the diet is set up to also help with insulin levels, so it is important to have the grapefruit but I have substituted 4oz of unsweetened juice instead of the grapefruit iteself.
Also, it is only 3 days, more of a cleansing sort of thing and a jump start to help you get going on losing weight and water...
it takes longer then 3 days for your body to hit starvation mode, but you body definately after time gets used to what you put in it, whether it be a lot or not enough so you have to give it a chance to get used to your new ways ...often plauteau's will come and then you have to alter things a wee bit to kick start the body back into gear of losing...
our bodies get used to being heavier and don't always want to let it go as fast as we would like...but it comes with time and dedication.
you can alter some things on the 3 day, but try and follow as close as you can as the foods put together are done so for a reason.
3 day question 
