I'm sure that there are a few factors that figure into that equation. If you are a lineman, this could be true. If you are a lean, muscular player that Ricky is/was, during the first year, you lose muscle mass and, as TT has pointed out, you have a rapid drop in weight (due to muscle weighing more than fat). Now, if this kind of lifestyle goes on for extended period of time, THEN you will begin increase stores of body fat and in turn gain weight. Ricky was in great shape and has lost muscle mass. Since he's been studying Wholistic Medicine, I would venture to say that he has stayed away from foods that are not conducive to his new way of life (in other words, he's been eating healthy). For these reasons, I am not surprised that he hasn't packed on the pounds during his year off.
For those that think the weed should have caused him to gain weight, this is not true. Weed actually acts as an appetite suppressent in many smokers.