I think it took about 4 or 5 months. I am on Tamoxifen, a post breast cancer drug and my oncologist was amazed. He said that people simply do not loose weight on Tamoifen, they gain. I lost weight when I was able to produce ketones in my urine. This is a sign that your body is in a catabolic state (eating its own fat for energy instead of what you are taking in.) This diet works better for people who aren’t as compromised as I am. A friend lost 30 pounds in the same 4 months and she only really stayed on the diet during the week. On weekends she ate whatever.