Are role-playing games healthy?

[Play] energizes us and enlivens us. It eases our burdens. It renews our natural sense of optimism and opens us to new possibilities... play is a catalyst. The beneficial effects of getting just a little true play time can spread through our lives, actually making us more productive and happier in everything we do.

— Stuart Brown, M.D., Play: How it Shapes the Brain, Opens the Imagination, and Invigorates the Soul

On fantasy:

Fears that gaming is unhealthy often center around the idea that games can blur the line between our shared, everyday reality and fantastical elements that may be present in games, or other things that may occur within a game. In fact, RPG players are no more likely to experience this confusion than actors or improv artists. RPGs are exactly improvisation, except that the rules for moving the story forward are different. If a potential player isn't at risk of mistakenly thinking their favorite TV show, book, or movie is nonfiction, they are very unlikely to come away from an RPG game thinking they can do fantastical feats, summon demons, or become a vampire. RPGs exercise the pretend-play skills of their participants; they do not try to convince players to believe in an alternate reality. 

Although care should be taken in considering whether RPGs are a safe form of play for someone who experiences delusions, the vast majority will have no confusion in distinguishing what happens in a game from what is true in life.

On physical fitness:

While tabletop RPGs (TRPGs) and role-playing video games are by nature sedentary activities, playing RPGs does not mean saying goodbye to the idea of physical activity and mouldering in a basement with glistening heaps of junk food. Players can and should take movement breaks, and GMs and parents can help them remember to do so on a regular basis. 

Live Action Role Play (LARP) and role play with live action elements are also possible where space permits. For example, if a character has decided to sneak across a bridge, a GM could require the player to act it out to the best of their ability, potentially while wearing bells, just as the player would be expected to voice an attempt to persuade someone else's character. In a LARP, all actions are performed, in a whole-body improvisation. 

RPGs can consist only of hours of sitting, but if you want them to involve movement and only (or mostly) healthy snacks, that power is yours.

On social skills:

RPGs are one of the few forms of currently popular games which are collaborative, not competitive. Because players must work together to achieve narrative goals, they must learn teamwork skills, as they would in sports. Players will learn how to fill a role on a team, and to judge when to be larger than that role and when to stand back and let others have their moments. Players will practice leadership skills such as assertiveness, decisiveness, persuasion, listening, and figuring out what is important to others.  Role play is intrinsically the act of putting oneself in someone else's shoes, this and other skills practiced in RPGs can help players develop their sense of empathy and compassion. Rarely outside of sports does play give people so much opportunity to hone their teamwork and social skills.