As an example eating a whole cake is generally considered unhealthy and a bad kind of stress for the body do to excessive calories and the glicemic level increase. Same thing when it comes to not sleeping enough.
Exercising and other activities on the other side are seen as fundamental to live a healthy life.
What exactly determines the difference? Is it just a matter of whether or not our body can “improve” following the stimuli? And why does our reactions varies so broadly?