What is BMI?
BMI is a calculation based on height and weight. The result is used as a general measure of body weight in relation to height.
BMI can be useful for assessing health risks at a population level, but it has limitations at an individual level. Two people can have the same BMI, for example, while their body composition differs significantly.
Someone with relatively high muscle mass can have a similar BMI to someone with a higher percentage of body fat, even though their underlying health profiles may be different.
What is meant by body composition?
Body composition describes the proportion of fat mass, muscle mass, bone mass and body water.
When assessing health, it is not only the amount of fat that matters, but also where that fat is stored. In particular, visceral fat (fat tissue surrounding the abdominal organs) is receiving increasing attention because of its relationship with metabolic health.
Changes in muscle mass can also be relevant. Muscle tissue plays an important role in energy expenditure, glucose regulation and physical functioning.
Why does weight not tell the whole story?
Body weight can change throughout life due to a range of factors, including age, lifestyle, hormonal changes and changes in muscle mass.
Particularly during hormonal transitions such as perimenopause and menopause, changes in fat distribution and body composition can occur without a significant change in total body weight.
As a result, someone may maintain the same weight while the ratio between muscle mass and fat mass changes.
This illustrates why health assessment is not based solely on weight or BMI, but is increasingly considered within the broader context of metabolic health.
Body composition and metabolic health
Fat tissue is not simply a storage site for energy; it also plays a role in various hormonal and metabolic processes.
An increase in visceral fat is associated with changes in insulin sensitivity, cholesterol levels and cardiovascular risk factors. Insulin resistance can also be associated with changes in body composition.
For this reason, there is growing attention to the relationship between fat distribution, muscle mass and long-term health.
When can assessing body composition be useful?
Assessing body composition can be relevant when you want more insight into metabolic health than body weight alone can provide.
This may be useful in relation to:
- changes in fat distribution
- hormonal changes during different stages of life
- metabolic risk factors
- changes in muscle mass
- cardiovascular risk factors
Body composition should always be interpreted in the context of age, stage of life, medical history and individual health factors.
It provides additional information about fat mass, muscle mass and fat distribution, offering a broader picture of health than weight or BMI alone.
