There are differences between lean mass and fat mass, especially in diet.  Knowing them helps to better develop weight loss diets.

Although many nutritionists and dietitians have at their disposal a whole set of tools and useful elements to know a person’s weight (a good example of this is the BMI calculator), always knowing a person’s body weight can be misleading.

This is because the most basic tools that a nutritionist has sometimes may not clarify in what percentage a person’s fat is distributed, whose diet may depend on the volume or percentage of fat that the patient has.

For this reason, it is advisable to know the differences between lean mass and fat mass.

Main differences between lean mass and fat mass

What is lean mass?

The lean mass is made up of internal organs, muscles and bones. In this sense, in men, muscle mass tends to represent approximately 45% of their weight. While, in women, their muscle mass reaches only 35% of their weight.

Defining it more specifically, we can say that lean mass is the entire mass of our body that is not fat, and can be not only bone, but also muscles and other tissues (such as organs).  That is, it is the fat-free body mass.

It is, for example, something very important for the bodybuilder or for the person who practices fitness, since their objective is to try to lose weight while maintaining or increasing their own lean mass, being a useful indicator to discover that the muscle mass is it has remained the same – or has increased – while losing fat.

What is fat mass?

Unlike lean mass, fat mass is that formed above all by structural and storage fats.  In man, deposit fat reaches 12% and structural fat 3%. While, in women, their deposit fat rises to 14%, and structural fat reaches 12%.

But it is not the same to talk about fat percentage and body mass index. And it is that in the case of fat mass corresponds to adipose cells, while as we indicated above, lean mass corresponds, among other aspects, to muscles.

Different methods are used to measure the percentage of body fat:

  • The measure of the skin fold, measuring the thickness of a skin impingement in different parts of our body. It is useful to know the subcutaneous fat.
  • Bioelectric impedance, by which an electric current is passed through the body, so that its resistance is linked to the rate of fat.

In addition to these two tools, it is also possible to use an empirical formula derived directly from the Body Mass Index (BMI), providing the possibility of calculating the percentage of body fat (BMI). However, it is a formula only useful for people between 15 and 50 years of age.

Why is it useful to know the fat and lean mass of a person?

For a dietitian, it is extremely useful to know how much lean and fat mass the patient has, since the objective is to develop a suitable diet to lose fat mass, avoiding the least possible loss of lean mass.

For this, it is essential that the diet has an adequate content of foods rich in protein and carbohydrates. Of course, the latter must only provide the calories that the body needs each day, to prevent it from consuming muscle as an energy source.


Please enter your comment!
Please enter your name here