A week without loss is not really a plateau. Normal fluctuations in your weight happen all the time and often mask fat loss. For example, if you lost half a pound of fat last week, but retained half a pound of fluid weight, you would not see any loss.
Fluctuations can happen for a wide variety of reasons, many of which are out of your control - exercise, dehydration, sodium intake, hormones, even the weather can cause fluid retention. The food that you eat has a considerable amount of weight to it too, so how much of it sits in your digestive tract at a particular moment also affects your weight. So it's pretty typical for ordinary fluctuations in your weight to temporarily mask fat loss on the scale.
So, what to do? The only answer is patience. You have to wait long enough for fat loss to become clear over of the noise of these fluctuations. At a low starting weight already, you may not lose more than a half a pound of fat in a week, or a pound at most. So you might have to wait 2-4 weeks to really resolve your fat loss on the scale. It happens to everyone; it's part of the process.
Try to remember that what matters is not whether you weigh less today than a week ago; look at a longer time scale, like a month or two. Stick to your plan regardless of these fluctuations, and give it time.
High weight: 275 (August 2009) *** Low weight: 155 (October 2012)
Today, working off a partial regain. Current weight: 189.
* Make the best choice I can make, with every choice.
* Remember that the temptation in front of me is not the last of its kind that I will ever see; say "I'll pass today."
* Say "no!" to my whiny inner five-year-old.