Your weight is only one part of your health. Two people can weigh the same but have very different levels of health. That’s because the number on the scale doesn’t tell you what your body is made of.

What is body composition?

Body composition is the breakdown of what makes up your body. It includes:  

1. Fat mass
   
   
   1. Essential fat helps your hormones work, keeps you warm, and protects your organs.
   2. Storage fat is extra fat your body keeps for energy.
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2. Fat-Free mass (FFM), also referred to as Lean Body Mass (LBM)
   
   1. This includes your muscles, bones, water, organs, and other tissues

Why Body Composition Matters More Than Weight

Your weight doesn’t show how much is fat or muscle. Two people with the same weight might look and feel completely different.

By measuring body composition, you get a clearer picture of your overall health—especially if you're working on weight loss or fitness goals.

How to Measure Body Composition

There are several ways to measure body composition—some simple, some more high-tech:

• Skinfold Calipers – A manual method using a tool to pinch and measure skin thickness in various parts of the body to estimate body fat.

• Bioelectrical Impedance Analysis (BIA) – A method using a specialized scale or handheld device that sends a small electrical current through the body.  

• DXA (Dual-Energy X-Ray Absorptiometry) – A medical-grade scan often used in bone density testing.

• MRI or CT Scans – Highly accurate but typically used for medical reasons with high cost.

• Hydrostatic Weighing – Involves being submerged in water to assess body density.

• Air Displacement Plethysmography (like the Bod Pod) – Uses air pressure to estimate body fat and fat free mass.

Among these, Bioelectrical Impedance Analysis, or BIA, is one of the most accessible and widely used. BIA testing is available with some home scales, at fitness centers, and in medical offices. The more advanced the machine, the more accurate the results. knownwell offers advanced BIA testing at all of our physical clinic locations.

How to Understand Your Body Composition Results

Body Fat Mass % (or Percent Body Fat):

During weight loss, the primary goal is to reduce body fat while preserving muscle mass and maintaining proper hydration. Reducing fat mass can significantly improve metabolic markers – such as blood sugar, insulin resistance, and lipid panels – and can reduce chronic inflammation.

Here are some general guidelines for an appropriate body fat percentage:

• Men: 10–24%

• Women: 15–29%

Skeletal Muscle Mass:

Keeping muscle matters. Muscle helps you stay strong, move easily, and keep your metabolism (how many calories you burn) higher. Losing too much muscle can make daily tasks harder and lower your quality of life.

Although losing some muscle during weight loss is expected, a simple rule of thumb during weight loss: For every 4 pounds you lose, no more than 1 pound should come from muscle or other lean tissue. (This is sometimes called the “quarter FFM rule.”)

How to Improve Body Composition

Even if your weight stays the same, you can improve your health by changing your body composition by building more muscle and reducing fat.

Two key habits to work toward this is:  

1. Move Your Body
A mix of aerobic exercise (like walking or biking) and strength training is best. Strength training helps you build and maintain muscle, which is the only scientifically proven way to boost your metabolism. Strength training can include free weights, weight machines, resistance bands, or creating resistance against your own body weight (think push-ups, or squats). Aim to train all major muscle groups at least twice per week. There isn’t one size fits all when it comes to fitness regimens. We recommend checking with your knownwell clinician to find a routine that it is appropriate for your individual health needs

2. Prioritize Protein
Protein is essential for building and preserving muscle. Include a high-quality protein source—like chicken, fish, tofu, eggs, Greek yogurt, beans, or lentils—with every meal. A knownwell Registered Dietitian can help tailor your protein needs and offer creative strategies to incorporate more protein into your meal plan.

The Bottom Line: Body Composition Is Key to Better Health

Improving your body composition—not just your weight—can have a powerful impact on your health. Focus on lifestyle habits that may result in keeping muscle while lowering extra body fat. If you want to learn more about your own numbers, talk to your knownwell healthcare provider or Registered Dietitian about BIA testing and a personalized plan.

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