This is basically a modified fasting regimen that allows you to re-adjust your metabolism back to the way it was designed to work. Specifically, it's called alternate day fasting. Here's how it works.
On fasting days, you reduce your food intake to 500 calories. This is the day (actually every 2nd day where you do need to count calories a bit.) These calories should be consumed at one meal; ideally lunch or dinner. On NON-fasting days (every 2nd day) you can eat whatever you want, without counting.
It's simple, but it does an extraordinary thing. You need to consider these mental/emotional perspectives before you begin this regimen and if you are diabetic or hypoglycemic or suffer from adrenal problems, discuss it with your doctor first, please.
Eating one meal on your fast day usually means not eating breakfast. Most of us believe that breakfast is the most important meal of the day. Researching the literature on this, you'll find that most of the studies done that support this perspective were funded by the cereal companies. Other, independent studies do NOT support the importance of breakfast over other meals.
The toughest time emotionally and mentally with this alternate day fast regimen comes in the first 7 - 10 days. It's during this time that your body is adjusting and re-setting your metabolism. This is the CRITICAL period of this weight loss regimen. Stop and think critically for a moment, please. Re-read the previous sentence with the word critical in it.