What is the Difference Between BMI and Body Fat Percentage

The main difference between BMI and body fat percentage is that BMI or body mass index is the weight to height ratio whereas body fat percentage (BF%) is the percentage of total fat divided by the weight. 

BMI and body fat percentage are the two measurements of health and fitness. Both types of measurements help to monitor weight loss as well as fitness progress. Furthermore, a BMI of 25 or higher is considered overweight and, the normal body fat percentage should be between 25-31% for women and 18-25% for men.

Key Areas Covered

1. What is BMI
     – Definition, Measurement, Importance
2. What is Body Fat Percentage
     – Definition, Measurement, Importance
3. What are the Similarities Between BMI and Body Fat Percentage
     – Outline of Common Features
4. What is the Difference Between BMI and Body Fat Percentage
     – Comparison of Key Differences

Key Terms

Body Composition, Body Fat Percentage (BF %), Body Mass Index (BMI), Obesity, Overweight

What is BMI

BMI (body mass index) is the ratio between the body weight and height. We can obtain the value of MBI by dividing the body weight by the square of the body height. Therefore, the universal unit of BMI is kg/m2. The National Institute of Health (NIH) defines three conditions by the use of BMI: normal weight, overweight, and obesity. The BMI value for the normal weight has to be less than 25 kg/m2. Moreover, the BMI values for overweight conditions lay between 25-29 kg/m2 while the BMI value for the obesity conditions is more than or equal to 30 kg/m2. The difference of weight in individuals with the same height is due to the variable amount of fat they have.

Figure 1: Body Mass Index

Some experts believe that the use of the BMI value is more accurate to determine the effect of weight loss on health. Also, BMI serves as an indicator of the health status of an individual and risk for diseases in most recent medical studies. Furthermore, BMI can predict the risk for high blood pressure, diabetes, heart disease, and other serious illnesses.

What is Body Fat Percentage

Body fat percentage (BF %) is the percentage of the value obtained by dividing the total fat by the body weight. It helps to determine the composition of the body. For example, if the body fat percentage of a particular individual whose body weight is 100 kg is 20%, the weight of the total fat in his body is 20 kg. Meanwhile, the remaining weight, which is 80 kg, is the lean mass of bones, muscles, organs, soft tissue, etc. Thus, this shows that the body fat percentage can vary with the loss or gain of fat as well as the loss or gain of muscles.

Figure 2: Mean Percentage Body Fat Percentage by Age Group and Sex

Moreover, the body fat percentage of men and women are also different. BF % is always less in men than in women. Therefore, while measuring BF % by the skinfold method, in men, abdomen, thigh, and chest are measured by a calliper, and in women, the thigh, hip, and triceps are measured. Since the body fat percentage gives the body compositions, it is always considered as a better measurement in comparison to the BMI.

Similarities Between BMI and Body Fat Percentage

• BMI and body fat percentage are two measurements of health and fitness.
• Both help to monitor weight loss along with the fitness progress.
• Moreover, both help to distinguish health risks associated with our body.

Difference Between BMI and Body Fat Percentage

Definition

BMI (body mass index) refers to a number that reflects body weight adjusted for height while body fat percentage refers to a measure of fitness level. Body fat percentage directly calculates a person’s relative body composition without considering the height or weight. Thus, this is the main difference between BMI and body fat percentage.

Parameters

The two parameters involved in the measurement of BMI are the weight and the height while body fat percentage depends on both the amount of fat and muscle mass.

Complexity

Another difference between BMI and body fat percentage is that BMI is a simple measurement while body fat percentage is a more complex measurement.

Reference Values

There is also a difference between BMI and body fat percentage in reference values. BMI value for the normal weight condition has to be less than 25 kg/m2 while the normal body fat percentage should be between 25-31% for women and 18-25% for men.

Importance

Furthermore, BMI is important in distinguishing between the normal weight, overweight, and obesity while body fat percentage provides a detailed estimate about the body composition.

Detailedness

BMI gives a less detailed measurement while body fat percentage gives a more detailed measurement. Hence, this is another difference between BMI and body fat percentage.

Cost

One other difference between BMI and body fat percentage is that BMI is the least expensive and easiest way to measure fitness while body fat percentage is difficult to measure.

Conclusion

BMI or body mass index is the ratio between the weight and the height of an individual. It helps to distinguish between normal weight, overweight, and obesity. In contrast, body fat percentage is the percentage of the value obtained from the total fat divided by the body weight. It gives the total amount of fat in the body in comparison to muscle mass. Therefore, the body fat percentage gives a more detailed measurement when compared to BMI. Thus, the main difference between BMI and body fat percentage is the type of measurement and its importance.

References:

1. Ranasinghe, Chathuranga et al. “Relationship between Body Mass Index (BMI) and body fat percentage, estimated by bioelectrical impedance, in a group of Sri Lankan adults: a cross sectional study” BMC public health vol. 13 797. 3 Sep. 2013, doi:10.1186/1471-2458-13-797
2. Scott, Jennifer R., and Richard N. Fogoros. “Body Composition and Body Fat Percentage.” Verywell Fit, Verywellfit, Available Here

Image Courtesy:

1. “Obesity & BMI” By BruceBlaus – Own work (CC BY-SA 4.0) via Commons Wikimedia  
2. “Mean Percentage Body Fat 1999-2004” By US Government official site – CDC –  (Public Domain) via Commons Wikimedia  

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