Wow I would have never thought to do green beans. How much should I give him? He is 9 ptwo pounds overweight and he has bad knees so they told me that its probably hurting him since he is overweight. I feel so bad

I want to try the green bean thing and hopefully it will help him out, are canned beans okay or are the frozen ones better to use? I bought some healthy treats, so I am starting to give him those, but I would love some recommendations.
Thanks!