The 10 most important questions about BMI for adults and BMI for children
What is BMI or body mass index?
The body mass index (BMI) can be used to assess whether you are underweight, normal or overweight. Here, the body weight is evaluated in relation to the body height. The weight (in kilograms) is divided by the square of the height (in metres). BMI is thus measured using the International System of Units (SI) in kiolgrams and metres. Converted into Anglo-American units, the formula for BMI is: 703 × weight in lbs / (height in inches)². When assessing the BMI, gender and age play an important role. For men, the normal weight is between 20 and 25 kg/m², as they have more muscle mass than women. For women, a BMI between 19 and 24 kg/m² is considered normal weight.
At what point is an adult considered morbidly obese?
If the body has too much fat and the BMI value is between 25 and 29.9, this is considered overweight (preadiposity). If the BMI is between 30 and 39.9, this is called morbid overweight (also called obesity or adiposity). A BMI of more than 40 is called extreme obesity.
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Why is overweight in adults harmful?
Too much body fat can cause a number of diseases because it puts a strain on the whole organism. The cardiovascular system is particularly affected. High blood pressure often occurs, and the risk of a heart attack increases with every kilo of excess weight. In addition, blood lipid levels often increase, which also increases the risk of heart diseases such as angina pectoris or chronic heart failure. Another widespread secondary disease is diabetes mellitus type 2. Gallstones, lipometabolic disorders and fatty liver degeneration can occur. On a psychological level, overweight people not infrequently suffer from low self-esteem and depression.
What can be done to prevent obesity?
A normal weight is maintained primarily through a healthy, moderate diet that is not too high in calories, combined with sufficient exercise. The body also needs fewer calories with increasing age, which is why older people should eat less.
How is overweight treated?
Treatment of obesity is multi-pronged. First and foremost, one must change their diet to a healthy, low-calorie and balanced one with the goal of losing weight and permanently changing their lifestyle. For example, it is important to consume low-fat foods, lots of vegetables and fruit, and whole grain products. Meat consumption, on the other hand, should be reduced. It is also important to drink plenty of fluids, especially water. In addition to a healthy diet, regular and sufficient exercise is very helpful. This can be achieved by participating in moderate endurance sports such as swimming, cycling or Nordic walking. Therapy, which includes awareness of the psychological causes of weight gain and unhealthy eating habits, is also a viable method of treating obesity. In the case of extreme obesity, surgical interventions such as gastric banding, stomach tube formation or gastric bypass are used.
How is the BMI for children calculated?
The BMI is interpreted differently for children than for adults. While adults are divided into weight classes based on BMI values, the assessment of BMI for children is based on age- and gender-dependent reference curves. Here, one deliberately falls back on older reference curves or percentile values, in which slimmer children served as the basis for the norm. According to this, children are considered overweight if their BMI is above the 90th age- and gender-specific percentile. This means that 90% of the children in this age group and of the same sex have a BMI value below the 90th percentile. The 10 percent above this is considered overweight, with a BMI value of 97 percent or more being considered obese.
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How does childhood overweight develop?
Children who spend a great deal of time in front of computers and game consoles are especially prone to becoming overweight as a result of their sedentary lifestyles. This can be compounded by a genetic predisposition, especially if other family members also suffer from obesity. Unhealthy diets based on high-fat, high-calorie foods and fast food contribute significantly to the rising rate of overweight children.
When are children particularly at risk of obesity?
During certain growth phases, children are at a higher risk of becoming overweight. So, by the time a child starts school, he or she must adjust to long periods of sitting with hardly any movement. In addition, he or she must also address host of new challenges. These are often compensated for with soul comforts such as crisps, fatty foods or chocolate. During puberty, when profound physical and emotional changes take place, children also tend to reach for sweets, high-calorie foods and fast food more often.
How can overweight in children be prevented?
Certainly, a healthy, balanced diet and regular exercise are fundamental to preventing a child from becoming overweight. However, parents also have an important role to play, because only if they themselves practice this lifestyle will their children follow suit. Children should be encouraged to be active outdoors instead of sitting for hours in front of the computer or television. Eating together with the family on a regular basis is an important ritual that can contribute to a healthy lifestyle and also help to curb constant eating on the side.
How is childhood overweight treated?
If an individual is only slightly overweight, there is often a chance that it will grow out of this weight with the help of calorie reduction and exercise. The paediatrician is best placed to assess this possibility. If a child is morbidly obese, the whole family must be involved in therapy. At the beginning of treatment, the menu for all family members is changed to a low-calorie and healthy diet. The family should also actively support the overweight child in sporting and leisure activities, for example by embarking on bike tours and hikes together or playing football together. In this way, the child will find exercising enjoyable again.
As source for the information in the 'Body Mass Index' category, we have used in particular:
- WHO Body mass index - BMI (WHO)
- Diet and Health: Implications for Reducing Chronic Disease Risk (National Research Council (US) Committee on Diet and Health)
Last update on February 20, 2023
The pages of the 'Body Mass Index' category were last editorially reviewed by Stefan Banse on February 20, 2023. They all correspond to the current status.
Previous changes on October 19, 2022
- Editorial revision of all texts in this category