This involves fasting every other day, either by reducing calorie intake to 25% of normal on fasting days or by not eating any food at all. Alternate day fasting is a form of intermittent fasting that involves alternating between days of normal calorie intake and days of very low calorie intake.
There are different variations of alternate day fasting, but a common method is to eat normally on one day (usually defined as consuming 100% of daily calorie needs) and then limit calorie intake to around 500-600 calories on the next day (usually defined as consuming 25% of daily calorie needs).
For example, on a normal calorie intake day, you might eat three meals that add up to 2,000 calories if that is your daily caloric need. On a low-calorie intake day, you would eat a small breakfast and a small dinner totaling 500-600 calories, and fast for the rest of the day.
During the low-calorie intake day, it is important to choose nutrient-dense foods that provide the body with essential vitamins and minerals while keeping calorie intake low. This might include lean proteins, fruits, vegetables, and healthy fats.