7lb in 4 days!!

I'd honestly say not to take this the wrong way, but it could be water weight.

Water weight or not, you're likely eating too few calories. 1200 is the bare minimum you should generally aim for. If you eat this way for too long, your body won't be getting enough fuel to properly work.

for whatever reason, usually when I start, I drop quite a bit of weight in the first week or so and then it tapers off to a much more reasonable rate. I'm not sure of the mechanism. Being that 3500 calories is a lb, I certainly don't think I'm running that kind of calorie deficit. I don't know if maybe my metabolism in overdrive mode, since I was feeding enough food for 1 1/2 people. Otherwise I think it might be water weight, but I'm not showing any signs that I'm dehydrated at all. So in any case, I see the same thing that you do at the start.