What's the worst type of fasting?

Alternate day fasting is when you would fast for one day, and then the next day, you would eat whatever you want. This is an ineffective method of fasting because it is inconsistent, so it makes it difficult for your body to reap the benefits of fasting. Another ineffective method of fasting is the 5:2 method,

With the 5:2 fasting pattern, you can eat whatever you want for five days, and then you fast for two days. This is a poor fasting method because it is essentially just calorie restricting two days a week, and will not actually benefit you in the many ways a 16:8 or 20:4 fasting pattern will.