Dr. Jason Fung: Fasting as a Therapeutic Option for Weight Loss

you should check out this talk to understand why that's the case and it might be different with fasting this video

I don't recommend anything more than 3-5 days max. Without knowing what your goal is just try the 16:8 and eat a nutrient rich diet that is low energy. You should be able to fit 2 meals in (lunch and dinner) in a window from 12 - 8 pm. Nothing but water/coffee/tea before or after that window. If your healthy and don't suffer from any issues, move on to one meal a day. After you master that then try a 1 or 2 day fast. Look up Jason Fung on youtube. Great stuff.... this video Check out Dr Berg on youtube also. He does "Healthy Keto" which is a very balanced and healthy diet. link Lots of great resources out there....

You need to wait 12-24 months before you can consider your diet a success. A caloric deficit doesn't work long term, as over time your metabolism slows down to match the caloric intake. "The key to long-lasting weight control is to control the main hormone responsible, which is insulin. Controlling insulin requires a change in our diet, which is composed of two factors — how high the insulin levels are after meals, and how long they persist. This boils down to two simple factors: What we eat — which determines how high insulin spikes; and When we eat — which determines how persistent insulin is." The best resource for weight loss via fasting is Dr. Jason Fung this video link (link looks a bit spammy, but contains good information)