What is BMI?
The body mass index (BMI) is a very simple method you can use to indicate body fat content and classify underweight, healthy weight, overweight, and obesity. You only need your weight and height to calculate your BMI.
Use this formula: Weight (kg) divided by height squared (m2 or m x m).
Having a BMI under 18.5, you are underweight. A body mass index between 18.5 and 24.9 is classified as normal. Overweight is classified with a BMI between 25 and 29.9. Obesity is marked by a body mass index above 30.
If you weigh 90 kg with a height of 1,85 m, you have a BMI of 26,3. You are slightly overweight. But, if you gain weight and your scales show 103 kg, you are obese (BMI 30,1).
Calculation: 103 kg / (1,85 m x 1,85 m)
What are the limitations of BMI?
Working with BMI has some limitations because it is based on height and weight only. Therefore, it does not include sex, age, or body composition such as fat or muscle mass. Furthermore, the body mass index does not take into account that muscles weigh more than fat. So, athletes, bodybuilders, and pregnant women cannot use BMI due to falsified data. The problem is that the body mass index does not take physical activity and sports into account. As a result, people with different body compositions may have the same BMI.
To sum it up: The body mass index is a good indicator of your first orientation to target your desired weight.
What is the Waist-To-Height Ratio?
The waist-to-height-ratio is a more reliable tool for the prediction of developing chronic diseases such as heart disease, type 2 diabetes, and high blood pressure.
Therefore, you just need a measuring tape, stand straight, breathe deeply in, and exhale. Then, measure between your hip bones and the bottom of your ribcage. The simple message is: Keep your waist circumference to less than half your height! So, if you are 170 cm tall, your waist circumference should be max. 85 cm!
Many studies have shown that it is not too much body fat but especially too much visceral body fat, also called abdominal fat, which increases the risk of dying prematurely. Visceral or abdominal fat is the fat around our internal organs which is the most harmful. Waist circumference is predicting mortality from e.g. diabetes or cardiovascular diseases better than the body mass index.
Here are some tips on how to maintain weight loss after diet. And some facts about fats and oils in your nutrition.
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Here’s the scientific evidence this blog post is based on
Chang, S. H./Beason, T. S./Hunleth, J. M./Colditz, G. A. 2012: A systematic review of body fat distribution and mortality in older people, in: Maturitas, Vol. 72, 2012, No. 3, pp. 175-191.
Hajian-Tilaki, K./Heidari, B. 2015: Is waist circumference a better predictor of diabetes than body mass index or waist-to-height ratio in Iranian adults?, in: International Journal of Preventive Medicine, Vol. 6, 2015, No. 1, p. 5.
Leitzmann, M. F./Moore, S. C./Koster, A./Harris, T. B./Park, Y./Hollenbeck, A./Schatzkin, A. 2011: Waist Circumference as Compared with Body-Mass Index in Predicting Mortality from Specific Causes, in: PLoS ONE, Vol. 6, 2011, No. 4, pp. 1-8.
Zhu, Q./Shen, F./Zhou, Q./Deng, H./Gu, X. 2014: Waist-to-height ratio is an appropriate index for identifying cardiometabolic risk in Chinese individuals with normal body mass index and waist circumference, in: Journal of Diabetes, Vol. 6, 2014, No. 6, pp. 527-534.