When you fast, restrict, or otherwise deprive and stress your body with fat loss, your body begins to immediately adapt by triggering a cascade of hormonal adaptations. Among these adaptations are mild hypothyroidism. This is known as "starvation mode".

Once you initiate a refeed, your body immediately begins to replenish its thyroid hormone levels to normal. This increases metabolism again.

So you see, by taking yourself down to low levels of intake, but then "jump starting" the metabolism with high cal/carb days, you avoid the adaption to starvation (hypothyroidism).

Here are some studies which offer some evidence...

http://jap.physiology.org/cgi/content/full/88/5/1820

http://www.ncbi.nlm.nih.gov/entrez/...1&dopt=Abstract

There's, I'm sure, lots more studies out there showing how fat loss and energy restriction causes hypothyroidism and other endocrine abnormalities.

Bottom line. If you're stalled and expressing symptoms of conservation (no energy, dry skin, shedding hair, zero libido & other indicators of fertility abnormalities)... try eating more. Eat more carbs and eat until you are stuffed for 1 or 2 days. See if that works.
I personally noticed during my weight loss (which was achieved mainly by restriction), on days where I would binge on meats were often the days I lost more soon after. Many people have also noticed this correlation. At first I thought it was psychological or behavioral or some other simple explanation, but I've now come to totally support and rally behind the theory that staggering calories (and carbs) really works for physiological reasons.