Most video games completely ignore important elements like weight. For some reason, characters can carry an incredible amount of equipment in their backpack. Only a few games actually let the factor of weight influence the gameplay (e.g. Dark Souls).
No soldier can carry more armor and auxiliary equipment than what their physique allows. Current British and US soldiers use the Modular Lightweight Load-carrying Equipment system, also known as MOLLE. It was specifically designed to help soldiers define the necessary amount of equipment they could carry during their missions without overburdening themselves.