You are most likely aware of your weight, of what the digits on the bathroom scales read, but how useful is this really? You may even be familiar with your body mass index (BMI) which is used to classify people into underweight, normal, overweight or obese, yet even this is not a true reflection of you. It is merely looking at your weight corrected for your height. A rugby player may well be classified as obese if we go by BMI, though that is certainly not a true depiction of his or her morphology.
To use the phrase “it is what’s inside that counts” leads us nicely onto the concept of body composition, which importantly looks at what your bodyweight is made up of. In other words, its composition.
The term body composition encompasses a range of different representations of the body’s make-up, from the simple to the complex. In its simplest form, body composition describes the body as composed of two components, fat mass (FM) and fat-free mass (FFM), commonly called “lean tissue”. Fat mass regards all the fat in the body, virtually all of which is housed within adipose tissue. The fat-free mass represents everything else, a collection of organs, bone, muscle and water.
This simplified view of the body is the most widely used, often depicting fat mass as a percentage of body weight (% body fat), and FFM as an absolute weight or as a percentage of body weight. In this way, an individual can be much more accurately characterised. For example, the rugby player characterised as “obese” using BMI will clearly have a higher FFM and normal or low percentage of body fat.
However, body composition can be much more informative than simply ‘fat’ or ‘lean’. Developments in techniques coupled with our understanding of body tissue metabolism have added weight (excuse the pun) to the importance of determining body composition. Body fatness – and how fat or lean you look – is not simply down to how much fat mass you have, but where that fat is located, particularly the amount in places it shouldn’t be. Hence fat distribution is a powerful indicator of health and wellbeing.
Similarly, quantifying components of fat-free mass (“lean tissue”), for example muscle, bone and body water (and even organs) are important. These refinements become increasingly relevant not just as a way of screening for health, but also in identifying what aspects to change to meet your goals.
Want to know more? Dr Adam Collins’ five-part short course is available for free via the Form website, covering key body composition factors including how to gain muscle, how to strip fat, and how to effectively measure your progress.
Dr Adam Collins PhD is Form’s head of nutrition and director of the MSc Nutrition course at the University of Surrey.