Intermittent fasting is becoming quite popular as a weight control tactic. It involves narrowing your eating "window" to 8 or fewer hours a day.

For those considering combining IF with your stabilization 21 days of P3, here is why I think it would be better to wait until P4 to give this a try:

The purpose of P3 is to stabilize at your ending weight on P2 of the HCG diet. In order to do that, you have to eat the right kinds of foods (good oils, all proteins, non-starchy veggies and some fruit) and you have to eat enough of them. After P2, most people's capacity is small, and many struggle to get enough food in, especially the first few days. Intermittent fasting rules make that even harder.

The idea behind intermittent fasting is that having less time to eat will restrict your food intake. You do not want to be cutting back on food intake in P3.

Here is why:
At the end of P2, your metabolism is running at a higher more efficient level than previous to the diet.

You need to get in touch with your hunger and satisfaction signals so that you eat enough and often enough to keep that revved up metabolism burning. You are learning how to fuel your body during P3. Paradoxically, the biggest issue with weight gain in P3 is failing to eat enough. This is because the fear of regain is often very strong. But it needs to be overcome. You can trust the process. People are often amazed at how much they can during P3 and still stay in their 2 pound window.

Dr. Simeons said that in P3, eat whatever you like as long as you avoid starch and sugar. You have been given a great gift through the elimination diet aspect of P2---cravings will be gone. This gives you a rare opportunity to learn your hunger and satisfaction signals without cravings confusing the landscape. You need to learn how to eat enough, and to eat when hungry, not famished, as waiting too long almost ensures your will overeat. P3 is a golden opportunity to shift your food relationship to a healthy fuel-based focus where you recognize and address your hunger in time, and appropriately.

Delaying eating until later in the day interferes with your hunger signals. Every hour after waking that you delay eating, slows down your metabolism. This is counter productive to your P3 goals.

To keep your metabolism humming in P3, try to get some calories in you within an hour of awakening. It doesn't have to be a lot, but it needs to be nourishing. Something with some protein and a little fat. It could be something like coffee with collagen and MCT oil. (Froth it with a little sunflower lecithin---it gets very creamy), a small protein shake, or if you can handle solids-- some full fat cottage cheese or greek yogurt and berries, or a couple strips of bacon and some avocado. This little calorie boost early in the day wakes up your digestive system and you are off and running.