Many people dread stepping onto the bathroom scale.

It can be very frustrating to exercise and eat a healthy diet only to see the number on the scale stay the same.

However, just because your body weight isn’t changing doesn’t mean that your hard work isn’t paying off. Especially if you are exercising, your body composition may be improving.

This article will explain what your body composition is and how to improve it, based on science.

What Is Body Composition?

While the scale will tell you how much you weigh, it doesn’t tell you what your body is made of.

Body composition refers to everything in your body, split up into different compartments. Two compartments are commonly used: fat mass and fat-free mass (1).

Fat mass refers to all the fat tissue in your body. Fat-free mass is everything else, including muscle, organs, bone and fluid.

If both change at once, you might not see any changes in body weight.

For example, if you start exercising, you may gain two pounds of muscle in the first month. At the same time, you may lose two pounds of fat due to burning more calories through exercise or changes in your diet.

Since your fat-free mass increased by the same amount as your fat mass decreased, your body weight won’t change.

If you focus on the number on the scale, you may become discouraged or frustrated because your program “isn’t working.”

This is one example of why knowing your body composition is much more useful than knowing your body weight.

Summary: Knowing your body composition is more informative than focusing on your body weight, since you can measure both fat mass and fat-free mass.

How Can You Assess It?

There are many methods to assess your body composition. Some are very simple and easy to use, while others are advanced and complicated.

The most accurate methods are usually expensive and only used in research or medical centers.

However, there are some simple methods you can use at home to give you an idea about whether your body composition is improving.

Tracking Body Circumference

One technique is tracking the circumference of different body parts (2).

You may have had your waist circumference measured with a flexible tape measure at the doctor’s office.

At home, you can also track the circumference of other body parts, such as the hips, arms, legs or chest.

You can make these measurements using a cheap, flexible tape measure.

While a change in circumference doesn’t exactly tell you if your fat mass or fat-free mass is changing, it can give you an idea.

For example, decreases in waist circumference are typically a sign that you are losing belly fat (3).

Gram for gram, fat takes up more space than muscle. This means your waist circumference may decrease when you lose fat, even if your weight doesn’t change.

If you’re exercising with weights, increases in arm circumference may mean that you are gaining muscle in your arms (4).

Of course, it is very important to measure the same way each time so that you get more accurate results.

Taking Progress Pictures

Progress pictures are another popular way to get a big picture look at your body composition.

It is often difficult to notice changes in your body from one day to the next.

However, taking pictures of your body every few weeks or months can be one way to assess how your body is changing.

This doesn’t give you exact information, but it can give you a general idea of differences in your size and shape.

Devices That Measure Body Composition

In addition to these simple methods, there are devices you can buy that measure body composition.

Many of these devices use a technology called bioelectrical impedance analysis (BIA).

BIA sends small electrical currents through your body to see how much your body resists the current. This information is used to predict your body fat percentage (5).

While it is nice to see an actual number for your body fat percentage, many of these devices aren’t very accurate.

In fact, research has shown that the common handheld BIA unit underestimates body fat percentage by 8–10%, compared to more accurate research tools (6).

What’s more, factors like food and water intake before using these devices can make the results inaccurate (7, 8).

If you do choose to use a BIA device, be sure to use it in the morning before you eat or drink anything (7).

Summary: There are various ways to measure your body composition. Simple ways include tracking the circumference of body parts and taking progress pictures. You can also buy tools that measure your body fat percentage, but they are often inaccurate.

How to Improve Your Body Composition

Your body composition is made up of fat mass and fat-free mass.

You can improve it by decreasing body fat, increasing muscle or both.

Any of these changes will lead to a decrease in your body fat percentage, which is viewed as a single number that describes your body composition.

Most people know that diet and exercise can affect body weight and body composition.

However, their impact on body composition isn’t always simple.

Nonetheless, a good place to start is with some basic principles of nutrition and physical activity.


First, consider the number of calories you are eating.

Although they aren’t the only thing that matters, calories are one of the most important factors to consider (9).

In simple terms, if you consistently eat more calories than your body uses, you will gain weight — typically as fat. Likewise, if you consistently eat fewer calories than your body uses, you will lose weight.

It can also be helpful to think about the types of food you tend to overeat.

Often, they are processed foods, such as ice cream, pizza and chips, that are highly rewarding to the brain (10).

These foods contain many calories and don’t usually keep you satisfied. This is partly due to their low protein and fiber content.

After considering how many calories you eat, think about whether you are eating enough protein and fiber.

Protein is important for everyone, but you may need more if you are active or trying to gain muscle or lose fat (11).

It is more satisfying than carbs or fat, and your body also burns more calories processing protein than these other nutrients (11, 12).

Fiber also has several health benefits and can increase the feelings of fullness and satisfaction after eating (13, 14).

It can be obtained from a variety of plant-based foods, including beans, whole grains, nuts and vegetables (15).

For adults up to age 50, it is recommended that men consume 38 grams of fiber per day, while women are advised to eat 25 grams per day (16).

Incredibly, less than 5% of most age groups in the United States consume enough fiber (17).

Keeping your calories, protein and fiber in check is a good place to start if you want to improve your body composition and health.

Physical Activity and Exercise

Physical activity and exercise are other crucial components for improving body composition.

They not only increase the calories you use, but they are also necessary for optimal muscle growth.

Since body composition can be improved by decreasing fat mass or increasing muscle mass, this is an important point.

Your muscles need to be challenged by exercise, particularly weight training, to grow and get stronger (18).

However, many types of exercise can potentially help with fat loss (19).

The American College of Sports Medicine states that 150–250 minutes of exercise per week may lead to a small amount of weight loss (20).

If you exercise 5 days per week, this comes out to 30–50 minutes per day, though they recommend 250 minutes per week or more to promote significant weight loss (20).

While these recommendations focus on body weight, it is important to remember that some forms of exercise will build muscle while you are losing fat.

This is another example of why thinking about your body composition, rather than just body weight, is a good idea.

Other Factors

Additional factors beyond nutrition and exercise may affect body composition.

There is some evidence that people who have poorer sleep quality have worse body composition than those with good sleep quality (21).

However, it isn’t clear if good sleep improves your body composition or if having a better body composition improves your sleep (22).

Regardless, it is a good idea to consider whether your sleep habits can be improved.

Alcohol consumption is another factor that may affect body composition. Since alcohol contains calories, it can contribute to excess calorie intake and fat gain (23).

Some research has also shown that individuals who consume a lot of alcohol are more likely to be obese (24).

Additionally, some factors that affect body composition cannot be changed. For example, both age and genetics impact body composition.

However, since you cannot control these factors, it is probably best to focus on what you can control, like nutrition, exercise and sleep.

Summary: Nutrition and exercise are critical for improving body composition. Keeping your calories, fiber and protein in check is a good first step. All exercise can help with fat loss, but weight training is the best way to increase muscle mass.

The Bottom Line

Stepping on the scale will only tell you how much you weigh.

You can get a more accurate picture by taking into account your body composition, or your fat mass and muscle mass.

Two simple ways to track your body composition over time include measuring the circumference of different body parts and taking progress pictures at regular intervals.

There are also devices you can buy to track your body composition, but many are inaccurate.

Your body composition is affected by your nutritional habits, exercise, sleep and other factors. For this reason, improving it can sometimes feel complicated.

However, focusing on some of the basic concepts covered in this article can get you started in the right direction.