If you do intermittent fasting (16-24h), you can eat it during the non-fasting periods and it should help with muscle loss. Also, you can do HIIT during longer

If you do intermittent fasting (16-24h), you can eat it during the non-fasting periods and it should help with muscle loss. Also, you can do HIIT during longer fasts to keep muscles "in demand" so that proteins aren't recycled by your body to usual extent. There was some study about it somewhere...