BMI (Body Mass Index) measures the ratio between weight and height. It is one of several ways to determine if you weigh too much or too little. A normal BMI, according to WHO, is 18.5-24.9. Values above or below normal can sometimes lead to health risks – a high BMI combined with a large waist size, for example, increases the risk of type 2 diabetes, high blood pressure and cardiovascular disease.
BMI table – WHO international guidelines:
- underweight – BMI below 18.5
- normal weight – BMI 18.5-24.9
- overweight – BMI 25-29.9
- obesity – BMI over 30
It is important to remember that BMI is a rough measure that does not give a complete picture of how your weight affects your health.
Therefore, it is good to also check your waist size – measure just above the navel. A large waist size also poses health risks, even if you have a normal BMI. For men, the risk of illness increases if the waist size exceeds 94 centimeters, for women the corresponding figure is 80 centimeters.
How to calculate your BMI
To find out your BMI, divide your body weight (kilograms) by your length (meters) in the square.
BMI is an indication, not an absolute truth
BMI does not take into account whether you are male or female, how old you are, how you are built or how good your fitness is. BMI also does not show how fat is distributed or how much of your weight is made up of fat and muscle respectively.
Good to know:
- Abdominal fat is an important warning signal – a lot of fat around the stomach is worse for health than, for example, fat around the hips. A higher BMI, but with the weight evenly distributed, entails fewer health risks than a normal BMI with too much abdominal fat.
- Exercise reduces the risk of disease – the higher the BMI of a person with good physical condition is not as alarming as physical inactivity in normal-weight people.
Limit values for BMI vary with age
For people over 50, the BMI limits for obesity may be higher than for younger adults. For people over 70, a BMI of 25-30 can be most healthy, while a BMI of under 22 can be a sign of malnutrition. If you exercise a lot and weigh more because you have built up your muscles, the BMI scale will also be misleading.
BMI in children has other limit values - underweight and obesity have lower limits than in adults and also vary during adolescence depending on age and length growth.
Health risks: high BMI
An unhealthy overweight person with too much body fat increases the risk of suffering from various diseases, such as type 2 diabetes, high blood pressure, elevated blood fat and cardiovascular disease. The risk of osteoarthritis and some cancers also increases. It can also be more difficult to get pregnant – obesity can cause infertility problems in both women and men. The higher the BMI, the greater the health risks. A BMI over 40 means a more than ten times greater risk of dying prematurely.
Not all people with a higher BMI have the same increased risk of illness. The waist size and genetic factors should also be weighed, as well as lifestyle and general health.
Health risks: low BMI
An unhealthy underweight person, with too little body fat and muscle mass, can have serious consequences. A lower energy intake in relation to needs often leads to abdominal pain and sleep problems, lower performance and makes you tired and cold.
Underweight can sometimes also lead to wounds, infections and anemia. Blood pressure and resting heart rate can be unhealthily low, causing a blood pressure drop and dizziness with syncope risk, decreased energy, depression, as well as confusion, drowsiness and slow breathing. There is also a risk of fall injuries as a result of decreased muscle mass, especially among the elderly who suffer from malnutrition. In severe cases of malnutrition, for example in connection with eating disorders, the body’s temperature may fall below 35 degrees (so-called hypothermia).
How can you influence your BMI
In order to maintain normal weight and have a healthy waist measurement and BMI, you usually need to prioritize healthy diet and physical activity. A normal energy intake for an adult male is 2500–3000 kcal (kilocalories) per day, for an adult female 2000–2500 kcal per day. A good yardstick for exercise is to be physically active for at least 30 minutes a day. Sleep is also important. In addition, it is wise to try to reduce stress, drink alcohol moderately and avoid smoking.
This is general advice. There are many other factors that affect your weight and your BMI, such as different disease states.
When to consult a doctor
If you have a BMI under 18, you should get medical advice to help increase your nutritional intake. If you have an unhealthily high BMI that limits your everyday life, or that gives symptoms like high blood pressure, you should also contact your healthcare provider.
How APPOTEK can help
You can contact us at APPOTEK for help with aberrant BMI. A nurse or a physician will make an individual assessment based on your symptoms, after which you may be prescribed treatment or referred for further examination.
If your child has a problem, he or she should see a doctor.