Just started P90X 4 days ago and I'm just a bit confused about how much I should be eating. I'm not a big guy at all, 5'6" 124 pounds. I guess I might be in the minority here because I'm doing P90X to get cut rather than losing weight lol. If I had any sort of fat it would be a bit of a gut and that's about it. My question is should I follow the fat shredder phase or should I be eating more calories in general? Any help would be appreciated.

Im in the same boat as you. What i am doing is basically just eating healthy foods and trying to hit about 35-40% protein and carb and 20% fat in diet. Im on my 3rd week and so far so good i guess.

It says in the nutrition manual that you don't need to do fat shredder for the entire phase 1 if you do not have fat to lose. I'd say if you're under 15% body fat, I'd go directly to the phase 2 nutrition plan. If you still want to lose the fat, but gain weight, you will need to eat more calories in general. I'm not an expert, but if I had to put a number on it, shoot for 1800-2000 calories a day; 20% fat, 30% carbs, 50% protein. Do that for a week, if you gain weight, then you're doing it right, if you lose weight or stay the same, you need to add even more calories.

Thanks, a friend of mine also told me to up my carbs intake as well. I'll see how I do with that minor tweak in my diet.