Early on in Keto I believe the most important thing you can do is to not limit your fat intake. Next some mild limits on protein, but control the carbs. During this period I believe I lost close to 35 pounds of water.
It can be really hard to transition you body from a glucose based engine to a fat based engine.
For me, I went a month with no limits on fat and protein then I went 8 weeks limiting protein and some limits on fat. It was brutal. After this the weight has run off consistently at 3 pounds per week.
I believe that 8 week period represented my body burning thru the glucose stores and then being in withdrawal.
I have taken up my watch 1/2 inch since this started and it is still loose.