Drinking lots of water helps raise your metabolism. So does eating small
meals throughout the day. I eat about every two hours, and I can lose
weight eating 2,500 kcal per day, at 5' 10" and 185.

This is because of the cals required to digest & break down food, eating
several times a day is 'energy-inefficient' for the body (as opposed to one
or two big meals), the equivalent of going to the shops every time you want
to have something to eat or drink instead of stocking food & drink at home,
you'd use more energy fuelling your body and/or car doing this.

It all comes down to calories in vs. calories out. What Ignoramus said is
correct. Your metabolism will slow to some degree. But, that's normal.

You can add a "re-feed" day in your week as I do. I've been told it helps
reassure your metabolism that it's not going to starve, so don't slow
down. Also, dieting with out a re-feed day begins to suck after awhile.
You still need to enjoy life.

I posted about refeeds a while ago, although some people had arguments
against them, I had several refeeds, every 10-15 days. I was worried about
cancelling out the effect of the calorie restrictive days but, to my
surprise, even eating up to 3,500 cals on such days didn't seem to affect
the weight loss at all. There are psychological reasons for them (like you
say, life sucks without them) but as far as your body is concerned, you seem
to need them more if you restrict calories too far on your diet days and if
you're not really fat.