Why is it I have read so many times that the key to fat loss is jogging/cycling/whatever LSD for long periods of time?
OK. When you lift weights to build muscle, when do you build the muscle. When you are lifting the weights, or during a recovery period?
During the recovery period.
When you perform a lot of LSD style work, you are gradually switching over to using fat as a source during exercise, but there is no persistant elevation of metabolism or hormonal/enzymatic activity afterwards.
When you perform hard interval style work (which can be classic sprint/jog protocols, tabatas, many timed WODs, and stuff like that) you are not using much fat as fuel during exercise, but the elevations in metabolism and in levels of the enzymes use for fat burning and appropriate hormones are significantly higher for a much longer period of time.
This is what is called "Afterburn", EPOC, or "Turbulence".