As compared to sedentary counterparts, trained athletes can perform at a higher intensity of exercise and for a longer period of time because

answer; genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes;

starvation is bad because your body needs nutrition and to deprive it of nutrition can cause problems with both health and fitness.

explanation:

it can make weight loss slow down over time, but it won't cause someone to gain weight depsite restricting calories. starvation causes weakness in the senses like thirst.