Calculate, understand and evaluate BMI (Body Mass Index).

Summary of this blog

The blog comprehensively explores the topic of BMI (Body Mass Index), covering its definition and calculation, along with critical considerations and supplements to its significance. Here is a summary:

The Body Mass Index (BMI) is used to estimate the body's fat percentage based on the ratio of body weight to height. Adolphe Quetelet developed the formula in 1832. BMI is categorized into different classes representing medical weight statuses. However, BMI does not take into account muscle mass, neglecting important aspects. Health is influenced by various factors, and overweight becomes relevant only in connection with other conditions such as diabetes.

BMI categories range from underweight to Obesity Grade 3, with higher values associated with an increased risk of health problems. However, the overall condition of an individual is crucial in this context. The distribution of body fat, especially in the abdominal area, plays a role and can be measured in addition to BMI.

The text highlights the limitations of BMI, including the neglect of muscle mass, the lack of consideration of individual differences in people of different origins, and the absence of a precise assessment of fat distribution. Particularly in children, BMI must be evaluated differently as they are in a growth phase.

A dedicated section covers the calculation of BMI using a mathematical formula and a calculator. The blog concludes by stating that many consider BMI useless as it does not adequately convey information about fat mass and its distribution. The location where fat accumulates in the body influences health and life expectancy, irrespective of BMI. The text emphasizes that regular physical activity and a high muscle mass from midlife onward can improve life expectancy.

End of summary

What is BMI (Body Mass Index)?

Through the application of the Body Mass Index, an estimation of the fat percentage in the human body can be made. This value is calculated based on the relationship between height and weight and is also referred to as the Body Mass Index or body mass number. The formula for calculating the BMI was developed in 1832 by Adolphe Quetelet to provide individuals with a precise assessment of the ratio of body weight to height. It should be noted that the determined BMI can only serve as a rough guide, as both muscle mass and adipose tissue are disregarded.

Following the calculation of the Body Mass Index, the weight is categorized into the following classifications:

The sole reliance on the Body Mass Index provides only limited information. Numerous other factors influence health. Although a Body Mass Index in the range of 25 to 30 is medically considered overweight, studies suggest that this does not significantly impact life expectancy or various medical conditions. The relevance of overweight becomes particularly apparent when other illnesses, such as diabetes, coexist.

A Body Mass Index over 30, classified medically as obesity, can indeed have adverse effects on health and life expectancy. Severe obesity increases the risk of associated diseases. Nevertheless, the overall condition of an individual remains crucial. Individuals with obesity can still be physically fit and have a healthy cardiovascular system. However, weight loss can improve overall health.

Not only does body weight pose a risk for cardiovascular diseases, but factors such as age, gender, blood pressure, cholesterol levels, genetic predisposition, diabetes, and smoking also play a role. Therefore, obesity should always be considered in conjunction with these risk factors.

The distribution of body fat also plays a role. Research shows that fat deposited in the abdominal region causes more significant health issues as it strongly influences metabolism. Hence, it is advisable to consider not only the Body Mass Index but also the waist circumference. A waist circumference over 102 cm in men and over 88 cm in women is considered medically concerning. However, individual body structure is not taken into account. The normal body fat percentage ranges from 8 to 25 percent in men and from 20 to 35 percent in women. Commercial scales exist that allow an estimation of body fat percentage.

Body Mass Index calculators do not account for muscle mass. In muscular individuals, the fat percentage is overestimated, while in older individuals, it is underestimated as muscles decrease with age. Additionally, BMI categories from Western countries are less suitable for individuals of different origins. In people from Southeast Asia, the body fat percentage is underestimated, and in black individuals, it tends to be overestimated.

BMI difference between adults and children

By utilizing a BMI calculator for children, it can be determined whether a child's body weight is developing normally. Similar to adults, the Body Mass Index serves as an indicator for youngsters, signaling whether they are underweight, within the normal range, or overweight.

For adults, the BMI value serves as a global standard for self-assessment of weight. According to the guidelines of the World Health Organization (WHO), the optimal weight range for adults is between 18.5 and 24.9.

Calculating the BMI value for children requires an adjusted calculation. Children are still in the growth phase, and the development of body fat mass can vary significantly during these growth stages. Some children experience sudden growth spurts and appear very slender, while others retain baby fat for a while, gradually decreasing over time. When calculating the Body Mass Index for children, the gender-specific developmental differences between girls and boys need to be more carefully considered.

If a child's Body Mass Index falls at the upper or lower limit, consulting a pediatrician is advisable.

BMI calculator

Enter your height in centimeters and your weight in kilograms in the following BMI calculator, and confirm by clicking the "Calculate BMI" button.

[bmi theme=”material” metric=”cm/kg” imperial=”in/lb” submit=”Calculate BMI”]

Even individuals with a weight classified as normal often perceive themselves as too heavy, despite their weight falling within the normal range according to medical standards. A BMI calculator provides indications of where your weight falls within a range. The BMI table is based on categories defined by the World Health Organization (WHO). The range for weight classified as normal is quite extensive. Achieving a healthy physique does not necessarily require being thin.

The Body Mass Index provides only a rough estimate. Individuals with a high proportion of muscle mass may have a high BMI without being considered overweight. The BMI value does not provide information about the distribution of body fat. Particularly, abdominal fat poses health risks. Age and gender are also taken into account in the evaluation using a BMI table. Many experts now tend to believe that the ratio of waist circumference in centimeters to height in centimeters is more meaningful. A value below 0.5 is considered desirable, and for older individuals, even below 0.6. The waist circumference itself also provides a rough guideline. For men, it should not exceed 102 centimeters, and for women, it should not exceed 88 centimeters.

Children have their own standards. There are special BMI charts for children, but they serve only as rough guidelines since children are still in the growth phase. If you have concerns about your child's weight, consulting with a pediatrician is advisable. Never put your child on a diet without professional advice.

The BMI categorization by the World Health Organization (WHO) is as follows:

You have the option to independently calculate your Body Mass Index using a calculator. However, it's quicker to utilize the numerous BMI calculators available online for children, women, or men. Whether it's a BMI calculator for women or men, they all employ the same formula for calculating the Body Mass Index and should therefore yield identical results.

BMI table

Once you have determined your BMI value, take a look at a BMI table. These classifications categorize the various results into groups such as severe underweight, excessive and mild underweight, normal weight, as well as pre-adiposity and obesity Grade 1 to Grade 3.

Not only does gender play a role, but age does as well. Generally, men are assumed to have higher muscle mass than women, leading to different upper limits for men and women. There are also variations in calculating the BMI value for children, where age is also a factor in the classification.

If you find through the Body Mass Index calculator that you are overweight, it is recommended to maintain a healthy and balanced diet and engage in regular physical activity, ideally at least two to three times a week.

Calculate BMI with mathematical formula

In the 19th century, Adolphe Quetelet developed the Body Mass Index to quantify body mass, as mentioned earlier. This measurement is independent of gender and age, which is why it utilizes the same formula for men, women, and children. The calculation of the Body Mass Index is done according to the following formula:

Body weight in kilograms divided by the square of height in meters
BMI = x / (y × y)

x = Body weight in kg
y = Height in m

An example for an individual with a height of 170 cm and a weight of 80 kg:

Assuming you are 1.70 meters tall and weigh 80 kilograms, the calculation is as follows:
1.70 × 1.70 = 2.89
Now, divide your weight by this value:
80 : 2.89 = 27.7
27.7 – rounded up to 28 – is your Body Mass Index.
BMI = 80 / (1.70 × 1.70) = 27.68

The interpretation of the respective value can be looked up in a BMI table.

Calculating the BMI with a calculator:

Total time: 1 minute

Enter the initial number into the calculator.
Record the body weight in kilograms (70).

Press the first mathematical symbol.
Divide it by.

Enter the next number into the calculator.
Add the body height in meters (1.75).

Press the second mathematical symbol.
Divide it by.

Enter the last number into the calculator.
Input the body height in meters (1.75).

Press the concluding symbol.
Now, tap on the "Equals" (=) symbol.
The result is 22.86.

Why many consider the body mass index to be meaningless

The standard for assessing weight, which was long attributed to the Body Mass Index, has lost significance. Nowadays, researchers place more emphasis on understanding the body's fat mass and its distribution. Relying solely on the Body Mass Index is no longer advisable. The type of fat distribution provides a more meaningful indication of potential health risks.

A distinction is made between an apple- or pear-shaped body. In the case of the apple variant, fat is primarily deposited in the abdominal area, posing an increased risk of heart attack and diabetes. Therefore, measuring waist circumference is advisable. The measurement is taken in the middle between the last rib and the upper edge of the pelvic bone. The measuring tape is placed horizontally around the waist, and the waist circumference is read after exhaling. In women, the waist circumference should be below 80, and in men below 94 centimeters. An increase in health risks begins for women above 88 and for men above 102 centimeters in circumference.

However, this theory is also quite rigid. Studies have shown that overweight individuals do not necessarily die earlier than those with normal weight. Nevertheless, caution is warranted, as a higher Body Mass Index can shorten life expectancy in some cases and improve it in others. Sometimes, no clear correlation is discernible.

The Body Mass Index has significant weaknesses that impair its meaningfulness. The calculation considers only the total weight, not the composition of muscles, which are denser and heavier, or lighter fatty tissue. Movement habits are also neglected, although they have a significant impact on health. Likewise, body fat distribution and age are not taken into account. With increasing age, the body undergoes significant changes: fat percentage increases, while body water, bone, and muscle mass decrease.

Information:

Learn how to build muscles even in old age: Muscle Building in Old Age: How to Stay Fit and Healthy

The region where fat accumulates affects health and lifespan, even if the Body Mass Index shows no signs of overweight. Individuals with an apple-shaped figure store fat in the midsection, while those with a pear-shaped figure tend to accumulate it in the thighs and buttocks. The apple type is at a disadvantage as abdominal fat is hormonally active and can increase the risk of various diseases such as heart attack or diabetes.

Therefore, the Body Mass Index proves to be unsuitable for determining an optimal weight for the entire life. Only in individuals with extremely high or low BMI values of over 35 or under 18.5, studies show that the risk of premature death is elevated. A thorough examination by your family doctor can help determine whether weight loss is advisable or not. Your doctor will take into account additional factors and provide you with a personalized recommendation. However, for all weight classes, it is established that regular physical activity contributes to increasing life expectancy. Individuals with a high muscle mass from midlife onwards enhance their prospects of living long, healthy lives without restrictions.