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Before you start your IF plan, it's important to talk with a professional to make sure it's right for you. Women should be especially cautious as there are some mixed opinions on whether or not certain fasting protocols are healthy for female hormone balance. In addition, if you have adrenal fatigue or gut health issues you'll want to proceed with caution. If you have a history of disordered eating, you'll probably want to avoid fasting altogether..

You’ll spike your blood sugar when you eat. If you’re fasting on a high-carb diet and you’ve powered through the cravings and lack of energy from low blood sugar, there’s a good chance you’ll eat a ton of carbs when you feast. You want to eat big meals when you fast to make sure you’re getting enough calories, but all those excess carbs in one go will spike your blood sugar in the opposite direction, from low to high.[14] High blood sugar causes fatigue and lack of focus. That raging hunger will also cause you to binge unnecessarily, and whatever carbs you don’t use will get stored as fat.
In practice, however, I would be concerned with eating enough. Based on my experience, teaching yourself to consistently eat more is one of the harder parts of intermittent fasting. You might be able to feast for a meal, but learning to do so every day of the week takes a little bit of planning, a lot of cooking, and consistent eating. The end result is that most people who try intermittent fasting end up losing some weight because the size of their meals remains similar even though a few meals are being cut out each week.
Fasting ramps up your stem cell production.[6] Stem cells are like biological playdough — your body turns them into any kind of cell it needs and uses them to replace old or damaged cells, keeping you younger on a cellular level. Stem cells are great for your skin, joints, old injuries, chronic pain, and more. You can try stem cell therapy…or you can just fast.
Fast for 16 hours of the day, and allow yourself a single eight-hour window for eating. This may be a good option for most beginners, because it represents the most subtle change from the standard three-meals-per-day lifestyle. As approximately eight of those fasting hours should be spent getting a good night’s sleep, that leaves only eight hours where participants need to be consciously avoiding food. For many, allowing themselves to eat normally from noon until 8pm gives them a stable meal schedule while also staying in a fasted state for the majority of the time.
How It Works: This one’s easy: Eat very little one day, and eat like normal the next. On the low-calorie days, that means one fifth of your normal calorie intake. Using 2,000 or 2,500 calories (for women and men, respectively) as a guide, “fasting” (or “down”) day should be 400 to 500 calories. Followers can use this tool to figure out how many calories to consume on “low-calorie” days.
I’ll share some of my experiences, now doing heavy strength training for 3 years in a fasted state: For my first “fasted” workout or two after starting an IF protocol, it was very weird to not eat before training. However, after a few sessions, I learned that my body could certainly function (and even thrive) during my training sessions despite not eating a pre-workout meal.

Black coffee won't break your fast or take you out of ketosis. In fact, according to a report published in the Journal of Basic and Clinical Physiology and Pharmacology in 2017, caffeine may even increase your metabolism, which will help promote weight loss. Black coffee also helps curb your appetite, which can make getting through your morning fast much more manageable.

Third, you've probably already fasted many times, even though you don't know it. Have you ever slept in late on the weekends and then had a late brunch? Some people do this every weekend. In situations like these, we often eat dinner the night before and then don't eat until 11am or noon or even later. There's your 16–hour fast and you didn't even think about it.
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.
Forms of intermittent fasting exist in religious practices in various groups across the world.[12] Religious fasting regimens include, but are not limited to, Vrata in Hinduism, Ramadan fasting (Islam), Yom Kippur fasting (Judaism), Orthodox Christian fasting, Fast Sunday (The Church of Jesus Christ of Latter-day Saints), and Buddhist fasting.[12] Certain religious fasting practices, like Buddhist fasting, only require abstinence from certain foods, while others, like the Jewish fast on Yom Kippur, last for a short period of time and would cause negligible effects on the body.[12]
In animal studies, after two weeks of intermittent fasting, female rats stopped having menstrual cycles and their ovaries shrunk while experiencing more insomnia than their male counterparts (though the male rats did experience lower testosterone production). (6) Unfortunately, there are very few human studies looking at the differences between intermittent fasting for men and women, but the animal studies confirm our suspicion: Intermittent fasting for long periods of time can sometimes throw off a woman’s hormonal balance, cause fertility problems and exacerbate eating disorders like anorexia, bulimia and binge eating disorder.
In so far as insulin promotes de novo lipogenesis and suppresses lipolysis in adipocytes it DOES help keep the fat inside. But in Hyperinsulinemia / Insulin Resistance with Impaired Glucose Tolerance lipolysis may not be sufficiently reduced and fatty acids and glycerin can be spilled at the same time that Triglycerides are being formed & stored. In the liver the glycerin gets converted to glucose producing hyperglycemia.
Before the Nobel Prize was awarded to Yoshinori Ohsumi, other researchers were making groundbreaking discoveries about autophagy. In 2009, an article was published in Cell Metabolism entitled Autophagy Is Required to Maintain Muscle Mass. In this article, researchers described how deactivating an important autophagy gene resulted in a profound loss in muscle mass and strength.
Intermittent fasting may work amazingly well for some people, and terribly for others. Most importantly, if you do decide to give intermittent fasting a try, be sure to listen to your body’s feedback. Easing into intermittent fasting by starting with shorter fasting windows can help with initial symptoms of hunger and discomfort. But if it becomes too uncomfortable, be honest with yourself, accept it, and move on.
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.
Finally, note that fasting to induce ketosis can also trigger a set of symptoms often known as the “keto flu.” Fasting ketosis symptoms may include decreased energy levels, increased cravings, digestive issues, muscle aches and dizziness. These symptoms can last between a few days to a few weeks when starting the ketogenic diet, but they typically subside once your body enters ketosis and begins to adapt.
Fill your plate with plenty of healthy fats, such as coconut oil, avocados, olive oil, ghee and grass-fed butter as well as moderate amounts of protein foods like grass-fed meat, free-range poultry, fatty fish and eggs. Non-starchy vegetables, fresh herbs, nuts, seeds and healthy beverages like water, bone broth and green tea can all be enjoyed as well.
That window can be shrunk or expanded depending on your needs and preferences but typically, it’s somewhere between 4-7 hours of feeding during the day. Intermittent fasting is a great practice for weight loss, appetite control, digestion, and health on its own. When it’s combined with the keto diet and its benefits, the results can be even better.

Diluting a small amount of apple cider vinegar in 8 ounces of water won't break your fast. In fact, it might actually be a really good idea. According to a study published in the Journal of Medicinal Food in 2018, apple cider vinegar can lead to positive metabolic changes that help promote weight loss. Drinking apple cider vinegar every day may also reduce total cholesterol, triglycerides and LDL or "bad cholesterol" levels.


To start, recognize that the bulk of your weight-loss is going to come from fasting, not from working out. Exercise will have other benefits, of course, like building and preserving muscle tissue, improving performance, and increasing endurance, but it won’t be where you’re really taking off the pounds. With this in mind, if your priority is to lose weight, you’ll need to be prioritizing meal planning over working out. As you start intermittent fasting, you may need to pull back from regular strenuous exercise, at least until you feel like your body is used to your new schedule.
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]

Diet soda doesn't contain any sugar, calories or carbohydrates, so it may seem like it's OK for fasting, but it's not that simple. Diet soda and other diet drinks are filled with artificial sweeteners, which can drastically increase sugar cravings, making fasting more challenging. Artificial sweeteners can also increase insulin resistance, which makes it harder to lose weight and increase your risk of developing diabetes.

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.
In fact, the authors of this book said that they had patients who only changed their eating habits with this twelve- to sixteen-hour “fruit” fast each day. They did not follow the diet’s other rules or count calories, and they still lost weight and got healthier. This strategy might have simply worked because the dieters replaced junk food with whole foods. In any case, people found this dietary change effective and easy to make. Traditionalists won’t call this fasting; however, it’s important to know that you may have options if you absolutely can’t abstain from food for several hours at a time.

Worried about losing muscle if you fast? Maybe this will put your concerns to rest: a single 24-hour fast increased human growth hormone (HGH) by 2000% in men and 1300% in women.[2]  HGH plays an integral role in building muscle. Boosting your levels this high will have huge effect on your physique. Research shows that higher levels of HGH leads to lower levels of body fat, higher lean body mass and improved bone mass.[3]
For this reason, certain experts believe that intermittent fasting improves a broad range of neuro-degenerative conditions, including stroke, Huntington’s disease, Parkinson’s disease, and Alzheimer’s disease. After conducting a study on animals, researchers at the National Institute on Aging, found that cyclical fasting helps neurons in the brain to resist degeneration and dysfunction.
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.
I don’t recommend that you go straight for a 1-2 day fast, but begin by restricting yourself to certain eating windows. Typically people restrict themselves to the hours of 5pm – 11pm. People often refer to their fasting windows by numbers: 19/5 or 21/3, for example, means 19 hours of fasting and 5 hours eating or 21 hours fasting and 3 hours eating, respectively.
You’re consuming less food and thus spending less money. Rather than overeating to put on 1 pound of muscle and 4 pounds of fat in a week or two, you’re aiming to eat exactly enough to put on 1 pound of muscle without adding much fat on top of it.  Yeah, it’s a delicate balance, but there’s far less swing involved. You are just slowly, steadily, and consistently building muscle and strength over many months.
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