The Importance of Monitoring Your Body Composition (Instead of Weight or BMI ) Over Time
January 26, 2021
By tracking your body composition, you can measure your progress, catch unwanted changes, and set attainable, time-bound goals.
For more than a century, the Body Mass Index (BMI) has been universally relied upon as a measure of health and wellness. Invented nearly 200 years ago by Belgian scholar Adolphe Quetelet, BMI—calculated by dividing your weight by your height squared—is an outdated, limited metric with critical flaws. While perhaps slightly more useful than looking at scale weight (another flawed measure), BMI does not distinguish between excess fat, muscle, or bone mass, nor does it provide any indication of the distribution of fat within the body.
When it comes to assessing the impact of your fitness, nutritional, or lifestyle changes, there are other, more valuable indicators of progress—first and foremost of which is your body composition. Introduced as a concept in the early 20th century, body composition has been embraced in the last few decades by medical science as one of our most effective measures of body fat and overall health.
Defined simply, your body composition is the total amount of fat, muscle, bone, and water in your body. Body composition analysis goes beyond your weight and the traditional body mass index (BMI) to reveal your body’s proportions of fat mass and lean mass. Fat mass refers to all the different fat in your body, while lean mass refers to your muscles, bones, ligaments, tendons, internal organs—essentially everything in your body that isn’t fat.
Although there are several methods to test body composition, Dual-Energy X-Ray Absorptiometry (DEXA or DXA) scanning remains one of the most detailed techniques (but more on this later).
Why Routine Body Composition Analysis Is Important
Regardless of your health goals and fitness level, it’s wise to keep a close eye on your body composition over time. Here’s why it’s important to get body composition checkups at regularly scheduled intervals:
You can measure your progress. While a single body composition analysis will give you a solid understanding of where you’re starting, monitoring your body composition over time will reveal your progress. By tracking changes in fat and lean mass, you can assess what is working with your current fitness and/or nutritional strategy and make tweaks accordingly.
You can catch unwanted changes. Keeping an eye on your body composition lets you spot unwanted changes, such as unnecessary fat gain, muscle loss, or bone density loss. Through routine body composition checkups, you can catch these negative developments while they are minor. This allows you to make changes to your lifestyle before small, unwanted changes balloon into much larger problems—like chronic illnesses.
You can set attainable, time-bound goals. After embarking on a new fitness and nutrition plan, measuring your body composition will give you a sense of the time it takes for your body to make the changes you want. Armed with information, you’ll be able to set attainable health and weight optimization goals within an appropriate time frame.
How often to test your body composition
As a rule of thumb, it’s a good idea to schedule body composition measurements around three to four times per year and no sooner than once every three months for DEXA scans—though this may vary depending on your goals.
To determine how frequently you should measure your body composition, consider your goals, timeline, and whether you are following a new wellness or nutrition plan. For instance, if you are working to optimize your health by losing body fat, it’s advisable to check your body composition every two to four weeks. After starting a new fitness or nutrition program, it generally takes around four weeks before noticeable changes occur in lean muscle and body fat. On the other hand, if your goals are more long-term—say, to maintain your current body composition—a few times per year should suffice.
However often you test your body composition, it is highly recommended that you stick to the same technique—DEXA scanning or otherwise—when scheduling future body composition measurements to avoid noise in your results.
It’s worth noting that DEXA scans, while very safe, use a low level of radiation. The radiation in a DEXA scan is comparable to the level of exposure you’d experience on a transcontinental flight, so getting a scan a few times a year is fine. Still, DEXA scans are not recommended for pregnant women.
What Your DEXA Body Composition Results Tell You
The results of your body composition analysis will tell you the ratio of body fat to lean mass in your body.
In addition to a breakdown of fat mass versus lean mass, a DEXA scan breaks things down further to reveal how your body composition is distributed in different areas of the body—including your arms, legs, and abdomen. Importantly, DEXA results give a precise measure of the level of unhealthy visceral fat found in your abdominal area. Unlike relatively harmless subcutaneous fat, an excess of visceral or abdominal fat can increase your risk of developing conditions like heart disease or type 2 diabetes.
This method will also give you an accurate reading of your bone mineral content or bone density, revealing how strong your bones are. Note that visceral fat and bone density measurements are unique to DEXA scanning and are not typically included with BOD POD testing or hydrostatic weighing.
How Changes in Your Lifestyle Can Alter Your Body Composition
Maintaining a healthy body composition—or the appropriate balance between fat and muscle for your age, weight, and genetic determinants—can increase your lifespan, reduce your risk of disease, boost your energy, and help you fight off disease.
You can alter your body composition by changing your body’s ratio of fat mass to lean mass—a process sometimes referred to as body recomposition. Body recomposition doesn’t focus on weight loss—you may maintain your current weight or even gain weight as you build muscle mass and shed fat.
Because you're often simultaneously trying to lose fat while gaining muscle, you can’t approach body recomposition like a fad diet. To successfully improve your body composition, follow these science-backed strategies:
Get adequate protein.
Sufficient protein ensures that your body has enough amino acids to recover muscle tissue and maintain lean mass, even when cutting calories.
You can calculate your protein needs quite accurately based on your lean body mass (LBM) and activity level. Here’s how to calculate your daily protein needed in grams based on your activity level:
Sedentary (or generally inactive): Multiply your LBM by 0.5
Light activity (such as cleaning or walking): Multiply your LBM by 0.6
Moderate activity (30 minutes of moderate exercise three times per week): Multiply your LBM by 0.7
Active (One hour of vigorous exercise five times per week): Multiply your LBM by 0.8
Very active (10 to 20 hours of vigorous exercise per week): Multiply your LBM by 0.9
Athlete (more than 20 hours of vigorous exercise per week): Multiply your LBM by 1.0
For example, if your body composition test reveals you have an LBM of 100, your daily protein goal should be between 50 grams and 100 grams, depending on your activity level.
Cut calories cautiously.
Losing fat mass requires you to eat fewer calories than you burn each day. However, cutting calories too dramatically could impair your metabolism and hinder your fat loss. You should never eat fewer calories than your resting metabolic rate (RMR), which is the minimum number of calories you need to perform basic, life-sustaining functions like breathing, cell growth and repair, and blood circulation.
Grow muscle through exercise.
In addition to increasing the number of calories you burn per day, exercise promotes optimal muscle growth. Strength training, in particular, challenges your muscles to grow and become stronger. While every body is unique, strength training for at least 20 to 30 minutes two to three times a week is typically needed to generate results.
Aerobic exercise can also help improve your body composition by reducing fat through calorie-burning. For best results, you should mix moderate-intensity cardio with high-intensity intervals for 200 to 300 minutes a week.
Track changes in your body composition over time.
As we explained above, monitoring your body composition is essential for assessing what is and isn’t working in your current fitness and nutrition plan. By tracking your ratio of fat to lean mass, you can also catch unwanted changes like fat gain or muscle loss. Using the knowledge of how your body composition has responded to different lifestyle changes, you can make informed modifications to your wellness and nutrition strategy.
No matter where you are in your journey towards your health goals, getting precise, in-depth metrics about your body composition is invaluable. Kickstart your journey by scheduling a DEXA scan near you.
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