professionals to determine body fat and its distribution. These include skinfold measurements, bioelectrical impedance and hydrodensitometry.

Skinfold measurements involve the use of an instrument called a calliper, which measures the thickness of the skin on the back of the arm, below the shoulder blade and in other places on the body. These measurements are then compared to standards to determine whether the amount of fat is within a healthy range or not.

Bioelectrical impedance uses a low-intensity electrical current to determine the percentage of body fat versus lean body tissue. This is calculated through the amount of resistance there is to the current by the various tissues in the body.

Hydrodensitometry involves weighing a person first in the normal way (on a scale on land) and then again when submerged in water. The difference between the person's weight on land and their weight under water provides an indication of their body volume. A calculation is used to estimate body fat percentage from body density.

Body type

Body type (or somatotype) is your genetically predetermined shape. It is a combination of your lean muscle distribution and your bone structure. Body types have unique hormonal and metabolic characteristics - in other words, people have different types of metabolism.

During the middle of the twentieth century, William H. Sheldon (a Harvard psychologist) categorised the physique of people and developed three basic body types:

·    Endomorph (also called lymphatic)

·    Ectomorph (also called thyroid)

·    Mesomorph (also called android)

Generally, people can be classified as one of these body types, or they can have a combination of characteristics of each.

Sources:

Understanding Nutrition (Rolfes & Whitney)

Food, Nutrition & Diet therapy (Mahan & Arlin)

Manual of Dietetic Practice (Thomas for the British Dietetic Association)

(Reworked from article by Discovery)