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5 Alternatives To Body Mass Index (BMI)

By James Redden| Last update: 18 July 2023

BMI is, at it's most basic, a calculation of the relationship between your height and weight. The higher your Body Mass Index the more overweight you are.

Many doctors and healthcare professionals use BMI as a guide when they are assessing the general health of patients. However, the method, which has been in use since the 1840's, has some weaknesses.

The first problem is that it doesn't give a real estimate for the percentage of body fat. Another problem is that men and women can have the same percentage of fat but different BMI readings. Finally, carrying a lot of muscle can give an inaccurate BMI reading.

In 2013, Nick Trefethen, a member of Oxford University's Mathematical Institute, came up with an alternative and improved formula for BMI. Nick explained that the problem with the current BMI formula is that humans do not grow equally in all three dimensions.

Confused about what to think? Don't panic! There are alternatives to BMI. In fact, combining one or more of the methods shown below will give you a far more accurate indication of how much body fat you are carrying.

Let's have a quick at some of the alternatives available to you...

Body Adiposity Index

BAI is unlike BMI as it does not use your weight in the calculation. In order to work out your percentage body fat, BAI multiplies your hip circumference by your height. Although clinical studies have not shown any proof, it is widely believed that Body Adiposity Index is more accurate than BMI as the resulting figures are approximate. BAI is useful in areas where scales may not be available, such as the jungle or desert.

Waist Circumference Measurement

One of the most effective alternatives to BMI is the old fashioned tape measure. By measuring the natural waist you can get a good indication of the amount of abdominal fat you are carrying. Knowing the circumference of your waist can help determine your risk of getting heart disease and other medical conditions. According to physicians, the following figures indicate individuals in the 'at risk' group: women with a waist circumference of 35 inches and over and men with a waist circumference of 40 inches and over.

Waist-to-Hip Ratio

The waist-to-hip ratio is not only an excellent way of calculating how much excess weight you are carrying, it can also be used to indicate susceptibility to a number of health issues, including high blood pressure, heart disease and diabetes. You can read more about waist-to-hip ratio here. We also have a waist-to-hip calculator here.

How do you calculate your waist-to-hip ratio?

Using a tape measure, take a reading from your natural waist line and the widest part of your hips. Now divide the circumference of your waist by your hip circumference measurement. Once you've done that, compare to our results chart below.

Illustration of waist to hip ratio measurements
How to measure waist-to-hip measurements.
Image credit: Mikael Häggström.

Waist-to-hip ratio results chart

The figures in the waist-to-hip chart below are based upon the standards set by the German Society for Sports Medicine and Prevention (DGSP).

< 0.90< 0.80 normal weight
0.90 to 0.990.80 to 0.84over-weight

Note that the World Health Organisation deems that abdominal obesity is represented by a waist–hip ratio above 0.90 for males and above 0.85 for females.

Hydrostatic Weighing

Contrary to popular belief, hydrostatic weighing is not an ineffective way of calculating body fat. The weighing process takes place underwater on a chair that is placed on a zeroed out set of scales. You then sit on the chair before exhaling all the air from you lungs and then placing your head underwater. Once the scales stabilise, your weight is taken. The resulting figure is then passed through a series of formulas which, ultimately, produces a body-fat reading.

Body Fat Measuring

Probably the simplest way to calculate your body fat is by using a special set of callipers. Skin and fat measurements are taken from the waist, shoulder blade, biceps and triceps. The resulting readings, in millimeters, are added up to produce a single figure. The figure is then plotted against a chart that takes the patient's sex, age and measurement into consideration to determine the body-fat percentage figure. The higher the body fat, the higher your risk of suffering from obesity-related conditions.

Final Thoughts

Should you wish to calculate your BMI as part of a series of measurements for overall health assessment, give our BMI calculator a try. As always, it's recommended that you speak to a Doctor or health professional for advice and guidance if you are concerned about your weight.

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