Running (depening on how fast, and how long) can be extremely catabolic for LOTS of people. If you have problems gaining mass DON'T run unless your sport (if in any) demands it. I am running because at my stage of the game I am more interested in overall health than extreme size. I have been 270 before, and its just a lot of work and and my overall conditioning at extreme bodyweight for me was ****ty. I run 2-5 miles (usually 2-3) twice a week and pull a sled a couple time a week also.
For fat loss on any kind of routine you want low intensity cardio at a level you can carry on a conversation while doing. This level is NOT catabolic for most people and works wonders for reducing bodyfat. I used to do keto diets, but now only do timed carb diets. if ultimate mass is your goal, you will leave the running alone.