It's totally normal and likely won't be the last time you stall on your way to your goal.
The three-week stall is quite common for the following reasons:
After surgery, our bodies are filled to the top with fluid, both from some water retention before surgery and all the fluids they put into you at the hospital.
After surgery while on the liquid diet, most of us go into ketosis, which has a diuretic effect that increases the volume of the liquid you release (not necessarily the frequency, but amount). Even if you are getting your 64oz of liquid or more per day during this time, most of us are still on the slightly dehydrated side. So, during the first 2-3 weeks we lose a lot of fluid weight. It's not physically possible to lose burn as much fat equal to the weight that most people lose during this time.
Around week 3-6 most of us are adding in purees and soft food, and we are no longer in ketosis and/or we are catching up on our hydration. This decrease in urine volume and increase in hydration is a counter-balance to the fat loss, so people often experience a stall or a slight gain in weight.
I completely GUARANTEE that if you are following the prescribed post-surgery recommendations for food and hydration, your body is burning fat, regardless of what the scale reads. As long as you are doing what is recommended during this time, your body composition is changing.
There are other factors that come into play to create stalls, not the least of which is our bodies aren't designed to lose weight, they are designed to protect weight, and even though the surgery gives us an incredible weapon in the battle, our bodies still need to adapt and make adjustments from time to time. The key is to continue making good food choices, stay hydrated, and maintain a caloric deficit. Working in some resistance training after you are cleared to lift more than 15lbs helps reduce muscle loss and also has a positive effect on metabolism.
You will be okay. Stay on track and keep the faith in the process.
