What type of body structure can gain weight quickly and has proportionally growing muscles?

The type of body structure characterized by the ability to gain weight quickly and exhibit proportionally growing muscles is the mesomorph. Mesomorphs typically have a naturally athletic build with higher levels of muscle mass and lower levels of body fat, which allows them to gain muscle quickly when strength training and to add weight more easily than other body types. Their muscular composition makes it easier for them to achieve a well-defined physique, as their bodies respond favorably to exercise, particularly resistance training.

Individuals with this body type often find that they can increase their muscle mass with relatively less effort compared to other body types. Their natural distribution of muscle tends to be well-proportioned, contributing to an aesthetic appearance. This explains why they are often seen as having a more favorable genetic predisposition for bodybuilding and athletic pursuits.

In contrast, endomorphs may gain weight more easily but typically have a higher body fat percentage, while ectomorphs tend to be skinny and struggle to gain weight, lacking the significant muscle mass seen in mesomorphs. The description of an "obese body type" does not accurately represent a specific somatotype but rather indicates a condition that can arise in any body type depending on lifestyle and diet.