I am new to this board, so I am not sure if you have been introduced to the hormone "leptin" yet, but it is what is primarily responsible for "starvation mode".
It is far too complicated to do an exhaustive presentation on but I will give some basics as well as some places to go to learn more.
Basically, leptin is an endocrine hormone, a cytokine, specifically, secreted by adipose cells that tells various other parts of your body whether you are in a "fed" or "starved" state. It mediates this both short and long-term -- the former primarily by calories in vs. calories out, and the latter primarily by the amount of adipose tissue you have.
Eat a lot, specifically, eat a lot of carbohydrates as it is glucose metabolism that is the signal for the adipose tissue to produce leptin (or get fat) and leptin levels are high (as are anabolic hormones such as insulin, IGF-1, GH, testosterone, and T3 as well basal metabolic rate). Diet, and the vice versa occurs.
So, just adding protein is not the answer. The answer is to start periodically overfeeding (high carb, low fat) for 12-48 hours. Basically, what people call a "cheat day" -- only now we know why they work, so we can refine them to maximize results.
Here is a link with a bit more info -- click on the Q&A link and go down the page about half-way:
http://www.avantlabs.com/big_mfr_issue_2.htm
The best source would be to do a deja search for the word "leptin" in the Misc.Fitness.Weights newsgroup with "Par Deus", "Elzi Volk", or "Lyle McDonald" as the author. We have discussed it in great detail there.