Quick one for you lifters out there!

Just weight, chances are running with a stomach full of protein won't sit well.

i run after i lift, and honestly, i couldn't run with a protein shake roiling in my stomach.
i am looking into amino acids though - as i understand it, they are taken during workout (mixed in your water) and are much easier digested than protein. - this is where someone with actual knowledge ought to chime in... :-)

From what I've read, there's a window of increased protein absorption immediately following a workout - doesn't matter if it's high intensity cardio or lifting. Personally, I wouldn't want a stomach full of protein shake for my runs, but it's up to you.

I agree that the timing of the meal is probably less important than the amount as long as it doesn't make you sick to your stomach.

But 45 min of cardio counts as "a lot" in my book. Is it fairly high intensity cardio, such as running, or more along the lines of casual pedaling at 75 rpm on an exercise bike? There is some controversy as to what fasted cardio does to your strength gains and metabolism. Here are some starter references:

http://alanaragon.com/myths-under-the-microscope-part-2-false-hopes-for-fasted-cardio.html
http://www.bodyrecomposition.com/fat-loss/fasted-cardio-and-fat-loss-qa.html
http://www.leangains.com/2010/04/leangains-guide.html

As for me, I split my cardio and lifting so I don't do both on any given day. I just can't spend that much time a day exercising. I have to leave some free hours in my day to waste on MFP.

I too would want to split this up to different days. You want to have enough energy to give good effort to your workout, versus taking it easy through your weights workout so that you have enough left over to get your cardio in. The object is to have quality workouts, not just long workouts.

I'm really not sure how I feel about the topic. You'll see articles posted everywhere about how it doesn't matter and a lot of that leads into support for Intermittent Fasting. I've personally worked with John Meadows on my diet and read pre/post workout nutrition articles from other leading experts (John Berardi, Shelby Starnes, Lonnie Lowery) in the field as well about eating before and after. Having tried both IF and eating before / after I can only tell you what I feel works best for me. On IF my workout were okay but sometimes I definitely had a lack of energy. I also felt like I started to lose a little strength and muscle mass over time. I hit my calories and macros every day during the process. I later went back to what John had me doing which is a big shake with carbs, little fat, and protein prior to working out and then some protein and carbs post-workout with some of the carbs being something hi-GI that would get my insulin level up. I've actually been keeping at the same calorie and macro-targets but I'm down 7lbs, definitely a little leaner, and my lifts are finally back-up again. There have been a couple workout sessions where I had a big late meal the night before and I wakeup feeling full and just have some whey prior to working out. If I'm doing a cardio only session, I will still do that fasted.

Is this a false positive for some reason, possibly but I'm not sure what it would be. I only know what my results have been over the last three months. I don't feel that either style (Fasted / Un-Fasted) is better than the other; I think it really comes down to the individual. My GF doesn't eat before she works out or plays soccer because she would get sick during her session and she does just fine. Just my two-cents on this subject.

I asked my trainer this exact same question- as I do about 30 mins of cardio (rowing and stairs) immediately following our session.
His response (and I trust him implicitly) was that I should wait till I was finished.
For mostly the same reasons as expressed already, so I thought I would add weight to the issue (no pun intended).

- stomach will be busy digesting, blood goes to stomach rather than muscles that are still working, fatigue kicks in and therefore cancels out what I am trying to accomplish.

Just hit your macros...for the vast majority of us, the timing of protein intake is pretty irrelevant. If you were a competitive athlete looking for any possible edge, I would make a very slight difference.

I equate it to having a really awesome set of golf clubs...for most of us, it's really not going to make a hill of beans difference in our overall performance...but there's that small minority for whom it's going to make or break.

This....focus on your macros