I know everyone is different based on activity levels, etc. but I'm curious what your calories are on both your cut and bulk. Also, do you prefer to do cardio during your cuts so you can eat more?
For maintenance calories I simply multiply my bodyweight by 14 or 15. I live in Michigan, so in the cold months I do x14. In the summer I am more active (cycling, kayaking, walking, yardwork, etc.) so I do x15.
For cuts I subtract 1,000 calories/day to lose 2lbs of fat per week (every 3,500 calories is equal to 1lb). I lift 6x per week, and find that this works good if I don't want to do any cardio. If I do add in cardio, I simply add whatever amount of calories I burn back into my diet (so if you cycle daily for 45 minutes and burn 500 calories each time, you would want to add in 500 calories/day of food). So, you can make adjustments based on hunger levels. The key is to never go over 2lbs per week... if you do you will start to lose more muscle than fat. If you notice you are losing a little bit too much muscle on cuts, you can cut it back to 1-1.5lb fat loss per week.
For example, I am 215lbs at the moment - so I would do the following:
- 215lbs x 15 = 3,225 daily calories for maintenance
- For cutting w/ no added cardio: 3,225 - 1,000 = 2,225 daily calories to burn 2lbs per week
- For cutting w/ 45min added cardio (each cardio session burns 500 calories): 3,225 - 1,000 + 500 = 2,725 daily calories to burn 2lbs per week w/ daily cardio
- For bulking: 3,225 + 500 = 3,775 daily calories to bulk/add 1.0lbs of mass per week
- For bulking: 3,225 + 750 = 3,975 daily calories to bulk/add 1.5lbs of mass per week
When I am cutting I find that the best way to know if I am holding or losing muscle is to measure my arms. For me I stay relatively lean so my arms never get much appreciable fat on them. So I know they should never lose much size at all - maybe 1/4" every 20lbs or so. The reason I do this is because when dieting, you tend to get a little flat. Expect to lose maybe 1/8-1/4" in size in the first week (and then use that number as a baseline), but don't be alarmed because it is just reduced water from eating less calories/carbs, so you really didn't lose anything. After that you shouldn't lose much at all. A lot of people think they are losing muscle when they are cutting simply due to the fact that they are 'flat'. The measuring tape trick helps me know if I am really losing muscle or not. (If your training volume decreases, you will lose up to 1/4" in size as well - just due to water. It will return once you get back to normal schedule.)