This is a good question. Here’s my take that might help you in making your personal decision.
The positives of doing a full 6 week round all at once is that, you only have load and purposefully gain weight to then lose the first day or two of vlcd once, you only have to go through the first few days of sometimes having detox symptoms (headache etc), and you only have to through the transition into P3 and the weight volatility that goes with that once.
The potential negative is that many of us start to hit a mental wall as we get into weeks 4-6 – where the diet begins to feel really hard, and our weight loss might be a bit slower in the middle of the round and it feels not as worth it to us. This is a time when no matter what our “plans” were, we might find ourselves cheating or really struggling to stick to the diet.
So the positive with the 3 week round is that you get to stop before the diet becomes unbearable. BUT the downsides are all the other things I mentioned above that you now have to go through twice.
I think IF you can handle a 6 week round, that in general this is the route to go. But I also think that you should give yourself leeway in your mind to stop at 3 or 4 weeks if you want to. My final round of hCG, I had not intended on doing a 6 week round. My plan was for 3. And indeed as I was in my 3rd week, the diet was feeling verrrrry hard. But then as I was getting ready to do my last injection….my period started. And guess what? I felt SO much better. Suddenly, I felt like the diet was not nearly so difficult afterall and it felt a lot more doable again. So at that point, I decided to continue. And I did the 6 weeks.
But for me, it was really important to feel the freedom to quit at that point if I felt I needed to. I would have felt really trapped in a corner if I was telling myself I had to do the 6 weeks when at that moment I was feeling so miserable. For me, this sort of trapped feeling leads to cheating, it really does.
So if you do your first 3 weeks, and you are still feeling like “this is doable. I can do this” – continue! However, IF you are at the end of the 3 weeks and you are feeling really rundown and miserable- then it’s probably better to take that P3 break and do another round when you feel more energized and ready again.