What type of routine and diet for middle-aged/overweight people?

[WalkingBeast]

Hey everyone!!! Im planning on starting personal training shortly, and since I dont specialize in this type of thing (training and diet for middle-aged, overweight people), I thought Id get some suggestions from everyone here. Ive read many routines and diets, but Id like to get some feedback and see whats worked the best for you or your clients. Most of my clients will probabally be of this type. What kind of routine and diet would be best? Any feedback is greatly appreciated!!