A person leans in the opposite direction when he or she lifts a heavy load in one hand.
I read a reason for the same in a book.
According to the book, if a body is placed on a horizontal surface, the torque of the contact forces about the centre of mass should be zero to maintain equilibrium. This may happen only if the vertical line through the centre of mass cuts the base surface at a point within the contact area or the area bounded by the contact point. That's why the person leans.
But I am unable to understand that how does it explain the leaning of person on lifting a heavy load.