Weight management in cats?

My cat will be 12 months old in April this year and he is overweight, i feed him on roo mince, Pro Plan Chicken and Rice dry and royal canin dental dry for his teeth. He get a small handful of mince twice a day and 1/2 a cup of the mixed dry to graze on during the day. I was thinking of switching him to Pro Plan weight Management dry only but still giving him meat. Is he too young to have weight management dry?