Although no expert, the research i've read states unequivocably that when you do not eat at regular intervals, the body decides it is starving and converts all intake into fat. As the others have said, eat every meal and in between times as long as it's healthy and not mickie d's. That lets the body know you aren't starving, the metabolism will perk up.
With your limited eating system, you may well be nutrient deficient. This complex system we reside in needs all the necessary nutrients for optimal health. Fad diets are a prime example of unbalanced and unhealthy nutrient schemes. Anyone on a fad diet needs a quality broad spectrum multi vitamin with all essential nutrients. The one we're on has 178 ingredients which is just about top of the line!
Good luck and good health!