Tanita algorithms for calculating body composition have been refined using large population studies and comparisons with measurements of fat mass, lean mass and body water using a range of gold standard scientific methods. When comparing results, we have found that athletes have a significantly different body composition to the average population and therefore require a specific algorithm.

Athlete mode would therefore give a more accurate result for athletes (or individuals training to a professional standard), but a less accurate result when used for other individuals.  

Please check article below for when you should use Athlete Mode to get accurate results:

When to use Athlete Mode?