I don't know if it has been mentioned but BMI is bullshit anyhow. Muscles for example weight more than fat.
And Varabently, muscle is better because they bring stability to the bone and not just burden it. Sorry my english is bad, I'm from Germany. But if you exercise often, your heart muscle gets stronger too!
Oh and by the survival part, our bodies are slowly (take like 1000 years a step) acommodatin to our "city" livestyles.
And of course lifting 400 lbs (probably 200 kg?) once isn't great for survivability, it's more a fitness programm of strength and agility dense muscles not thick ones, even though that depends on someones genes.