You know, at first I was really hungry. I had problems with concentration and dizziness.. but I didn't start with SlimFast, I started with something similar, RightSize.
Now I will say that about and hour and half to two hours after drinking a shake or eating a bar, I will start to get hungry. I know they advertise for hunger control for up to 4 hours... but it doesn't last like that for me. And keep in mind, everyone is different.
Because I was constantly thinking about food, I really had to tweak the diet to fit me and my body. Because I have so much weight to loose, I can afford to eat more calories than recommended on the slimfast plan, and still loose weight. I had read a book by Paul McKenna "I can make you thin" and he was explaining research that diets as low as 1500 calories a day is like mini-starvation... as researched during the holocaust... and causes people to horde food, binge on food, steal lie and cheat to get it. And to think there are MANY diets out there that are much lower than 1500 cals. a day.
I couldn't completely devote myself to the ideas in the book as I was having sucess with slimfast... so I took the main one.. eat when you are hungry. and started adding snacks that are healthy. For example.. and I eat this almost every day... I have a bar within an hour of waking at about 6:45am... (supposed to eat within an hour of waking.. really supposed to revv your metabolism).. I can start to feel hunger at 8am. Usually around 9am, I would eat a piece of string cheese (50 cals) but as i have found that cough drops have curbed alot of my hunger... (had a cold for about 2 1/2 weeks...gah!) I haven't been having the cheese.
At 10:30, I eat two rice cakes (70 cals) and have lunch around 12pm. Which is a shake and a sandwich (the states version for lunch is a shake and eat an additional 200 cals... which is normally half a sandwich, but because I use light bread, I can have a full one)
I usually eat anthoer piece of cheese around 2 and a snack bar around 4ish.. dinner at 6pm.
So you see (and sorry for the long post).. everone and every body is different.. and it is a process to find what works for you.
The first week of loss might be big.. 5 lbs or more, but after that it is a tyical 1-3 lbs a week. And I have recently started exercising, so yes, you can
LR