I didn't and haven't used any restricted products. For me, and each answer will be from a personal perspective, I lost about 4 pounds a week for 10 weeks. Some people have used restricted from the beginning without issue. You can do this one of two ways. You are paying a clinic for food and guidance, if they don't have a problem and they will sell you the restricted items (my coach won't) you can use them. If the clinic won't sell them, then you need to decide if you want them enough to order from somewhere else. As far as losing weight... it doesn't seem to effect everyone badly so, you would have to see how your body responds. To that end, you might want to have a week or two of non restricted so you can see if using restricted items does cause a slow down. If it doesn't, go for it in moderation. If it does effect you, wait and try again later.
Jordanna waited 2 months to add restricted items, has 1 or 2 a week now. She had great loss. I am not sure how bevs, or novak, or sylvie, or babs, or cw (chaplains wifey), sassy, or some of the other big losers did but, listen to their advice! They have had truly great success!