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Writer's pictureHarry T.

Body Fat Percentage vs. BMI in Personal Training

Updated: Feb 27


A woman measuring her waist with a tape measure


Are you a Personal Trainer who wants to help your clients lose body fat and increase lean mass? How should you measure body fat - BMI or Body Fat Percentage? What is the most accessible, comfortable, and affordable way to keep track of progress? In this guide, we cover all these questions and more!


In the realm of personal training, understanding and assessing body composition is paramount to crafting effective fitness plans for clients. Two commonly used metrics for gauging body composition are Body Fat Percentage (BFP) and Body Mass Index (BMI). While both play crucial roles in evaluating overall health, they serve distinct purposes and offer different insights.


In this comprehensive guide, we'll delve into the intricate details of Body Fat Percentage vs BMI, exploring their differences, strengths, and limitations, to equip personal trainers with the knowledge needed to tailor fitness programs with precision.


What is Body Fat Percentage: The Real Measure of Composition vs Body Mass Index (BMI)


Body Fat Percentage (BFP), as the name suggests, measures the proportion of fat in the body relative to the total body weight. Unlike BMI, which relies solely on height and weight, BFP provides a more accurate depiction of body composition by distinguishing between lean mass and fat mass.


The Importance of Body Fat Percentage in Personal Training

1. Precision in Composition Analysis:

  • While BMI categorizes individuals into broad weight categories, BFP offers a more nuanced analysis, considering the distribution of weight in terms of fat and lean mass.

  • Personal trainers can use BFP to identify areas of improvement, guiding clients towards a healthier balance between fat and muscle.

2. Targeted Goal Setting:

  • BFP allows for specific goal setting by targeting the reduction of fat mass while preserving or increasing lean muscle mass.

  • Personal trainers can tailor workout and nutrition plans to achieve desired BFP goals, ensuring clients achieve a balanced and healthy body composition.

3. Better Understanding of Health Risks:

  • Elevated body fat percentages are associated with an increased risk of various health issues, such as heart disease, diabetes, and joint problems.

  • Personal trainers can use BFP as a tool to educate clients about the importance of maintaining a healthy body composition for overall well-being.


How to calculate Body Fat Percentage

There are various methods for measuring BFP, each with its own level of accuracy and practicality. Some common techniques include skinfold calipers, bioelectrical impedance analysis (BIA), dual-energy x-ray absorptiometry (DEXA), and hydrostatic weighing. Personal trainers can choose the method that aligns with their clients' preferences and resources, taking into account factors such as cost, accessibility, and precision.


DEXA scans and hydrostatic weighing can be difficult find everywhere and expensive to do frequently. Here's how you can track your clients' progress in terms of body fat percentage.


Three easy ways to measure your clients' Body Fat Percentage


A woman using skin calipers to measure body fat

  1. Bioelectrical impedance analysis (BIA): Chances are you can find a BIA machine at the gym you train with. Most gyms such as Gold's Gym include monthly scans for their customers as part of their membership. These machines store historical data as well which is great for keeping a track of your client's progress.

  2. Skinfold Calipers: While these seem a bit intense to use on your clients, they are fairly accurate. You can measure your clients directly (if they are comfortable with you doing so) or teach them on how to do so. Keep a store of their measurements on an app like EZbook and record their monthly progress. Skin calipers are quite affordable and accessible on Amazon. How to use skinfold calipers to measure body fat percentage with formula

  3. Tape measurements: While this method won't give you the most accurate indication of body fat percentage, it is a great way to measure fat loss progress and it's something your clients can do at home, frequently, with little to no training.


Track your clients' Body Fat Loss progress on the free EZbook App


Use EZbook to track sessions, workout logs, client progress, and more! This is a free app made for Personal Trainers and Fitness Coaches who want to scale their business.

The best part? Copy your previous progress template and never retype again. Share with your clients with an easy view-only link.




EZbook app helps you log workouts and client progress
EZbook app helps you log workouts and client progress


What is Body Mass Index or BMI: A Broad Brushstroke Approach

BMI or Body Mass Index, on the other hand, is a quick and straightforward metric calculated by dividing an individual's weight in kilograms by the square of their height in meters. Unlike Body Fat Percentage, it is not accurate and often requires double clicking to understand real progress. While widely used and easily calculated, BMI has significant limitations when it comes to assessing individual health and fitness.


The Drawbacks of Relying Solely on BMI

1. Neglects Body Composition:

  • BMI categorizes individuals based on weight and height alone, ignoring the distribution of that weight in terms of fat and muscle.

  • Personal trainers may encounter scenarios where clients with a high BMI are actually muscular and fit, while those with a lower BMI may have elevated body fat percentages.

2. Doesn't Differentiate Between Fat and Muscle:

  • Athletes and individuals with higher muscle mass may fall into overweight or obese BMI categories, even though their body fat percentages are low.

  • Personal trainers need to be cautious when using BMI to assess fitness levels, especially in clients with significant muscle mass.

3. Inaccuracy in Special Populations:

  • BMI might not be suitable for certain populations, such as the elderly or athletes, as it doesn't account for factors like age, gender, or muscle distribution.

  • Personal trainers working with diverse client groups must be aware of BMI's limitations and complement it with more accurate measures like BFP.


Finding the Right Balance: Should you use both BMI and BFP?

We recommend using BFP as the best way to calculate fat loss progress. BMI can cause confusion if used incorrectly. For instance, if someone has a large weight due to a lot of muscle mass and a small build, he/she may be flagged for high BMI (which is concluded as unhealthy) but in reality their body fat could be very low.


While both Body Fat Percentage and BMI have their merits and drawbacks, a comprehensive approach to body composition assessment can involve both metrics. By combining BFP and BMI, personal trainers can gain a more holistic understanding of their clients' health and fitness levels. Here's how you can use both if you must use both:


1. Initial Assessment with BMI:

  • BMI can serve as a quick and accessible initial screening tool to identify potential weight-related health risks.

  • Personal trainers can use BMI as a starting point for discussions with clients, emphasizing the need for a more in-depth analysis of body composition through BFP.

2. Detailed Analysis with BFP:

  • Once BMI highlights potential concerns, personal trainers can conduct a more detailed assessment using BFP to differentiate between fat and lean mass.

  • BFP provides the necessary details to create tailored fitness plans that address specific areas of improvement.

3. Client Education and Goal Setting:

  • Personal trainers play a crucial role in educating clients about the limitations of BMI and the importance of maintaining a healthy body composition.

  • By setting realistic goals based on both BMI and BFP, trainers empower clients to achieve balanced and sustainable results.

4. Periodic Monitoring and Adjustments:

  • Regular reassessment using both BMI and BFP allows personal trainers to track progress accurately and make necessary adjustments to fitness and nutrition plans.

  • This dynamic approach ensures that clients are on the right track to achieving their desired body composition and overall health.


Here are other considerations to keep in mind

1. Client Preferences and Comfort:

  • Some clients may prefer non-invasive methods for assessing body composition, while others may opt for more precise but intrusive techniques.

  • Personal trainers should discuss available options with clients, considering their preferences, comfort levels, and budget constraints.

2. Integration of Technology:

  • Technological advancements have introduced smart scales and devices that claim to measure both BMI and BFP accurately.

  • Personal trainers should stay informed about the reliability of such technologies and guide clients in choosing tools that align with their accuracy and convenience requirements.

3. Cultural Sensitivity:

  • Cultural perceptions of body image and fitness can influence how clients interpret BMI and BFP results.

  • Personal trainers must approach discussions about body composition with cultural sensitivity, fostering a supportive and understanding environment.


EZbook helps you track client workouts, sessions, payments and more in 2-clicks! Download Today.

EZbook is made for Personal Trainers and Fitness Coaches who want to scale their business by automating busywork and generating more leads. If you need help or would like to learn more about EZbook, write to us at helloezbook@gmail.com. We reply as soon as possible!


Download EZbook and try for free. No Credit Card required.




In the dynamic world of personal training, achieving optimal health and fitness requires a nuanced understanding of body composition. While BMI provides a quick snapshot of weight-related health risks, Body Fat Percentage offers a more detailed analysis, taking into account the distribution of fat and lean mass. Personal trainers equipped with the knowledge of both metrics can guide their clients toward balanced and sustainable fitness goals. By combining the broad strokes of BMI with the precision of BFP, trainers can create tailored fitness plans that address individual needs, empowering clients to embark on a journey of holistic well-being. As the fitness industry continues to evolve, personal trainers who embrace this comprehensive approach to body composition assessment will undoubtedly stand out as leaders in promoting health and fitness for all.

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