Racial and age differences in body fat testing and simplified health assessment methods
Ultrasonic method
The principle of ultrasound is to send ultrasound waves through the skin and fat. When it encounters denser, fat-free tissue, the waves bounce back, and the instrument picks up the information. Essentially, this method is the same as skin diameter measurement, so their measurement results, average errors, and the problems they face are largely the same. The major difference lies in the fact that the information from ultrasound is processed by a computer and then printed out in a very sophisticated manner. This processing makes ultrasound seem much more scientific.
Underwater Immersion Method
For most people, underwater immersion is the standard method for analyzing body composition. If every step of the test is performed correctly, the results will accurately reflect the ratio of body fat to lean tissue. However, hydrophobia, gas in the body (in the lungs, intestines, or even in the hair or clothing), and abnormal water conditions can all affect the accuracy of the results. I once tested Jack. His first test showed a body fat percentage of 15%. After six months of hard work, exercise, and a planned diet, he looked much slimmer, and I estimated his body fat percentage should have dropped to 10% or 12%. But the night before his second test, he ate three bowls of red chili beans, which caused him to swell and fill his stomach with gas. As a result, he floated in the tub during the test, and his body fat percentage was as high as 23%. I was convinced this result was incorrect, so a week later, I tested him again. This time, he didn't float, and his body fat percentage was 12%.
Here's another situation that can lead to incorrect test results, one that even experienced testing experts struggle to avoid. Women often experience bloating before menstruation, not entirely due to increased fluid levels, but sometimes due to gas in the digestive system. This can cause the measured fat level to be 2% to 3% higher than the correct value. After three days, the gas dissipates, and the fat level naturally returns to normal.
Some people who have previously conducted underwater immersion tests attempt to manipulate the results during subsequent tests. This behavior is considered ridiculous by the staff, as it only worsens the outcome. For example, some people fast for several days before the test, rapidly losing several kilograms in the hopes of lowering their body fat percentage. However, most of this weight loss is water, which lacks fat tissue, thus only increasing the perceived percentage of body fat.
Reasons for deviations in the underwater immersion method:
• Do not drink water before the test to reduce the body's water content.
• Consume beans or other gas-producing foods and drinks before the test.
• Excessive exercise before the test.
• When submerged underwater, do not exhale all the air.
The correct way to perform underwater immersion:
• Consume low-fat foods for 4 months prior to the test.
• Continue aerobic exercise for 4 months prior to the test.
• If you want to increase the percentage of fat-free tissue, add some weight training to your exercise program.
Maintain good eating habits before the test.
• Sew some lead metal into the swimsuit.
Race, age and gender speculation
During the years I was promoting the underwater immersion method, I tested it on approximately 25,000 people. Although I often told my audience not to judge body fat percentage by appearance, I myself was adept at estimating a person's body fat percentage by sight and touch. Visual estimation is often misled by appearance; we tend to assume that thinner people have lower body fat percentages and obese people have higher percentages. Another popular method is the "pinch test," which states that if you can pinch 3 centimeters of abdominal muscle, you should lose weight. I don't reject this method because I often use it to estimate body fat percentage by hugging a person's waist or hips and feeling the elasticity of the muscles. This method usually has only a 1% to 2% error compared to the underwater immersion method.
However, these methods had a large margin of error when applied to Black people, because Black people generally appear heavier. For example, when a Black person appeared before me, after some observation, I guessed their body fat percentage was about 18%, but the test result was only 14%. Gradually, I found that my guesses about Black people were always 3% to 4% higher than the actual values. Because Black people have a higher bone and muscle density than White people, they appear heavier in water. Therefore, if the standard body fat percentage for White women is 22%, then for Black women it should be 19%. It wasn't until 1985 that a corrected formula based on the physique of Black people was officially developed.
Furthermore, East Asians have lighter bones than Westerners, so measurements of East Asians should be adjusted accordingly. Because of the lower density of adipose tissue, East Asians float more easily in water. According to the commonly used Kirkpatrick formula, the actual fat content of East Asians should be about 3% less than the formula's value.
I've also observed another phenomenon, though it hasn't been confirmed in professional journals yet, but I believe it will be proven in the near future: Like Black people, people of color have a higher density of lean tissue. Therefore, if calculated using the Koch formula, the resulting fat percentage will be 3% lower than the actual percentage. Have you ever noticed the composed demeanor of Black or Red people when playing football or boxing? Conversely, people of East Asian descent, with their smaller frames, are usually better at light sports such as swimming and gymnastics.
The original percentage values for the Kirkpatrick formula were obtained by studying the corpses of young white people, so the revised standard values are only meaningful when racial factors are taken into account.
Furthermore, children's test results can be somewhat inaccurate because children have lower levels of water and bone minerals in their lean tissue compared to adults, leading to test values that are 4% to 5% higher than the actual values. Generally, a child's body fat percentage is around 15%. However, with the onset of puberty, boys' lean tissue percentage increases significantly, while girls tend to gain weight gradually. Around age 18, a healthy, active boy's body fat percentage is approximately 10% to 12%, while a girl's is around 19% to 22%.
Similarly, for people over 50, the loss of bone minerals and muscle will cause errors in the formula. A higher body fat percentage may be due to the reduction of adipose tissue, and does not necessarily mean that there is too much fat.
A healthy woman's body fat percentage is between 19% and 25%, but the average for women is between 30% and 33%. Ten years ago, before body fat testing was widespread, there was a prevailing belief in the sports world that the standard body fat percentage for athletes, both men and women, should be 6%. To help athletes reach this standard, some coaches designed various diet plans, and some even punished or dismissed athletes who didn't meet the target. In most cases, a 6% body fat percentage is only healthy for men, but too low for women, although there are certainly exceptions. In fact, most male athletes have a body fat percentage between 5% and 13%, and women between 12% and 22%. This misconception is difficult to avoid even for experts in the field, let alone untrained individuals!
Gradual weight loss is the safest method because it only reduces fat without losing any muscle. I recommend that you don't lose more than 0.5% of your body weight each month.
In any case, I am truly horrified for those who misunderstand body fat testing methods, because they always mistake the standard fat percentage value for the average fat percentage value, or get frustrated by the simple test value, completely ignoring the fact that their bodies are actually in the best condition.
I'm concerned that some people might overreact to the test results. For example, Anna's body fat percentage was 26%, but experts calculated her ideal value to be 22%, meaning she needed to lose 3 kilograms. She became overly concerned with these numbers, and ultimately, excessive exercise and improper dieting caused her to lose 3 kilograms of muscle. In reality, her lean body percentage was already low; she should have focused on building muscle, not losing fat. Furthermore, the testing process can be flawed, and as the examples above show, race, age, time of day, skin color, and even hair color can all influence the results.
If you've ever had a body fat test, don't take that number as an absolute standard. Remember, these testing methods themselves have a 3% to 4% margin of error. If your body fat percentage is indeed high, then design a gradual weight loss plan! I suggest you set your weight loss goal at no more than 0.5% per month. If your diet and exercise are normal, but your test results are consistently 2% to 3% higher than the standard value, then don't worry, because you might just not be suitable for using the Kirkpatrick formula! Instead of torturing yourself mentally and physically, accept it calmly and treat it as a standard to maintain for the next few years!
Simple health test method
If a car travels at 96 kilometers per hour, that means it travels 1.6 kilometers per minute. The famous runner Roger Bannister was the first person in the world to run 1.6 kilometers in 4 minutes. When I was a graduate student at MIT, my long-distance running goal was to run 1.6 kilometers in under 6 minutes. Now, I don't know how fast I can run anymore, especially after turning 50. But I know my jogging speed range very well: when I'm in a good mood, it takes me about 8 minutes to run 1.6 kilometers, but at higher altitudes or when I'm in a bad mood, it takes about 10 minutes. Women typically take about 15 minutes to run 1.6 kilometers, and some even take half an hour.
A healthy person can easily run 4 kilometers in 20 minutes, while a person in poorer health can only easily run 1.6 kilometers. This is because people have already established a comfortable pace when walking, jogging, or running. Running at this pace will not only prevent them from feeling exhausted, but will also prevent muscle soreness the next day.
One important thing is that you must be able to distinguish between a "comfortable pace" and a "forced pace." Your daily exercise pace should allow you to maintain your fastest pace for a period of time (say, half an hour) without causing exhaustion or muscle soreness. I often advocate in my speeches: "Even on the first day of a running program, you should still run as fast as possible... but the premise is that the running speed must allow you to comfortably complete the run within half an hour and not cause muscle soreness the next day." When the cardiologists in the audience hear my first sentence, they are often shocked because they worry that it might cause heart attacks in people with poor health. However, after hearing my second sentence, they breathe a sigh of relief.