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.
For example, in the graphic below you would eat dinner on Monday night and then not eat again until Tuesday evening. On Wednesday, however, you would eat all day and then start the 24–hour fasting cycle again after dinner on Wednesday evening. This allows you to get long fast periods on a consistent basis while also eating at least one meal every day of the week.
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16-hour fast (aka 16:8): The most popular type of intermittent fast, the 16-hour fast encourages you to eat all of your meals in an 8-hour window, such as noon to 8pm. To activate the full benefits of intermittent fasting, try an 18-hour fast, once you’ve adapted to 16 hours. This would mean eating between noon and 6pm or between 2pm and 8pm. Simply avoid eating after dinner, and skip breakfast in the morning. Limit carbs to dinner.
None of the coffee additives caused a significant drop in our blood ketone levels. At 120 minutes, my, (Becky’s), ketone readings increased after drinking black coffee, coffee with cream, coffee with MCT oil, and coffee with butter. At 120 minutes, Keith’s ketone readings dropped by 0.1 mmol/L after drinking only black coffee. His ketone readings rose slightly after consuming coffee with cream, MCT oil, and butter.
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Keep these studies in mind as your body tries to play tricks on you during your first day of fasting.  Even after three days of fasting, health complications are highly unlikely. However, it is important to know about the possible issues that can be caused by fasting. If you choose to incorporate fasting into your daily diet, you typically want to eat every day as well. Occasionally going on a longer period of fasting.
And while this may sound difficult, it’s really not. After all, the reasons our bodies store fat in the first place is because we, as a species, aren't really designed for constant eating. The three-square-meals (or more) eating plan is a relatively new phenomenon in human history; for much of our past, feast and famine were the order of the day. Our bodies know how to handle long stretches without food, and they know how to make good use of the “feasts” when they come along.

What if we told you that the answer to losing weight, improving body composition, and feeling better isn’t about dieting, but instead skipping meals every once in a while? For some, intermittent fasting, or going a longer period of time — usually between 14 and 36 hours — with few to no calories, can be a lot easier than you may think. And the benefits might be worth it. If you think about it, all of us “fast” every single day — we just call it sleeping. Intermittent fasting just means extending that fasting period, and being a bit more conscious of your eating schedule overall. But is it right for you? And which method is best?


Autophagy is spring cleaning for your cells. It’s Latin for “self-eating,” which is spot-on: when autophagy turns on, your cells sift through their internal parts, get rid of anything that’s damaged or old, and install shiny new versions.[8] Autophagy is like a tune-up for your car: afterward everything runs more smoothly. It reduces inflammation and even boosts longevity. Intermittent fasting triggers, to quote researchers, “profound” autophagy, especially in your brain.[9]


There are many different variations of intermittent fasting as well. Dr. Dom D’Agostino, the well-known ketogenic diet researcher, suggests doing a longer intermittent fast for 3 days, 3 times a year. This means not eating for 3 days, and eating normally until the next fast. Daily intermittent fasts are recommended as well. He says that it is ideal to have one to two meals after fasting for most of the day to reap the benefits of intermittent fasting every day.
When our cells undergo the process of autophagy, non-essential parts like damaged proteins are recycled and invading microorganisms and toxic compounds are removed. This means that autophagy plays an important role in stopping the aging process, reversing disease, and preventing cancer, but it doesn’t happen all the time. Fasting, protein restriction, and carbohydrate restriction are the three main ways that can initiate different autophagic processes — all of which are not the same. This is part of the reason why a ketogenic diet has so many positive effects, and it also shows you why intermittent fasting is a way to improve your diet even more.
You’ll run out of energy. When you don’t have anything in your system for several hours, your blood sugar will eventually drop below baseline. If you’ve ever had a blood sugar crash, you know how this state feels. Sleepiness, trouble focusing, lightheadedness, intense cravings, and the occasional mood swing typically accompany low blood sugar. Your cells run low on fuel and they start demanding that you give them more carbs.[13]
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While it’s not technically fasting, some doctors have reported intermittent fasting benefits by allowing such easy-to-digest food as whole fruit during the fasting window. Modifications like these can still give your digestive and metabolic system a needed rest. For example, “Fit for Life” was a popular weight loss book that suggested eating only fruit after supper and before lunch.
After determining your preferred protocol of intermittent fasting, you should start planning out your diet for the days that you do eat. On a standard keto diet, 75 percent of total calories should come from fat, 20 percent should be from protein and 5 percent should come from carbs. When getting started, however, you can start with a modified keto diet instead, which is often considered more flexible and easy-to-follow. With this diet plan, about 40–60 percent of calories should come from healthy keto fats with 20–30 percent from protein foods and 15–25 percent from carbohydrates.
I have since reviewed another new and amazing intermittent program called Science Based Six Pack, you can read my full in-depth review of this program here, Science Based Six Pack Review. I have also purchased this program as well, and it is very thorough and detailed, as well as very user-friendly. This is my new number #1 recommended program for a highly effective intermittent fasting program.
So how long does it take to go into ketosis when fasting? On a standard keto diet, it typically takes around 2–3 days to reach ketosis, although it can take up to seven days in some cases. However, many people find that keto adaptation intermittent fasting can speed up the process and help your body burn through glycogen stores more quickly to help enter ketosis.

Intermittent fasting is a technique that involves restricting your food intake to a certain time window each day and then fasting for a specific period. There are several different fasting methods, with many variations that can fit nearly any personal preference or routine. A few of the most common types of intermittent fasting include alternate day fasting, 16/8 fasting and the 5:2 diet, each of which varies based on the amount of time you spend fasting during the week.

I was very curious about this, so I asked the opinion of metabolic expert Dr. Deborah Wexler, Director of the Massachusetts General Hospital Diabetes Center and associate professor at Harvard Medical School. Here is what she told me. “There is evidence to suggest that the circadian rhythm fasting approach, where meals are restricted to an eight to 10-hour period of the daytime, is effective,” she confirmed, though generally she recommends that people “use an eating approach that works for them and is sustainable to them.”
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The four-hour eating window — which Hofmekler refers to as the “overeating” phase — is at night in order to maximize the Parasympathetic Nervous System’s ability to help the body recuperate, promoting calm, relaxation and digestion, while also allowing the body to use the nutrients consumed for repair and growth. Eating at night may also help the body produce hormones and burn fat during the day, according to Hofmekler. During these four hours, the order in which you eat specific food groups matters, too. Hofmelker says to start with veggies, protein and fat. After finishing those groups, only if you are still hungry should you tack on some carbohydrates.
Pros: According to the founders, while everyone is technically fasting every day — during the hours when we’re not eating — most of us do so haphazardly, which makes it harder to reap the rewards. Fat Loss Forever offers a seven-day schedule for fasting so that the body can get used to this structured timetable and reap the most benefit from the fasting periods. (Plus, you get a full cheat day. And who doesn’t love that?)
How It Works: Fast for 14 (women) to 16 (men) hours each day, and then “feed” for the remaining eight to 10 hours. During the fasting period, you consume no calories. However, black coffee, calorie-free sweeteners, diet soda and sugar-free gum are permitted. (A splash of milk in your coffee won’t hurt, either.) Most practitioners will find it easiest to fast through the night and into the morning. They usually break the fast roughly six hours after waking up. This schedule is adaptable to any person’s lifestyle, but maintaining a consistent feeding window time is important. Otherwise, hormones in the body can get thrown out of whack and make sticking to the program harder, Berkhan says.
The problem is that we tend to spend so much time in the fed state, fueling our bodies exclusively with glucose, that we become addicted. Once the flow of glucose stops and our insulin levels drop, we start getting hunger pains. This is one of the reasons that overweight individuals — people with more than adequate energy stores in their fat cells — often have such a difficult time cutting back on food intake. They’re not starving, but they’re not getting the glucose their bodies are used to.
Some people believe that IF has worked for them simply because the limited eating window naturally helps them reduce the amount of calories they consume. For instance, instead of eating three meals and two snacks, they might find that they only have time for two meals and one snack. They become more mindful about the kinds of food they consume and tend to stay way from processed carbs, unhealthy fat, and empty calories.
Intermittent fasting (intermittent energy restriction or intermittent calorie restriction) is an umbrella term for various eating diet plans that cycle between a period of fasting and non-fasting over a defined period. Intermittent fasting is under preliminary research to assess if it can produce weight loss comparable to long-term calorie restriction.[1][2][3][4][5]
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For example, in the graphic below you would eat dinner on Monday night and then not eat again until Tuesday evening. On Wednesday, however, you would eat all day and then start the 24–hour fasting cycle again after dinner on Wednesday evening. This allows you to get long fast periods on a consistent basis while also eating at least one meal every day of the week.
IF makes intuitive sense. The food we eat is broken down by enzymes in our gut and eventually ends up as molecules in our bloodstream. Carbohydrates, particularly sugars and refined grains (think white flours and rice), are quickly broken down into sugar, which our cells use for energy. If our cells don’t use it all, we store it in our fat cells as, well, fat. But sugar can only enter our cells with insulin, a hormone made in the pancreas. Insulin brings sugar into the fat cells and keeps it there.
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