What Your Scale Won’t Tell You: The Ultimate Truth About Body Fat
When it comes to body fat, many of us rely on high-tech digital scales or skinfold calipers for measurements. While these methods can give us a general idea of our body composition, they often fall short in precision. The body fat percentage they provide may not be as accurate as we think, and in many cases, it’s likely higher than what we expect. If you’ve ever wondered about the accuracy of your body fat readings, you’re not alone. In this article, we’ll dive into why your body fat percentage might not be what you think, reveal the gold-standard test for body composition, and share fascinating new data on how body fat, muscle, and bone change with age.
Why Body Fat Measurements Can Be Misleading
Most body fat measurements, whether from digital scales or skinfold calipers, are useful tools for tracking general trends over time, but they do not provide the most accurate reflection of your body composition. These methods typically lack the precision necessary to give you the true picture of your fat-to-lean mass ratio. That’s not to say these measurements are useless, however. They are valuable for assessing the effectiveness of your diet and exercise routine over time. If the numbers aren’t moving in the direction you want, it’s a clear sign that changes may be necessary.
But if you’re looking for the most accurate way to measure body composition, a DEXA scan (Dual-Energy X-ray Absorptiometry) is the gold standard.
What is a DEXA Scan?
A DEXA scan is a non-invasive test that uses low-level X-rays to measure body composition. The amount of radiation you’re exposed to during a DEXA scan is minimal and equivalent to what you would naturally absorb during a day outdoors or a short flight at high altitude. This makes the test safe for periodic use when monitoring body composition changes over time.
In addition to being the most accurate tool for assessing body fat percentage, a DEXA scan also measures visceral fat (the dangerous fat surrounding your organs) and bone density, making it a versatile and highly informative procedure.
Why Visceral Fat and Bone Mass Matter
Visceral fat is particularly concerning because it’s linked to an increased risk of metabolic diseases, such as diabetes and heart disease. On the other hand, subcutaneous fat, the fat located just under your skin, is generally considered less harmful. While a DEXA scan doesn’t directly measure visceral fat, it estimates it by analyzing the overall fat and lean mass in your body. These estimates are reliable, and studies have shown that the results can give you a clear indication of how much visceral fat you might have.
When it comes to bone mass, DEXA scans are one of the most reliable methods for measuring bone mineral density. This is especially important as we age, since bone loss—often leading to conditions like osteoporosis—becomes more prevalent with age. The ability to spot early signs of bone loss allows you to take action and potentially prevent serious health issues down the line.
Getting a DEXA Scan
You’ll need to search for a medical imaging center, sports performance center, or wellness facility in your area to schedule a DEXA scan. Costs typically range between $100 and $200 per session. During the scan, you’ll lie down on a padded bench while a robotic arm scans your body from head to toe. The process takes about 20 minutes and is completely non-invasive, so you won’t feel enclosed or uncomfortable during the procedure.
Other Methods for Measuring Body Fat
While DEXA is the most accurate body composition measurement, there are other methods that can give you a decent estimate of your body fat. The Bod Pod is another reliable tool, using air-displacement plethysmography to measure body fat. This method is more widely available than hydrostatic weighing, which used to be the gold standard but requires you to submerge yourself underwater, which many find uncomfortable.
Other methods include skinfold measurements, which can be useful if you stick with the same technician, and bioelectrical impedance (the technology used in most digital scales), which estimates body fat by sending a small electric current through your body. However, bioelectrical impedance can be less accurate, especially if your hydration status varies.
How Your Body Fat, Muscle, and Bone Change with Age
In a 2024 study, researchers in France analyzed DEXA scans from 915 participants between the ages of 20 and 93 to track changes in fat mass, lean mass, and bone density. The study revealed several key break points—specific ages when significant changes occur in these areas.
For males, fat mass increases sharply in the early 20s and slows around age 32. For females, fat mass increases gradually with age until around age 75, after which it begins to decline, likely due to increased frailty.
When it comes to lean mass, males typically maintain stable lean mass until about age 55, after which it starts to decrease. In females, however, lean mass starts to decrease around age 31.
Bone density follows a similar trajectory. For males, bone density stays stable until around age 59, while for females, there are two key periods of bone density loss: from age 47 to 62 and then again after age 82. These changes highlight the importance of staying active and building muscle and bone mass throughout life.
The Real Body Fat Percentages of Athletes
Many people associate ultra-low body fat percentages with athletes, especially in sports like bodybuilding or professional football. However, the body fat percentages of elite athletes are often not as low as people think. For instance, female NCAA Division 1 athletes in sports like basketball, swimming, and volleyball have body fat percentages ranging from 23% to 31%. Similarly, male Division 1 athletes in track and field events such as sprints and middle-distance running typically have body fat percentages ranging from 10.8% to 13.1%.
The body fat levels of professional athletes, like those in the NFL, vary significantly depending on position. For example, offensive linemen have an average body fat of 28.8%, while wide receivers maintain a leaner average of 12.5%.
What Can You Do with This Information?
The key takeaway here is that body fat percentage measurements are useful, but they’re not always entirely accurate. If you can access a DEXA scan, it’s the best tool for getting a true measure of your body composition. Even if you don’t have access to this tool, tracking your body fat with other methods over time is still valuable for monitoring your health.
The most important part of all of this is focusing on what you can do to optimize your body composition. Engaging in resistance training is the best way to increase muscle mass and bone density. Staying active in any form, whether through yoga, hiking, or walking, can also support your overall health as you age. The goal should always be to improve and maintain your muscle and bone health to ensure a longer, healthier life.
Update from Mark Hyman, on 2024-11-18Source