Why 810 after 12 weeks SS

Please could someone let me know why it is neccessary to go onto 810 for a week after 12 weeks of SS. I know the government reccomend this, so CD have to follow it, but why do the government reccomend it? Do people find it difficult to go back onto SS after the week on 810?

Im not sure why the government recommend it but I was told that I need to step up to ss+ for a week(not 810). anyway, I pretty sure it has to do with not burning up lean muscle mass and boosting the metabolism for a week. After the 12th week of VLCD the body tends to start burning the mucsle. I am not an expert and Im sure someone will be along shoertly to explain it better. Doesnt your cdc know?(actually come to think of it, mine never told me why either hhmm)