In Tim Ferriss’s blog post (The 4 hour work week guy) “How to Lose 20 lbs. of Fat in 30 Days… Without Doing Any Exercise” he talks about taking a day each week off from your diet and eating calorie rich foods to “ensure that your metabolic rate (thyroid function, etc.) doesn’t downregulate from extended caloric restriction.”
I also found that taking a day off each week allows me to use that as my cravings exorcism day (The day I get rid of my craving demons). The free day is when I eat what I craved all week without guilt and without going off the program. Not feeling guilty goes along way in staying on a long term program.
Tim’s other suggestions on keeping your carbs low and starting your day by consuming at least 30 grams of protein within 30 minutes of waking up (This is so your body can start the day with the right fat burning hormones) are powerful ways to get and stay thin.