Weight is often evaluated by the Body Mass Index (BMI). However, its validity is limited. We show you if an ideal weight can be defined – and what the consequences of being over- or underweight can be.
The World Health Organization (WHO) defines weight categories according to the Body Mass Index (BMI).
To calculate BMI, divide your body weight (in kg) by the square of your height (in m). An example: the BMI of a person with a height of 1.75 m and a weight of 70 kg is 22.86 kg/m2.
The following values apply for adults over 20 years of age:
From a medical perspective, just looking at a person’s BMI, weight or waist circumference does not allow you to form an opinion about their health. In most cases, weight is not the cause, but rather a symptom of an unhealthy lifestyle or a physical problem. You can find further information on this topic below.
The BMI only compares weight in relation to height. A more advanced form of the BMI, the Smart Body Mass Index, also includes age and sex. Neither method takes account of your build or the ratio of fat to muscle mass. Therefore, athletes often have a BMI in the overweight range, without having increased body fat.
The terms normal and ideal weight are often used interchangeably. However, they do not mean the same thing. Normal weight is calculated using the BMI. Depending on your height, there is a weight range that is deemed “normal”. Conversely, ideal weight is personal. It depends on a person’s goals and what aesthetic appearance they are aiming for.
However, weight is not only associated with health and physical well-being in our society. It strongly influences our lives – from our career to our choice of partner. As a result of this social pressure, even healthy people with a normal weight often wish for a slimmer figure. On the other hand, there are also people who are comfortable with being overweight, and thus consider this weight to be the ideal weight.
David Fäh, doctor and nutritionist, says: “There is no simple answer to the question of what an ideal body looks like. I realise this time and again when I see athletes: while shot-putters are mostly severely overweight, marathon runners are often on the verge of being underweight. However, both are probably healthy. Radical diets make little sense to achieve your ideal weight. Often you lose sugar reserves, water or muscle mass and not the desired fat – those lost kilos are quickly regained. It is much more sensible and easier to maintain your own body weight. If you take care not to gain weight as you get older, you will come closer to your desired weight in the long run.”
Weight fluctuations of up to three kilos within a short period of time are normally no cause for concern. Possible reasons for this are changes in the body's water balance or carbohydrate stores. For example during intensive exercise, the body can lose between 1–2 kg. But if our digestive tract is full, this can also affect the number on the scales.
However, you should seek medical advice if you unexpectedly lose or gain weight without explanation within a few months. Because such weight fluctuations can indicate diseases:
Our health advisors can provide you with helpful information on this subject. They will also support you if you want to change your diet or integrate more exercise into your everyday life.
The number on the scale does not only depend on what we eat and how often we exercise. There are many other factors:
People who are within the range of normal weight according to the BMI have a lower risk of diseases related to body weight. On the other hand, being severely over- or underweight can have serious consequences on health.
Physical consequences of being overweight:
Physical consequences of being underweight:
David Fäh lectures and conducts research at the Bern University of Applied Sciences, School of Health Professions, Specialist Area Nutrition and Dietetics. He provided the editorial team with advice and input for this article.