[fjabre]

They are opposites. You want to get bigger or maintain muscle mass and simultaneously you want to fast (get smaller) and lose mass. Fasting will definitely cause you to lose mass - some fat and/or muscle.

While working out or lifting will cause you to increase your need for calories and food intake. They are opposing forces. You cannot have it both ways.

Fasting = less mass less food intake. Lifting/muscle mass = more food intake more mass

[godshatter]

Fasting doesn't imply eating less (on a larger time scale). You can, for example, eat the same number of calories all at once or spread out over the day.