Chess improvement is no easy task. The food and diet model is a representation of the factors of chess improvement.
Here is the basic outline:
Tournament games (or correspondence games for a correspondence player) – this comprises of the main diet for the player; the player should not play too many tournament games or too few, i.e. eating too much or too little
Analysing your games and studying chess – this is sort of like digesting the food; if you keep playing and playing without trying to find out where you went wrong, your mind/digestion will become bloated with low quality information. Instead, a player needs to analyse his games in order to sort out the important information and discard the unnecessary information. Similarly, by studying chess, the player learns from the mistakes of the others, e.g. the author of a chess book, allowing him to cut down on useless data.
Blitz chess and slower online time controls – think of blitz as extra antioxidants, nutritional supplements or a healthy snack for your diet; blitz allows you to train your tactical vision under time pressure and also gives you a chance to practice your opening knowledge
Online bullet chess – this can be highly enjoyable or exhilarating but should be regarded as junk food; some occasional bullet chess is fine, but too much will be detrimental to your long-term chess