I understood you could substitute a BL or an Atkins bar for a S&S bar as long as they were the meal replacement bars and not the snack bars. I have certainly used them, and still do, with no ill effects and I know a few others on here have also used them. I love the berry fudge one and find they add a bit of variety which helps keep me focused. Some of the Atkins bars are lovely too - especially the chocolate orange one.Just as an aside - if anyone does like to use the BL bars, Approved Foods website is selling the berry fudge bars (a bit out of date but taste fine) for 4 for £1 instead of over £2 for 1 bar normal price.Good luck anyway!