you should but i know for some people they really slow weight loss down. I thought we were limited to one bar a day (would be great if we aren't because I know what I will be moving on to). Alongside are you drinking enough water. You need to be drinking the recommended amount 4 pints/2.25 land adding in all the fluid you would be getting in your shakes. Just checked in my book (its an old one though) and it says after 2 weeks on shakes you can swap one shake for a bar per day(doesn't give a reason why only one) but to drink an extra 1/2 pint of water.