Fitness Testing: Body Composition
Body composition assessment can be difficult to discuss fairly because it is so intimately tied with our body perception and even our sense of self worth. However, it is an important subject because body composition results are strongly predictive of your risk coronary heart disease, several types of cancer, stroke, diabetes, osteoarthritis, high blood cholesterol, and high blood pressure.
To understand your results, keep in mind that scientists typically divide body weight into fat weight and fat-free weight. The fat-free weight is primarily muscle, bone, and water.
The preferred measure of body composition is the ratio of fat weight to overall weight. For example, your bodyfat composition results are likely to have been expressed as a percentage (e.g. 22%). This is the percentage of fat weight relative to your overall body weight. This percentage gives a sense of how much of your body is devoted to using energy for moving and living (fat-free mass) and how much is devoted to storing energy (fat).
As you have likely heard before, some bodyfat is essential for healthy living. Your energy production and neurological systems, in particular, will not operate properly without some lipids (fats) in your diet and on your body. However, the problem is that many people simply have far more bodyfat than is needed or appropriate for healthy living. In a clinical setting, the terms "slightly overfat", "fat" and "obese" are used to describe degrees of this excess fat accumulation.
While our standards (or "norms") for fat are typically higher for people as they age (especially into their 40s and 50s), the following table represents a reasonable consensus view for the classification of fat levels for adults.
|
Men |
Women |
| Lean |
<8% |
<13% |
| Optimal |
8-15% |
13-23% |
| Slightly Overfat |
16-20% |
24-27% |
| Fat |
21-24% |
28-32% |
| Obese |
>= 25% |
>= 33% |
In reviewing this chart, it is essential that you distinguish between issues of body image versus issues of health. It is quite common for both men and women to be within the optimal bodyfat range and yet still be unhappy with their body image. However, it is also true that people may be perfectly healthy even into the "Slightly Overfat" range if they are otherwise active and eat well. Similarly, some people discover that their bodyfat level is quite high even though their overall weight is quite low and, from external appearances, they are quite slim. This occurs when both activity level and food consumption are so low that lean body weight falls to a very low level. Since health outcomes are predicted by the ratio of bodyfat and not the quantity of bodyfat, appearance alone is often not the best indicator of health risk.
As a side note, most male endurance athletes fall under 10 percent body fat, while the threshold for females is 17 percent and under. Bodyfat values under 4 percent for men and 10 percent for women are considered dangerous and unhealthy.
Other Body Composition Measures
Years ago height-weight tables were popularly used to provide recommended weight ranges for a certain height. These tables and a related measure, Body Mass Index (BMI) still play a role in health screening but they provide only a very rough estimate of one's ideal or healthy body weight. For example, athletic individuals with large amounts of fat-free weight (muscle) are usually defined as "overweight" when using these methods despite having low amounts of body fat and being quite healthy. At the same time, those with small amounts of muscle and bone can often be designated as "underweight" when in actuality they may be carrying too much body fat. For these reasons, these methods are typically not used when a true bodyfat measure is available.
More recently, researchers have created other measures such as the Waist-Hip Ratio and the Waist Circumference measures so that they can capture information about where excess fat is deposited. This is in response to research showing that health risks are most common in individuals whose excess fat is deposited in abdominal areas rather than the hip and thigh areas. In other words, health risks are greater for those who have much of their body fat in the upper body, especially the trunk and abdominal areas. This is called android obesity (or apple-shaped) in comparison to gynoid obesity (or pear-shaped, characterized by deposition of fat in the hips and thighs). The ratio of waist and hip circumferences (WHR) is a simple and convenient method of determining the type of obesity present. The risk of disease increases strongly when the WHR of men rises above 0.9, and of women, above 0.8.