I started my high protein diet on 12/21/11, it has been brutal! the first few days I had headaches, light-headed, was cranky and tired and starving! After those days passed it wasn't so bad, I increased my shakes to 3 a day as recommended by my doctor and increase my veggies and that help a lot. Also I took an extra walk a day and that really helped, something about the protein not just sitting around and actually being used.