Hey IF newbie here. Have done VLCD before to no lasting success. Was going to do slim and save because I want to get this weight off faster and nomal healthy eating/working out doesn't work for me. Just wondering if anyone uses VLCD products for fast days? And can anyone explain the science behind why women only have 500 calories and men have 600? Read Moseley's book and it's not justifiably explained imo. Especially when on some VLCDs like S&S the amount of calories are based on your weight and bmi rather than your gender? I weigh almost as much as my OH plus I'm very active so wondering what difference 100 calories make per fast day?