The short answer is: Higher carbohydrates are usually recomended for athletic performance, and deservingly s. Athletes use the glycogen that carbs provide. 45 minutes of weight training alone does not nearly deplete glycogen as would 45 minutes of wrestling or sprinting. Physique modification is where higher protein comes into play.
If you are an athlete that needs to modify your physique then the following applies.
I'm going to go into protein to back into the support for why high protein is the approach for physique modification.
While the International Society of Sports Nutrition reccomends protein intakes of 1.4 Ã¢?? 2.0 g/kg/day (.6-.8 g/lb/day) for strength and power exercise, keep in mind these figures are not for body recomposition. I personally feel this number is minimum end of the range if the goal is body transformation rather than strength and power exercise.
I would propose that for the purposes of body recomp protein is not used to just keep nitrogen balance positive, but nitrogen balance must be drastically positive. To this end the calories from protein is just a means to an end. and I suggest 3.3-4.4g/kg, or 1.5-2 g/lb, should be used. The remainder should be from fat and carbs.
If an excess amount of calories is consumed (goal = bulking), there are studies showing less protein is needed for positive nitrogen balance. However, unless you are sub 10% bf stick with 2 g/lb/day because it is likely that you are not sensitive enough to insulin to handle the excess carbs, and eating enough excess calories all from fat would not be ideal.
Based on 10% excess calories**:
Protein: 2 g/pound
Carbs & Fat: Between [~2.4g/pound and ~.4g/pound respectively] & [~1g/pound and ~1g/pound respectively]
** assumes an athlete ~15% BF and exercise is ~1hr free weights (adjust macros accordingly for lbm and exercise)
If you're in a calorie deficit (goal = cutting), also stick to 2 g/lb/day to keep nitrogen balance as high as possible.
I hope this helps.