Reducing for loop number

I would like to reduce the number of for loops since it takes a long time to run this piece of code.

 [~ , mm] = size(predictors); 
    prob = optimproblem('ObjectiveSense','min');
    x = optimvar('x',order+1);
    prob.Objective = 0;

    for j = 1:mm
        k = length(residualActual{1, j});
        for i = 1:k
            w = length(x);
            temp =0;
            for z = 1:w
                temp = temp + x(z) * predictors{1, k}(i,z);
            end
            prob.Objective = prob.Objective + (residualActual{1, k}(i)  - temp).^2 ;
        end
    end