If only losing body fat translated to carrying an additional amount of equal weight like that of a rifle but really they have no relationship. Now your idea of lightening a tent or sleeping bag, now that makes some sense. A rifle is without question the most awkward weight a person will carry and lightening a rifle is without question the simplest means of reducing fatigue on back, arms, etc but I'd agree that putting up with a couple extra pounds in a rifle that is well suited to sheep hunting is worth it but there really is no way to compensate other than with more effort. Nothing is free in the mountains.