adjustment

Yes! I'm assuming you mean your body weight setting here on mfp? As you lose weight, your body needs less calories to maintain your new weight. Which is why you adjust the settings as you lose. Also, as you lose weight, you'll find that you won't burn as any calories doing the same exercises. The lighter you get, the less your body needs and the less you burn. It's not much, for me, it's 20 calories less for every 10 pounds I lose. (I think I'm remembering right)
As you get closer to your goal, you'll be finding it harder to lose the fat. This is also why there are so many setting on pounds per week to lose, I think it lets you pick from half a pound on up to 2 pounds per week. As you get closer to goal, you (and I) will be needing to switch to lower amounts per week to lose as it will get very hard to lose 2 pounds per week up to the end.