Overall Change in Body Composition – How is it calculated?

The Challenge Wizard report system provides challenge organisers with an easy way of tracking the overall changes in body composition over time. Rather than relying solely on weight loss, or change in percantage body fat, the goal of the calculation is to identify individuals who have improved their overall body composition by increasing their lean body mass combined with their loss of fat mass. The overall percetage change in body composition was created to be a fairer system of comparing leaner individuals to obese individaulas competing in the same challenge.  Through assessment of the change in lean body mass in comparison to starting levels, combined with change in body fat mass in comparison to staring levels relative to staring weight allows all participants to be judged in a consistent fashion. 

Take a look at the following scenarios with our two example challenge participants, Bill and Ben.

Bill weighs a total of 200lbs with 25lbs of Fat Mass which puts his body fat percentage at 12.5%, while Ben weighs a total of 250lbs with 65lbs of Fat Mass and sits at 26% body fat.

overall change body composition

Ben has a far greater initial Fat Mass than Bill, which theoretically should make it much easier for Ben to lose 10 pounds of body weight than Bill, giving Ben a clear advantage if a challenge was judged on weight loss alone.

Challenge Wizard adjusts for any initial advantages Ben may have in the weight loss stakes and seeks to find a winner based on the overall percentage change in body composition (lean body mass and fat mass).

Change in Fat Mass

If Bill and Ben were to each lose 10 pounds of body fat, they would effectively be equal in terms of weight loss. However, by taking into account the percentage of change relative to their starting weights, its can be seen that Bill's fat loss is being reflected as more significant.  This is due to a generalised increased difficulty for leaner individuals to lose body fat than their more obese counterparts.

In our example, Bill would have a 5% positive change while Ben sees a 4% positive change.

Fat Mass challenge equation

Change in Lean Body Mass

Let's see what would happen if Bill were to also gain muscle 5lbs of Lean Body Mass and Ben were to lose 5lbs. A gain in Lean Body Mass would cause an increase in overall weight but would be considered to be positive change.  In contrast, a loss of lean body mass would increase overall weight loss despite being considered a negative change.

Assuming that both individuals have a start Lean Body Mass of 180 lbs. By comparing the change in Lean Body Mass to the beginning Lean Body Mass we can see that Bill's 5lbs gain in lean body mass results in a positive change of 2.77% whereas Bens 5lbs loss of lean body mass results in a negative change of 2.77%.

lean body mass equations

Overall body composition change

Using the Challenge Wizard overall change in body composition formula and applying Bill and Bens change in Fat Mass and Lean Body Mass we end up with the following-

Bill has an overall change of 7.77% while Ben's overall change is 1.23% making Bill the clear winner.

overall body composition equations

As Bill gained 5lbs of Lean Body Mass and lost 10lbs of fat mass his overall net weight loss would only 5lbs. Compare this to Ben who also lost 10lbs of fat mass but lost 5lbs of Lean Body Mass.  Ben's overall net weight loss would be 15lbs. (5lbs vs 15lbs).  If the emphasis of a challenge is placed on weight loss only, Ben would be the clear winner despite not having the best change in body composition.

Why do we compare change in Fat Mass to the Start Weight instead of comparing it to the start Fat Mass?

Just as measuring a challenge using weight loss alone places a heavy bias towards heavier individuals, using starting fat mass in the equation swings the bias heavily in the opposite direction.

If we substitute starting Fat Mass for starting weight in the Fast Mass equation we would end up with Bill having a 40% positive change(10/25 x 100) gain compared to Ben's  15% positive change (10/65 x 100).  This would make Bill's Fat Mass loss more than 2 and a half times better than Bill's.  Using start weight in the Fat Mass formula mostly flattens any bias enabling a fairer comparison of individuals all sizes.

The Challenge Wizard reports are designed to make it easier and fairer to determine the winners of challenges by combining positive fat mass loss with positive lean body mass gains which are the markers of a healthier body composition.  We hope that this helps explain the calculations used in our reports.