How to reduce the + operator memory consumption for self-defined class in C++?

I give the following examples to illustrate my question:

 class BigClass
{
public:
    static int destruct_num;
    friend BigClass operator + (const BigClass &obj1, const BigClass &obj2);
    std::vector<int> abc;

    BigClass()
    {

    }

    ~BigClass()
    {
        destruct_num++;
        std::cout << "BigClass destructor " <<destruct_num<< std::endl;

    }

    BigClass(BigClass&& bc) :abc(std::move(bc.abc))
    {
        std::cout << "move operation is involed" << std::endl;
    }
};

int BigClass::destruct_num = 0;

BigClass operator + (const BigClass &obj1, const BigClass &obj2)
{
    BigClass temp;
    temp.abc = obj1.abc;
    temp.abc.insert(temp.abc.end(), obj2.abc.begin(), obj2.abc.end());

    return temp;

}

int main(void)
{

    BigClass a;
    a.abc = { 1,2,3 };
    BigClass b;
    b.abc = { 5,6,7 };
    BigClass c = a + b;

//  for (auto& v : c.abc)
//      std::cout << v << "  ";

    return 0;


}   

One problem with regard to operator + is that we have to generate a temp BigClass object temporally and then return it. Are there someways to reduce this burden?