I'm in the process of restructuring my diet and I was wondering:
Should different macronutrient ratios be used when bulking as opposed to cutting?
Right now I'm doing 40% protein, 40% carbs and 20% fats.
Are there any studies that suggest an optimal p/c/f ratio for muscle gain or an optimal ratio for fat loss?
Percentages are okay to get a general guideline, but it's more accurate to base your intake on your body weight.
If you're looking to cut I would say at least 30% from fats.
See, the problem with fixing the ratios to total calories is that you're fixing them to something that varies depending on whether you're bulking, cutting, or maintaining.
I suggest you fix them instead to your LBM:
Protein: at least 1.0g/lb LBM
Fat: at least 0.5g/lb LBM
Fill the rest of your calories with whatever combination of protein, carb and fat makes you comfortable.
I carb cycle, and I like my protein at around 1.7g/lb lbm and fats at around 0.7g/lb lbm to 0.8g/lb lbm most days. You'll find the levels you like for your own body.
Some like to fill the extra caloric requirement for bulking with just extra carb, or just extra fat. Some like to increase everything. On a cut, I concentrate on the fat and protein calories, since these are the most satisfying.
If you go to my cutting diet link in my sig, there's a link on that page that gives a reference to why 0.5g/lb lbm is good for test production.