“Body composition is most often viewed in the context of the two compartment model : body mass is a combination of fat free mass and fat mass…
Low body fat content is associated with better performance in most endurance activities.
Researchers have found that the athletes with lower body fat percentage had higher maximum oxygen uptake…furthermore percent body fat is negatively correlated with total race time in male ironman athletes.
On the other hand muscle mass is considered a favorable factor in endurance performance.
Skeletal muscle is the largest tissue in the body and the main energy-consuming and work-producing tissue, providing the propulsive force to perform physical activities.
Fat has four key negative effects on running capacity:
Increase energy costs
Hampers running economy
Lessens ability to accelerate