BMI, waist circumference, body fat … what does it all mean?

In the battle to shape up, the scale often becomes the enemy. It is the quickest and easiest way to receive feedback on whether your diet and workout regimen are working or not. However, the scale only tells you a small part of the story. For example, you can lose fat and gain muscle, yet still stay at the same weight. Without tracking other measurements, such as body composition and waist circumference, it is easy to get discouraged when the number on the scale doesn’t reflect your hard work.

Let’s take a deeper look at the other ways to track success in your weight management journey. It is very important to know that each of these indicators have room for error, and you should work with a qualified professional when taking measurements.

Body Mass Index (BMI): Your BMI is a measurement based on your weight to height ratio. A high BMI can indicate high body fat. However, since it can’t distinguish muscle from fat, this may be a poor marker of changes in body composition. As an overall marker of health, BMI may provide a false sense of security to individuals with low muscle mass, such as the sedentary or elderly, or misclassify those with large muscle mass as overweight or obese.

BMI is inexpensive and commonly used by physicians to assess individual disease risk, but it has many drawbacks. It does not take into account several factors including muscle mass and frame size, and is particularly inaccurate for people who are very fit and those with high body fat, but low muscle mass, like the elderly. High muscle mass may classify athletes as overweight or obese, despite very low body fat percentages.

BMI is calculated by dividing weight (kg) by height (m) squared. For adults 20 years old and older; below 18.5 BMI is considered underweight; 18.5-24.9 BMI is considered normal or health weight; 25.0-29.9 BMI is considered overweight; and 30.0 and above is considered obese.1

Waist Circumference: Aside from your weight, body fat distribution is an important risk factor for obesity-related disease. Excess abdominal fat is associated with an increased risk of diseases, such as diabetes and cardiovascular disease. Since accurate measures of abdominal fat is complicated and expensive, waist circumference is often used.2 you may be at greater risk of chronic disease if you are:

  • a man who has a waist circumference greater than 40 inches2
  • a non-pregnant women whose waist circumference is more than 35 inches2

Measuring your waist circumference (waistline) is simple: using a tape measure around your abdomen, just above your hip bones, ensure that the tape is snug, but not tight. Relax, exhale and measure your waist. You can also ask a personal trainer or your physician to help ensure you get an accurate measurement. Waist circumference is useful to monitor change that may not get noticed if fat is lost and lean mass is gained. When combined with weight, waist circumference can be a decent tool for tracking change in body composition, but is not as good as body fat, as we will discuss next.

Body Fat: Body fat percentage (BFP) is a measurement of fat in your body, as opposed to lean body mass that includes muscle, organs, and bone. Percent of body fat is calculated by dividing total weight of lean mass by total body weight and multiplying it by 100. It is primarily useful in measuring aesthetic changes, such as muscle gain and fat loss. It is important to note that too little body fat can cause serious health complications and women require higher body fat to be healthy.4  Therefore, a woman should not compare her physique to a man’s. There are several ways to measure body fat including: 5

  • Skin Calipers: measure folds of skin and fat taken from sites on the body. These are then entered into an equation to estimate total body fat.
  • Bioelectric impedance: measures strength and speed of an electrical signal sent through the body. It then takes this measurement and factors it with height, weight, and gender to predict body fat.
  • Hydrostatic weighing: compares someone’s normal weight outside of water to their weight underwater.
  • DEXA (dual-energy x-ray absorptiometry) scan: provides readings for bone mineral density, lean body mass and fat mass.

These methods do have room for error. Work with your physician and/or fitness professional to determine where your numbers are and a sensible workout and diet plan to help you achieve your goals.

This blog and its contents are provided for nutrition information purposes only and does not constitute medical advice. The information and topics may not apply to every individual and sometimes are based on alternative healthy philosophies rather than traditional scientific views. Always seek the advice of a qualified health provider with any health or nutrition concerns you may have. The information in this article is not intended to promote any specific product, or for the prevention or treatment of any disease and should not be a substitution any medical needs or advice.

 1(2017). Retrieved 2018, from https://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html

2(2018). Retrieved 2018, from https://www.nhlbi.nih.gov/health-topics/overweight-and-obesity

3Bower, J. K., Meadows, R. J., Foster, M. C., Foraker, R. E., & Shoben, A. B. (2017). The Association of Percent Body Fat and Lean Mass With HbA1c in US Adults. Journal of Endocrine Society, 1(6): 600-608.

4(2018). Retrieved 2018, from http://www.freebodyfatcalculator.org/body-fat-percentage-chart/

5(2018). Retrieved 2018, from https://dailyburn.com/life/health/how-to-measure-body-fat-percentage/

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