How do you other trainers get clients to make small changes in eating habits?
I suggest that you make small suggestions each session. But in a friendly way non-judgmental manner. For example have you tried the whole grain pasta it taste just like the white pasta except your body burns it faster. Also having them keep a log for a week of their eating habits is a eye opener for them. As opposed to you lecturing them they can see for themselves how their diet is undermining their progress.