I was really skeptical about this at first, but after doing a lot of reading and seeing great results from people doing it I think I'm going to try this on a few plants.
Now this if my first MJ grow, but I'm very familiar with plant biology, and when I first read about defoliation I thought that it would be the exact opposite of what you would want, based on what we know about plant growth and photosynthesis.
Why would you want to remove fan leafs when they are the essential powerhouses for most of the plants growth. But the more I think about it the more I think there may be some other action, hormonal or otherwise taking place by the removal of the leaves. The plant is cut off from what nature has designated as it's primary photosynthetic site, but MJ is a resilient plant, and clearly can draw from other sources to offset the damage. But you are playing god in an indoor grow, so as long as every other need is met I think it could be beneficial. Besides, who knows what effect these released hormones could have on flowering and bud development?
This is kind of a crude analogue, but I think it represents just how often organisms have to come up with alternative means to continue homeostasis. Think about when you cut yourself, you have a visible laceration for a few days then a scar forms (cutting the fan leaf), during the time that you have the scar it is structurally different than your skin but it serves the same purpose (the still growing defoliated plant). In the end, you probably won't even be able to tell that the scar was there in the first place, and the end result is the same if not stronger, thicker skin (the plant producing dank buds still in the end).
Hope I got what I was trying to say across effectively, just finished toking on some NL, needless to say, I'm sufficiently ripped
