What Is Body Composition?

Most of us know how tall we are and about how much we weigh. But, there’s a lot more going on inside our bodies than just the number on a bathroom scale–so let’s get into it! Read on to learn all about body composition: what it is, how to measure it, how to improve it, and why it’s so important.

What is body composition?

Inside our bodies, we have all kinds of things that take up space: muscles, organs, fat, bones, tissues, and more. Each of these components impacts our health–and adds to our weight in different amounts. While weight only tells you how heavy you are, body composition gives a more complete picture of what that weight is actually made of.

So, what is body composition exactly? Well, body composition refers to the amount of fat and lean mass that make up the body. Let’s break that down.

• Body fat: When looking at body composition, it’s important to understand the difference between essential fat and excess fat. Essential fat protects your organs, regulates your energy, and is needed for processes like reproduction (1). Excess fat comes in a few forms, with visceral fat being the most problematic. Having too much visceral fat is linked to an increased risk of health conditions like heart disease, certain cancers, and diabetes (2).
• Lean mass: Also called fat-free mass, your lean mass is made up of everything that’s not fat in your body. This includes your muscles, bones, organs, and water. Muscle is heavier than fat and there are a few different types of muscles in our bodies. Skeletal muscles are the ones we can actively control–and about 40 percent of our total weight comes from them (3)!

When you understand your body composition, you know how much of your weight comes from fat and how much comes from lean mass. Why is this measurement useful? Well, because two people with the same height and weight can have completely different amounts of body fat and muscle mass! Knowing your body composition can give you more insight into your health, fitness level, and progress toward wellness goals than weight alone.

The difference between body composition and BMI

Okay, so we’ve covered that body composition can give you a better understanding of your health than just your weight. But, how does body composition compare with body mass index (BMI)?

Health professionals have used BMI for years to assess and track people’s health. The Centers for Disease Control and Prevention (CDC) uses the following BMI categories for adults (5):

• Underweight: Less than 18.5
• Healthy weight: 18.5 to 24.5
• Overweight: 25 to 29.9
• Obese: 30 and above

Unlike body composition, BMI doesn’t directly deal with the amount of fat in your body. BMI is just a ratio of your height and weight. This makes BMI quick and easy to calculate, but it comes with some limitations.

Having a high BMI can mean you’re at a greater risk of health problems. But, it isn't always accurate because BMI doesn’t take into account differences like age, sex, and fat distribution (6). And, because muscle weighs more than fat, you might inaccurately creep into an unhealthy BMI category if you have a lot of muscle mass.

So, while BMI has its limitations, it remains a key metric in most medication studies to produce standardized results that guide medical practice. Clinicians still rely on BMI in specific scenarios–like prescriptive weight care and the birth control patch–to ensure safe, effective, and evidence-based care. Body composition is a more individualized measure of overall health, but BMI is still needed and relevant.

How to measure body composition

Measuring your body composition is more complicated than weighing yourself or calculating your BMI. But, tracking your body composition is super important–especially when you’re starting a new exercise program!

Activities like strength training help you build muscle. And this new muscle mass can make your weight stay the same or even go up, even though you’re headed in a healthy direction. Focusing only on your body weight can be discouraging and doesn’t offer a complete picture of your progress. Instead, take progress pictures and monitor changes in your body composition!

Ways to measure body composition include:

• At-home scales: Smart scales estimate your body fat percentage by sending an electrical signal through your body. While these at-home scales are convenient, they aren’t very accurate and shouldn't replace a more professional assessment (7).
• InBody machines: InBody machines are available at some gyms and estimate body fat in a similar method to at-home scales. They’re more accurate than at-home scales, but results can vary from machine to machine. For consistent tracking, use the same machine and drink the same amount of water beforehand (8). -Skinfold measurements: For this method, you use calipers to measure subcutaneous fat–the fat under your skin–in a few different areas of the body. Estimating body fat percentage with skinfold measurements is simple and accurate when done correctly by a professional (9).
• DEXA scans: Dual-energy X-ray absorptiometry (DEXA) scans provide detailed information about muscle mass, fat distribution, and bone density. While they’re not as easy or convenient as other options, DEXA scans are an accurate way to measure body composition for almost all body types (10).
• Progress pictures and measurements: They’re not high-tech, but they still work! Taking progress pictures and tracking your waist, hip, and other measurements can help you monitor changes in body composition. This is especially important if your weight is staying the same due to muscle gains.

Regardless of how you measure your body composition, things like hydration, how much you’ve eaten, and time of day can impact your results. Try to take your measurements under consistent conditions–like in the morning before exercising or eating–to accurately track your progress.

What factors influence body composition?

A lot of factors can influence your body composition–some you can control, and some you can’t. So, while it’s important to understand everything that affects your body composition, the most useful approach is to focus on what you can control. With that in mind, things that impact your body composition include:

• Sex: People assigned female at birth naturally have a higher percentage of body fat, with more fat distributed around the hips and thighs. But, great news: this fat distribution is associated with a lower risk of heart disease and type 2 diabetes (11)!
• Age: As we get older, we naturally lose muscle mass. This increases our risk of osteoporosis and can lead to an increase in body fat (3). Resistance training is one of the best ways to combat these changes.
• Hormones: Hormonal changes during menopause can cause a significant change in body composition, specifically gaining visceral fat (12). Similarly, hormonal disorders like polycystic ovarian syndrome (PCOS) can make it easier to gain body fat and harder to lose it (13).
• Genetics: Though environmental factors like diet and exercise are important, studies show that genes have an impact on body shape and where you carry your body fat (14).
• Lifestyle factors: This is the first factor under our control, making it an important one! Lifestyle factors like diet, exercise, smoking, and alcohol consumption have a major impact on your body composition (15). Besides that, not getting enough sleep and chronic stress are also associated with a higher body fat percentage (16, 17).

How to improve body composition

Remember: your body composition is unique to you. And if you’re looking to change your body composition–by increasing muscle mass, reducing fat, or both–consulting with a healthcare professional can help you understand how to move forward. With all that in mind, let’s look at some safe and effective ways to improve your body composition.

Increase your physical activity

To lose weight, the basic idea is to burn more calories than you take in. One great way to do this is by getting more exercise. Effective forms of exercise include:

• Get more steps: Increasing the number of steps you take each day is a great way to track how much movement you’re getting outside of planned exercise. A fitness tracker or smartwatch isn’t necessary–just keeping your phone in your pocket will count your steps throughout the day!
• Build muscle mass: Building muscle mass through resistance training–aka training with weights–is an effective way to lose weight and gain fitness at any age. When paired with a caloric deficit, resistance training has been shown to be the most effective way to lose body fat (18). Increasing your muscle mass also improves bone density, making it essential to combating osteoporosis as we age (19).
• Try a HIIT class: If resistance training isn’t your fave, high-intensity interval training (HIIT) is also an effective way to build lean muscle mass and lose fat (20).

Eat a balanced diet

It might be cliche, but eating a well-balanced diet is a great way to support healthy changes in your body composition. This includes focusing on eating fruit, vegetables, whole grains, and healthy fats–while also making sure you’re getting enough fiber and protein.

Eating enough protein can help you feel fuller after meals and support weight loss efforts. Aim to eat between 1.2 and 1.6 grams of protein per kilo of body weight each day (21)!

If you’re supporting your weight loss journey with GLP-1 medications like Wegovy, it’s especially important to make sure the food you’re eating is nutritious and not highly processed. GLP-1s can reduce your appetite meaning it’s important to make each of your meals count! This will also help you build healthy habits so you can maintain your weight loss progress if you stop taking the medication.

Behavioral changes

When you’re changing your body composition, small behavioral changes can help you stick to your plans and reach your goals. For starters, getting enough sleep and managing your stress levels is essential for both your mental and physical health. Joining support groups, journalling, and tracking your exercise and nutrition are other ways to help keep you motivated on this journey.

Tracking your progress

If you’re busy working to change your body composition, know that how you feel is sooo much more important than any measurement or number on a scale. Tracking your progress with multiple tools, paying attention to how you feel, and staying consistent is the name of the body composition game. Remember that every step is totally worth celebrating–and if you need any support along the way, Wisp is here to help.

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