This is the same as the 8-to-6 window plan, but you are extending your fasting time an extra four hours. I personally practice this plan during the workweek. I'm not a breakfast person, so I just enjoy a few cups of herbal tea to start my day. With this plan you will be eating only between the hours of 12 p.m. and 6 p.m. for a full 18 hours of fasting within a 24-hour period.
Because of the massive amount of sugar that Americans eat on average, most people have become dependent on glucose, instead of fatty acids, for energy. Every supermarket, grocery store and coffee shop sells an abundance of sugary foods and drinks. When you eat a lot of sugar, and that sugar isn't utilized for energy, your body breaks it down and eventually stores it as body fat.
Fat loss. Keto and intermittent fasting are a one-two punch for losing weight. Fasting and keto both spontaneously increase fat loss, even when people don’t intentionally restrict their calories.[18][19] When you pair intermittent fasting and keto together, you become a fat-burning machine. The weight comes off quickly, and because keto also suppresses ghrelin, you don’t get nearly as much of the hunger and feelings of deprivation that usually accompany weight loss.

Zero-calorie beverages are okay.  I drink green tea in the morning for my caffeine kick while writing. If you want to drink water, black coffee, or tea during your fasted period, that’s okay.  Remember, don’t overthink it – keep things simple! Dr. Rhonda Patrick over at FoundMyFitness believes that a fast should stop at the first consumption of anything other than water, so experiment yourself and see how your body responds.

Alternate-day fasting. Go back and forth between feasting days and fasting days. Eat like a king or queen one day, then eat nothing the next. This will probably be the most challenging fasting option for most people. If you try it, make sure you’re eating a ton on your feast days, otherwise you’ll fall into a major calorie deficit and you’ll likely feel miserable.
This is excellent, thank you! One thing I would love to see added to this research is the keto effect of just water over those 120 minutes, and THEN the keto effect of adding a tad bit of protein, such as collagen powder (I use the green tub great lakes powder; it dissolves great in coffee). I feel like that might put your test even more into an annals of science, and for us folks who don’t have the finger prick blood testers, it would be fun to know. Also, sugar free sweeteners like splenda (!!) or stevia–do they have any effect? Anyway–great read, exactly what I was looking for when I googled my question.
As a functional medicine practitioner, I see a wide range of health problems that all stem from chronic inflammation. And while acute inflammation is a natural and healthy response to help fight off pathogenic bacteria and infections, long-term chronic inflammation that doesn’t subside when the threat is gone can contribute to everything from autoimmune conditions to cancer.
On this plan you'll eat clean five days of the week but will not eat anything for two nonconsecutive days of the week. For example, you can fast on Monday and Thursday but eat clean meals on the other days. Food on these five days will look just like the rest of the fasting plans—healthy fats, clean meat sources, vegetables, and some fruit. Keep in mind that this plan is not for beginners, and you should always talk to your doctor before starting any fasting regimen, especially if you are on medication or have a medical condition.
While the idea of fasting can be overwhelming, especially if you haven’t done it before, intermittent fasting can actually be a lot easier than many other types of eating plans. Since you are fasting for time restricted chunks of the day, you’ll be eating less food, which eliminates a lot of the stress around having to meal prep. During the periods of time in which you're eating, you’ll still want to focus mainly on healthy fats, clean protein, and carbohydrates from whole food sources—but this isn’t an excuse to hit the drive-thru and load up on sugar the rest of the time! Here are some of the effects of intermittent fasting:
The five most common methods of intermittent fasting try to take advantage of each of these benefits. But different methods will yield better results for different people. “If you’re going to force yourself to follow a certain method, it’s not going to work,” says trainer and fitness expert Nia Shanks. “Choose a method that makes your life easier,” she says. Otherwise, it’s not sustainable and the benefits of your fasting may be short-lived.
On the flip side of that, eating keto can make your periods of fasting more manageable. For example, someone who is eating a diet higher in carbs will likely have more discomfort with intermittent fasting as the body constantly switches between glucose for fuel and ketones for fuel. By continuing to eat keto even during feeding periods, you can keep your body constantly running on ketones.
When you eat a meal, your body spends a few hours processing that food, burning what it can from what you just consumed.  Because it has all of this readily-available, easy to burn energy (thanks to the food you ate), your body will choose to use that as energy rather than the fat you have stored.  This is especially true if you just consumed carbohydrates/sugar, as your body prefers to burn sugar as energy before any other source.