I have been following a 16/8 IF protocol for about 2 month now. I'm calling it 16/8, but sometimes stretch it to 17/7 or even 18/6. While I do not mean this in a negative way, I have not seen any benefits from it. I was at my goal weight when I started, but still have some belly fat, and feel like I could afford to lose another 10 lbs. I have seen normal fluctuation of a couple lbs either way over the 2 months, but no real change. To be fair, this is not scientific, as I have also made some other changes in that period. For example, I stopped recording every detail of what I eat, but still stick to a low carb diet. I stopped tracking weather I was in ketosis, but I was not in ketosis for most of my weight loss. I added some basic exercise, push ups, burpees, lung, but nothing high intensity. While not weighing and recording calories, I know they are lower, as the 10am to 6pm feeding window keeps me from snacking in the evening, and eliminates the need for between meal snacks.
IF is supposed to have a lot of benefits, such as insulin sensitivity, autophagy, increased hgh, etc. I have no reason to doubt that, but I have no realistic way to measure or know how those effect me.
Leangaines or 16/8 seems to be a popular IF protocol, but most of the studies I have looked at use alternate day fasting. The study referenced in the original post states they developed a 2 day eating with 1 day fasting protocol because to lessen the difference in caloric intake between the test subjects. That doesn't seem to be how most people IF, and it is not clear to me how much the time frame or protocol affects the results.
There is a wide range of opinion on what is allowed during the fast. For example, I recently saw an interview where it was stated anything but water will cause the body to expect food, and make changes that affect the fast. I have seen other opinions, Dr. Jason Fung for example, who say cream in coffee and bone broth is Ok. Others say you can have certain fats during the fast. I have not seen any research that tests how these differing approaches actually affect the benefits like autophagy and hgh. Rather these all seem to be just opinion.
Even with these uncertainties, I do plan to continue to follow the IF or time restricted eating protocol for the near future. If nothing else, I like that it has helped me to stop the evening snacks. I have found that to stay in ketosis, I need to pretty much be on Atkins 72 induction, which he called biologically zero carbs. I may try that again with the IF, and see how that goes for the next 2 months. In the meantime, I am interested in how other people see or consider these IF uncertainties.