If you have been dieting or competed in a bodybuilding show and are now ready to focus on gaining muscle mass its important to transition properly so you don’t gain too much unwanted body fat. After a diet or contest your body is primed to gain muscle if done correctly, but it is also very easy to gain unwanted fat. Following a hypo-caloric diet necessary to lose body fat for an extended period of time will result in a slowed metabolism through various mechanisms. If you switch gears and go straight into a large hyper-caloric diet you will almost certainly gain unwanted body fat. A good strategy is to go into a maintenance or just slightly above maintenance phase for a couple weeks by increasing carbohydrates first and healthy fats secondly if you where dieting on a low fat diet (note if you just competed your weight might still go up due to water retention). Protein should have remained high throughout the diet and possibly even increased so protein should stay the same or even go down some initially if consuming much more then 1g/lb body weight. After a couple of weeks while your metabolism wont be back to what it was yet before the diet, it will be in a better place to start adding muscle mass without the unwanted fat gain. From here I generally recommend adding 250-500 calories (women the lower end men closer to the upper) initially again mostly from carbohydrates and healthy fats at least until you reach about 20% of your diet from fats or around 0.35g/lb. From there access how your doing every couple weeks and continue to add calories as needed. I generally add my additional calories from carbs once I reach 0.35g/lb body weight from fat and 1-1.5g/lb body weight in protein.
During a mass phase its important to monitor body fat levels so they don’t get too high. You can’t stay contest shape lean while optimizing your muscle building potential. However if you allow body fat to get too high this isn’t good either. Men should generally not allow their body fat levels get above 8-12% as any higher then that makes it much more difficult to get back into contest shape. For women it more around 16-20%. Not only is it harder to get back into contest shape when body fat levels get too high but adding muscle mass becomes more difficult as insulin sensitivity drops and estrogen levels tend to go up causing a shift in partitioning that favors fat gain over muscle gain. If you notice your starting to put on body fat cut back to where your still adding mass but at a slower rate without the fat gain.
If for what ever reason while bulking you allowed your body fat to get above acceptable levels I suggest doing a mini diet for 4-8 weeks followed by a 2 weeks maintenance diet before resuming your mass phase.