Body Fat and Health Risk
Why would you want to know how much body fat you have? Having too little or too much body fat can be unhealthy.
Too little body fat:
- Is linked to problems with normal, healthy functioning in both men and women.
- Can lead to problems with reproduction in women.
Too much body fat:
- Increases the risk of many diseases, including type 2 diabetes, high blood pressure, stroke, heart disease, and certain cancers.
- When located around the abdomen, increases the risk even further of developing the above conditions.
Diseases associated with an excess of body fat worsen as the amount of body fat increases. However, now for the good news: When body fat returns to within acceptable ranges, the body can return to normal healthy functioning and the risk for developing the diseases mentioned above decreases.
Please note: The information in this section is not appropriate and will not be accurate if you are under 18 years of age, elderly, frail and sedentary, pregnant, lactating, or, in some cases, a body builder.
Just about everybody is familiar with the bathroom scale that measures body weight. We then usually look up our body weight on weight tables typically found in doctors' offices or diet books.
The weights on the tables are those that are associated with the lowest death rates in a group of people who bought life insurance and then were followed until they died many years later. The range of weights for each height was determined by looking at how long these people lived. The tables were originally published in 1951. They were updated in 1983, but have not been updated since. Here are the pros and cons of the weight tables.
- It's easy, simple and fast.
- The tables were easily and widely distributed.
- The number of people studied to develop the tables included millions of people.
- The weights are based on a select group of people who bought life insurance. These people tend to live longer, be healthier, and to weigh less than the general population.
- Body weight gives no information on the amount and location of body fat.
- The information used to develop the tables tends to under represent people who may be less likely to be insured: minorities, the elderly and people who earn less money.
- The tables have not been updated since 1983.
BMI (Body Mass Index)
BMI is a calculation that uses both height and weight to yield a number that correlates with an estimate of a person's body fatness. BMI standards were established using information on both illness and death. This means we can now assess a person's health risk based on that person's BMI.
- It's easy to look up on a BMI chart.
- The BMI number takes into account both weight and height.
- It appears to be a reasonable low cost substitute for assessing percent body fat.
- Health risks associated with different BMIs have been identified based on careful study.
- Up to one out of four people may be misclassified by BMI. BMI should not be used for body builders and frail, sedentary, elderly people, pregnant or lactating women, or growing children.
- BMI does not distinguish between body fat and lean body mass.
Percent Body Fat
New research connects percent body fat ranges directly to BMI. This allows us to understand health risks in terms of percent body fat.
Body fat can be measured directly only on cadavers; therefore, when a living person has body fat measured, it is an indirect measure. Many methods of estimating body fat are expensive, require special laboratory equipment, and are not readily available. There are two methods available to the general population.
These are measurements of folds of skin and fat taken at specific locations on your body. The instrument used to measure skin folds is call a skinfold caliper. The information is then entered into an equation to estimate total body fat.
- The calipers are not overly expensive.
- It does not require sophisticated equipment.
- It's portable.
- It's fast.
- It relies on as assumption that may or may not be true: the thickness of the fat below the skin is proportional to the fat stored deeper in the body.
- In adults, this measure is more accurate at younger ages. In a person's forties, the amount of fat under the skin as a percentage of total fat begins to decline.
- Some of the time, the measurements cannot be done without the help of another person.
- The amount of tissue picked up to form the skin fold can vary, so technical training is required.
- You can get different results depending on how hard you pinch the fold of skin. More expensive calipers will minimize this problem and improve accuracy.
- Since many of the equations were developed using information from normal weight people, they may be inaccurate when applied to people with excess body fat.
- If measurements are taken repeatedly over time, they may be inaccurate if different people make the measurements and they have varying skill levels.
Bioelectrical Impedance measures the resistance of body tissues to the flow of a small, harmless electrical signal. It predicts body fat from the strength and speed of the electrical signal sent through the body (impedance measurements) and information such as height, weight, and gender.
- It's safe.
- Some, but not all Bioelectrical Impedance systems, are simple and fast. · It can measure long-term changes in body fat.
- The home measurement does not require a technician so repeated measures over time can be more accurate and thus more comparable to one another.
- It tends to over-predict body fat in lean and athletic people unless the machine is equipped with an "athlete" mode with appropriate predictive formulas.
- It does not take into account the location of body fat.
A waist measurement is used to assess where your fat is distributed.
Even more important than the amount of fat is where your fat is located. Fat that is located in your abdominal area is associated with an increased risk of heart disease, high blood pressure, and diabetes. A waist circumference of 40 inches or more in men and 35 inches or more in woman is associated with significantly increased disease risk.
- It's easy, fast, and economical.
- It is a good indicator of fat distribution and health risk in adults.
- Measurements may be inaccurate. Standing can cause a shift in the position of fat in the abdomen, especially in men who have a great deal of fat in the abdomen. Doing the measurement while lying down and with the assistance of another person may provide more accurate results.
- If the tape is pulled too tightly, the measurement will be inaccurate.