Whoop, biochemistry is my specialty, I'll be graduating in 2010 so I hope I can clear something up.
Everybody is correct, an anabolic pathway is strictly "building something" to release energy, and a catabolic pathway is "breaking things down" to release energy.
Specifically in our (T-Men) interests is regarding muscle tissue/fat cells.
Glycolysis occurs 24/7 in humans unless you're trying to enter a ketogenic state... it's just the simplest form of carbohydrate catabolism, and it sucks at that since it's the most ancient energy pathway we have and mitochondria have 100x faster rates of creating ATP.
The catabolism of muscles and fat that we are talking about is actually glucose anabolism... if that makes sense. It's what happens when your body is lacking in glucose.
Specifically it's called "gluco-neogenesis", which basically means "creating glucose". The human body can create glucose from any citric acid cycle intermediates (any amino acid), and odd number fatty acid chains. It cannot use lysine and leucine (BCAAs anybody?).
So basically, when you're out for a run.. your body runs out of carbs. It starts to break down triglycerides to get some gluconeogenesis started. AT THE SAME TIME, it will use amino acids to create even more glucose because the two pathways are not mutually exclusive.
I hope I've answered the issue, maybe there's something I didn't cover. Basically you cannot be anabolic in terms of gaining muscle, but lose fat at the same time.. because the amino acids to be used in muscle synthesis will be sucked up by the gluconeogenesis pathway EXCEPT for leucine.
One more reason for us to pray to the almighty leucine.