The BMI calculator is a simple tool for quickly estimating your body weight in relation to your height. It gives you an initial indication of whether your weight is within a healthy range or whether there may be a need for action. However, please note that the BMI is only a rough guide and does not take into account individual factors such as muscle mass, age and gender
Here are some of the most important questions and answers about the BMI (body mass index):
What is the BMI?
The BMI is a measure of body weight in relation to height. It is calculated by dividing body weight in kilograms by the square of height in meters[1][3].
How do you calculate the BMI?
The formula is: BMI = body weight (kg) / (height (m))²[1][3].
What do the different BMI values mean?
The following generally applies to adults:
- Under 18.5: underweight
- 18.5 – 24.9: normal weight
- 25.0 – 29.9: overweight
- 30 and higher: obesity (very overweight)[1][2]
Is the BMI equally meaningful for all people?
No, the BMI does not take into account individual factors such as age, gender, build or muscle mass. For very muscular people, children, adolescents and older people, it can lead to incorrect assessments[1][3].
How many people in Germany are affected by obesity?
Around 23% of men and 24% of women in Germany are considered severely overweight (obese), which corresponds to around 16 million people[4].
Are there alternatives to the BMI?
Yes, other methods of assessing body weight include measuring waist circumference, waist-to-hip ratio or body fat measurement[1][3].
Why is abdominal fat particularly dangerous?
Abdominal fat (visceral fat) is metabolically active and produces hormones and pro-inflammatory substances. It increases the risk of heart disease, type 2 diabetes and premature death[4].
How can you improve your BMI?
A healthy BMI can be achieved and maintained through a balanced diet, regular physical activity (e.g. running), sufficient sleep and stress management[5].
How often should I run to improve my BMI?
For beginners, we recommend running 2-3 times a week for 20-30 minutes. As your fitness improves, you can increase the frequency and duration. Regularity and a slow increase are important to avoid injuries.
Can I start running even if I have a high BMI?
Yes, but be careful. Start slowly, perhaps with a combination of walking and jogging. Consult your doctor beforehand if you have a BMI over 30. Good running shoes are particularly important to protect your joints.
How long does it take for my BMI to improve through running?
This depends on many factors, such as initial weight, diet and training intensity. In general, with regular training and a balanced diet, you will notice the first changes after 4-6 weeks.
Is running better for BMI improvement than other sports?
Running is very effective, but not necessarily “better”. It burns a lot of calories and is easily accessible. However, other endurance sports such as swimming or cycling can be easier on the joints, especially if your starting weight is high.
Why running is good for your BMI
Running is particularly effective for improving your BMI for several reasons:
- High calorie burn: Running burns more calories per unit of time compared to many other sports. A 30-minute run can burn between 200 and 500 calories, depending on the intensity and body weight1.
- Afterburn effect: After running, the metabolism remains elevated for several hours, which leads to additional calorie consumption.
- Muscle building: Regular running not only strengthens the leg muscles, but also the torso. More muscle mass increases the basal metabolic rate, which contributes to an improvement in BMI in the long term.
- Improving insulin sensitivity: Running can improve insulin sensitivity, which promotes fat burning and reduces the risk of type 2 diabetes.
- Stress reduction: Regular running reduces stress and can reduce emotional eating, which indirectly contributes to weight control.
- Accessibility: Running requires little equipment and can be practiced almost anywhere, making it easier to exercise regularly.
- Long-term weight control: Studies show that runners are better able to maintain their weight in the long term than people who do other sports.
Note, however, that an improvement in BMI is most effectively achieved through a combination of regular running training and a balanced, calorie-reduced diet. Running alone does not guarantee a BMI improvement if the diet is not adjusted.
How accurate is the BMI for children and adolescents?
The standard BMI is not meaningful for children and adolescents. Instead, age- and gender-specific BMI percentiles are used, which take growth and development into account.
Are there differences in BMI between men and women?
The BMI calculator itself does not differentiate between genders. However, women naturally have a higher body fat percentage than men, which should be taken into account in the interpretation.
How does muscle mass affect BMI?
Muscle is heavier than fat. Therefore, very muscular people, such as bodybuilders or certain athletes, can have a high BMI even though they are not overweight. This is a known limitation of the BMI.
What BMI is considered underweight and what risks does it entail?
A BMI below 18.5 is considered underweight. Risks can include a weakened immune system, osteoporosis, hormonal disorders, infertility and, in severe cases, organ damage.
How does age affect BMI?
Body composition changes with increasing age. Older people often have more fat and less muscle mass. Therefore, a slightly higher BMI can be considered normal for seniors.
What role does BMI play in the diagnosis of eating disorders?
BMI can be an indicator for certain eating disorders, but it is not the only decisive factor. In anorexia nervosa, a very low BMI is often a diagnostic criterion, while in binge eating disorders the BMI is often elevated.
How meaningful is the BMI for pregnant women?
The BMI is less meaningful during pregnancy. Instead, weight gain during pregnancy is observed, which should vary depending on the initial BMI.
Are there cultural differences in BMI assessment?
Yes, some Asian countries have lower BMI limits for obesity, as health risks can already occur at lower BMI values there.
How does water retention affect BMI?
Water retention can increase weight and therefore BMI in the short term without changing the body fat percentage. This can occur, for example, during the menstrual cycle or with certain medical conditions.
Can you have a healthy BMI and still be metabolically unhealthy?
Yes, this phenomenon is referred to as “metabolically unhealthy normal weight”. Despite a normal BMI, risk factors such as elevated blood lipid levels or high blood pressure may be present.
How does height affect the accuracy of the BMI?
The BMI can be less accurate for very tall or very short people. The weight of tall people tends to be overestimated, that of short people underestimated.
Sources:
[1] https://www.verbraucherzentrale.de/wissen/lebensmittel/schlankheitsmittel-und-diaeten/bodymassindex-was-kann-er-und-was-nicht-10441[2] https://adipositas-gesellschaft.de/aga/bmi4kids/
[3] https://www.umm.de/chirurgische-klinik/leistungsspektrum/adipositaschirurgie/body-mass-index/
[4] https://adipositas-gesellschaft.de/ueber-adipositas/fragen-und-antworten/
[5] https://www.stiftung-gesundheitswissen.de/gesundes-leben/ernaehrung-lebensweise/kennen-sie-ihren-bmi
[6] https://www.bmi.bund.de/SharedDocs/faqs/DE/themen/heimat/reform-staatsangehoerigkeitsrecht/reform-staatsangehoerigkeitsrecht-liste.html
[7] https://www.bmi.bund.de/DE/themen/heimat-integration/buergerschaftliches-engagement/haeufige-fragen-und-antworten/haeufige-fragen-und-antworten-node.html
[8] https://www.bmj.de/DE/themen/gesellschaft_familie/queeres_leben
