I did quite a bit of reading into fasting and muscle / protein loss, to the point of saturation. Here are some links with the messages I took away from them....
In http://jp.physoc.org/content/590/5/1049.long "Muscle protein synthesis in response to nutrition and exercise" it is stated that increased muscle protein synthesis (MPS) occurs on feeding with protein due to increased amino acid availability. "Nutrient-driven increases in MPS are of finite duration (∼1.5 h), switching off thereafter despite sustained amino acid availability and intramuscular anabolic signalling." - in other words the post-meal muscle building period is finite, although extended by resistance exercise at high load. A maximum useful dose of 20g of protein is suggested as providing sufficient amino acids to sustain MPS after eating - any more can't be used in the time available.
SKELETAL MUSCLE METABOLISM IN EXERCISE AND DIABETES Book Series: ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY Volume: 441 Pages: 307-319 Published: 1998 says that "Muscle proteins turn over slowly and there are minimal diurnal changes in the size of the muscle protein pool in response to feeding and fasting. Nitrogen balance and tracer studies indicate that protein oxidation and net protein breakdown (degradation - synthesis) is not increased during dynamic exercise at intensities of less than or equal to 70% VO2max."
http://www.ncbi.nlm.nih.gov/pubmed/9240936 is a useful overview...
"A continuous turnover of protein (synthesis and breakdown) maintains the functional integrity and quality of skeletal muscle. Hormones are important regulators of this remodeling process. Anabolic hormones stimulate human muscle growth mainly by increasing protein synthesis (growth hormone, insulin-like growth factors, and testosterone) or by decreasing protein breakdown (insulin)."
http://jn.nutrition.org/content/130/7/1868S.full "Dietary Protein and Nitrogen Utilization" includes a graph showing that the turnover of body protein per kg of body weight is much higher than the protein intake :
http://jap.physiology.org/content/106/4/1374.full has more about timing of food relative to exercise and effect on protein synthesis.
http://www.ncbi.nlm.nih.gov/pubmed/6408111 "Whole body protein breakdown rates and hormonal adaptation in fasted obese subjects." reports that the breakdown rate after 7 days of fasting is reduced from the 1.96 g/kg.day of a 12-hour fast to 1.54 g/kg.day.