If Sestrin administration truly prevents muscle atrophy, it could commoditize fitness. People would train intensively for a year or two and then take Sestrin for the rest of their life. Everyone would look like an Olympian. That would also single-handedly solve obesity, since baseline caloric requirements would shoot up. Perhaps Sestrin would even negate the need for cardio, by maintaining a strong heart. Quality-adjusted life years and overall lifespan would improve. Lastly, it would be interesting to see how people modulate their musculature just like how they choose their clothes. People would self-select into a conspicuously identifiable group of similarly-shaped people.
Of course, I’m skeptical that Sestrin might fully prevent muscle atrophy on its own. At the same time, there’s no evolutionary reason for us to lose muscle anymore, since calories are essentially guaranteed. Intuitively, muscle atrophy seems like a puzzle that can be solved. If the muscle is already there, find whatever phenomenon makes it wither and stop it.