Fast burners tend to process their food rapidly, often with high energy and strong mental function. Fast burners often don't enjoy sweet desserts, but prefer fatty or salty snacks. Although they may have a strong appetite and prefer several large meals per day, digestive processes may actually be somewhat weak and inefficient. These fast burners may need frequent feedings to prevent energy crash and low blood sugar problems. The other main metabolic type are the slow burners.
Slow burners tend to like sweets but generally are unconcerned with food and eating.
The metabolic approach may offer some help in understanding why some individuals have followed one or another approach diligently and not gotten good results. Perhaps the diet they chose was not suited to their metabolic rate, and so did not offer the benefits which others experience. If so, it's understandable. If after all these differing opinions and concepts aren't enough, let me mention a couple of other things to be considered when developing your own personal diet. Ancestry and the genes passed down to us from our parents also contribute significantly.