Most people I see fixated on 5 pound rifles could easily stand to lose 10 or more pound and get in better shape.
A truer statement has not been made.
I've seen guys spend hundreds, if not thousands of dollars to drop ounces on a rifle or binos, when it would have been more practical to put down the Snickers & Coke.
You nailed it.
As soon as I start carrying my gut around in my hands all day, I'll give that some credence.
I gotta respectfully disagree with you on that one just based upon my own experience.
I'm physically my best at ~195 lbs, running and lifting about four days per week. I had the unfortunate experience of letting my weight drift up to 230-235. Although my legs were still strong from the running, I fatigued much quicker and it was definitely easier to become winded just carrying that extra weight.
Regardless of rifle, be it a Kimber Montana or a Sendero, I don't notice rifle weight like a do extra body weight, but as steelhead mentioned, I do quickly notice the weight of my boots. YMMV.