How Alternate-Day Fasting Can Help You Achieve Your Weight Loss Goals

You don't have to diet every day to lose weight. This compelling concept is the focus of Dr. Krista Varady's book The Every-Other-Day Diet: The Diet That Lets You Eat All You Want (Half the Time) and Keep the Weight Off.
Dr. Varady is an associate professor of nutrition at the University of Illinois in Chicago, and in this interview, she reveals how intermittent fasting can help you achieve optimal health and weight without starving yourself every day. She explains what prompted her to investigate, and eventually write a book on this topic.
"I wanted to do a PhD in the area of calorie restriction and fasting," she says. "I wanted to find out: do you really have to diet every single day to lose weight? I noticed that people just weren't able to stick to calorie restriction programs for more than about a month or two. Everyone dropped off of their diet.
I thought: 'is there a way to manipulate that eating pattern that will allow people to stick to it longer? Maybe you could diet every other day?' That way you can always look forward to the next day, where you can eat whatever you want. Maybe that would help people kind of stick to these diets?"
As it turns out, her hunch was correct. Alternate-day fasting has a far greater retention- and compliance rate compared to conventional all-day fasting regimens. My preferred version of intermittent fasting, which simply calls for restricting your eating to a narrower window of about six to eight hours or so each day, also has a far greater success rate than more extensive fasting protocols.

Complete versus Intermittent Fasting

Complete fasting is when you consume nothing but water for 24 hours, midnight to midnight, at regularly recurring intervals. This kind of calorie restriction has well-documented health benefits, including life extension, but the compliance rate for this kind of program is low. It's just too severe for the vast majority of people.
Intermittent fasting is an umbrella term that covers a wide array of fasting schedules, including the 5:2 approach. As a general rule however, intermittent fasting involves cutting calories in whole or in part, either a couple of days a week, every other day, or even daily, as in the case of the scheduled eating regimen I use myself.
Dr. Varady's research shows that alternate-day fasting, where you consume about 500 calories on fasting days and can eat whatever you want on non-fasting days, works equally well for weight loss as complete fasting, and it's a lot easier to maintain this type of modified fasting regimen.
In her study, which was recently completed, participants ate their low-calorie fasting day meal either for lunch or dinner. Splitting the 500 calorie meal up into multiple smaller meals throughout the day was not as successful as eating just one meal, once a day.
The main problem relates to compliance. If you're truly eating just 500 calories in a day, you will lose weight. But when eating tiny amounts of food multiple times a day, you're far more inclined to want more, so the cheat rate dramatically increases.

What About Alternate-Day Fasting?

Alternate-day fasting is very much in alignment with Paleo perspectives that seek to replicate the behaviors of our ancient ancestors to optimize health. In our ancient past, people did not have access to food around the clock. They would cycle through periods of feast and famine, which modern research shows actually has biochemical benefits.
The reason so many struggle with their weight (aside from eating processed foods that have been grossly altered from their natural state) is because they're in continuous feast mode and rarely ever go without a meal. As a result, their bodies have adapted to burning sugar as its primary fuel, which down regulates the enzymes that utilize and burn stored fat. Fasting is an excellent way to "reboot" your metabolism so your body can start burning fat as its primary fuel, which will help you shed your unwanted fat stores.
"It takes about a week to 10 days or so to get used to that up-down pattern of eating," she says. "But it's amazing. Even though people struggle through the first week, they always say, 'After a week, I had no problem eating just 500 calories every other day.'"

Tips for Making It Through the Transition Period

The toughest part, of course, is getting through that initial transition, which can be anywhere from seven to 10 days. Maybe even longer for some people, depending on how insulin-resistant you are, and other factors, like your weight, blood pressure, and cholesterol levels, and if you are not consistent with the fasting and wind up cheating.
About 10 percent of people will report headaches as a side effect when they first start fasting, but the biggest complaint is feeling hungry. It may be helpful to remember that part of why you're craving food is because your body has not yet fully switched from burning sugar to burning fat as its primary fuel. Sugar is a fast-burning fuel, whereas fat is more satisfying. As long as your body is using sugar for fuel, it will "remind" you that it's running low and needs a refill at regular intervals. So part of the challenge is getting through that transition period. Another factor is purely psychological. As Dr. Varady explains:
"Many people are just used to eating constantly. Not only is it actual hormonal responses, but I think it's just habit... Most people eat just because they're bored. I think a lot of it is psychological—that's what takes people a while to get used to. In terms of helping people get through that, we always recommend drinking a lot of water (eight to 10 extra glasses of water a day). Because people will often think that they're hungry, but really they're thirsty...
We also tell people to watch less television. You don't realize how bombarded you are with food commercials; something like 60 percent of commercials are about food. That's why most people will end up getting a snack within half an hour when they're sitting down and watching TV."

The vast majority of Americans are overweight and most would therefore benefit from this type of eating regimen (adrenal-fatigued individuals are perhaps an exception to this rule). When done correctly, you will inevitably lose weight and your insulin and leptin receptor sensitivity will be optimized, which is really important for optimal health. The next question then becomes, do you have to continue on indefinitely with this alternate-day fasting schedule?

How Long Must You Remain on an Alternate-Day Fasting Schedule?

Dr. Varady is currently investigating this question through a study funded by the National Institutes of Health (NIH). The study is set up to be a year long, with six months of weight loss through alternate-day fasting, followed by six months of weight maintenance. She'll compare the results against a traditional approach of calorie restriction and traditional weight maintenance where you eat just 100 percent of your energy needs every day.
"We're almost done with the study," she says. "What we're noticing now is that people can use every-other-day dieting for weight maintenance. However, you need to tweak it a little bit in that you reduce the fasting days down to three days per week, and instead of consuming 500 calories on each of those days you'd consume 1,000... In terms of comparing it to daily calorie restriction, it actually does a little bit better. People in the every-other-day dieting group were actually able to maintain their weight a little bit better than people doing a traditional maintenance approach. "
So, it appears you do have a bit more flexibility once you've reached your weight loss goal. In terms of what to eat, Dr. Varady's book ultimately advocates transitioning into a Mediterranean-type diet.
"We do want people to slowly change their eating habits. But we find that if we kind of overwhelm people with not only the 'eat 500 calories every other day' but then tell them to change all their dietary patterns right away, people quit the diet and tend to do nothing," she says. "It's good if you can just start the actual up-down approach of eating, just the 500 calories every other day, and then slowly transition into whole foods and basically healthier foods."
So in summary, you don't have to keep on intermittently fasting forever if this is a lifestyle strategy that doesn't appeal to you long-term. If you need to lose 50 pounds, you're looking at about six months or so of intermittent fasting, after which you can revert back to eating more regularly. I strongly recommend paying careful attention to your food choices, however. Even on non-fasting days, I believe it's important to eat a diet that is:
  • High in healthy fats. Many will benefit from 50-85 percent of their daily calories in the form of healthy fat from avocados, organic grass-fed butter, pastured egg yolks, coconut oil, and raw nuts such as macadamia, pecans, and pine nuts
  • Moderate amounts of high-quality protein from organically raised, grass-fed or pastured animals. Most will likely not need more than 40 to 80 grams of protein per day.
  • Unrestricted amounts of fresh vegetables, ideally organic

Exercise Is an Important Part of the Weight-Loss Equation

The next question is whether or not it might be beneficial to exercise on fasting days. Will you have enough energy to exercise, and if so, what type of exercise is recommended?
"The main study that we ran on this was to see if you combined every-other-day dieting with exercise, when should you time the exercise session? And do people even want to do that?" Dr. Varady says. "We found out that, yes, you can exercise on the fast day. In general, it's better if you exercise before the fast-day meal. Because what happens is that about an hour or so after you exercise, a lot of people experience a hunger surge. If you have that fasting meal right after you exercise session, you get to eat the meal and you're happy."
Those who exercised after their fast-day meal oftentimes ended up cheating, and surpassing their 500-calorie goal for the day. So ideally, exercise before your scheduled meal for the day. In terms of the types of exercise that might be recommended, Dr. Varady has only studied endurance training. However, as I've discussed on many occasions, conventional endurance exercises like running are really among the least effective types of exercise for weight loss. From my perspective, you'd be far better off opting for some form of high intensity interval training, even on your fasting days, as this will really boost your body's ability to burn fat.
Previous research has also shown that high intensity interval training produces significant improvements in many of your hormone distributions, including brain-derived neurotrophic factor (BDNF) and human growth hormone (HGH). It's also far more time efficient. Instead of 45 minutes to an hour on the treadmill, you can be done in 20 minutes. And you don't do it every day. You only do it two or maybe three times a week. No more than three because the recovery component is an important part of the program. I also recommend incorporating other types of exercise, such as strength training, core exercises,
and stretching.

Who Should Use Extra Caution When Fasting, or Avoid It Altogether?

Intermittent fasting is appropriate for most people, but if you're hypoglycemic or diabetic, you need to be extra cautious. People that would be best served to avoid fasting include those living with chronic stress (adrenal fatigue), and those with cortisol dysregulation. Pregnant or nursing mothers should also avoid fasting. Your baby needs plenty of nutrients, during and after birth, and there's no research supporting fasting during this important time.
My recommendation would be to really focus on improving your nutrition instead. A diet with plenty of raw organic foods and foods high in healthy fats, coupled with high-quality proteins, will give your baby a head start on good health. You'll also want to be sure to include plenty of cultured and fermented foods to optimize your—and consequently your baby's—gut flora.
Hypoglycemia is a condition characterized by an abnormally low level of blood sugar. It's commonly associated with diabetes, but you can be hypoglycemic even if you're not diabetic. Common symptoms of a hypoglycemic crash include headache, weakness, tremors, irritability, and hunger. As your blood glucose levels continue to plummet, more severe symptoms can set in, such as:
  • Confusion and/or abnormal behavior
  • Visual disturbances, such as double vision and blurred vision
  • Seizures
  • Loss of consciousness
One of the keys to eliminating hypoglycemia is to eliminate sugars, especially fructose from your diet. It will also be helpful to eliminate grains, and replace them with higher amounts of quality proteins and healthy fats. You can use coconut oil to solve some of these issues as it is a rapidly metabolized fat that can substitute for sugar, and since it does not require insulin, it can be used during your fast. However, it will take some time for your blood sugar to normalize. You'll want to pay careful attention to hypoglycemic signs and symptoms, and if you suspect that you're crashing, make sure to eat something, like coconut oil. Ideally, you should avoid fasting if you're hypoglycemic, and work on your overall diet to normalize your blood sugar levels first. Then try out one of the less rigid versions of fasting.

Alternate-Day Fasting: Key Points to Remember

Again, the alternate-day fasting regimen Dr. Varady promotes involves fasting every other day. On fasting days, you limit your food intake to 500 calories; ideally consumed in one meal, either at lunch or dinner. Eating your one meal for breakfast tends to set you up for failure, as you'll then spend the rest of the day thinking about how you'll have nothing to eat until the following morning. From a psychological and compliance perspective, it's easier to go without if you know you can eat something in the middle or toward the end of the day.
On non-fasting days, you can eat whatever you want, without counting calories 
I still recommend cleaning up your diet and not indulging in too many processed foods.  Besides promoting greater compliance, mounting research also shows that skipping breakfast is actually better for your health. Most of the research supporting the notion that breakfast is the most important meal of the day is actually funded by cereal companies.
"I did a massive literature search and I found out that [skipping breakfast} is actually not that bad for you. You just have to look at who's funding the studies," Dr. Varaday notes. "Other things I definitely advocate with this diet, to make it easier, are drinking tons of fluids, particularly on your fast day. Try to consume protein on that day. It helps with satiety. It really depends on what your body size is but maybe 30 to 40 grams of protein.
I usually recommend a salad with some type of protein on it, like chicken. If you're vegetarian, use beans or that type of thing. The great thing is you don't have to count calories every other day. Every other day, you really get to kind of feel normal. A lot of people say that they actually have healthier cravings on the feast day. It's really interesting. The body's kind of like resetting itself."
I would add that you'll want to make sure you're getting plenty of healthy fat in your diet, both on fasting and non-fasting days. Good sources include the following.
AvocadosButter made from raw grass-fed organic milkRaw dairyOrganic pastured egg yolks
Coconuts and coconut oilUnheated organic nut oilsRaw nuts, such as almonds, pecans, macadamia, and seedsGrass-fed meats

Easier Way to Achieve Calorie Restriction Benefits

If you're looking for the proverbial fountain of youth, most researchers and scientists will likely agree that calorie restriction is about as close as you can come.
Research shows that you can slow down aging and significantly increase your lifespan simply by lowering your caloric intake. The effects have been observed in a variety of species from worms and yeast to rats and fish, and there's evidence that calorie restriction has a similar effect on the human lifespan, as well.
Despite its simplicity and proven merit, calorie restriction remains a strategy few people are willing to embrace, but what if you found out the beneficial effects happened rapidly, allowing you to potentially slow down and even reverse the aging process after just a few days or weeks?

Calorie Restriction Provides Anti-Aging Benefits, Fast

Calorie restriction is known to alter the expression of hundreds to thousands of genes, some of which are related to longevity and some of which play a role in metabolism, cell growth, reproduction, immune response, and more.

What is perhaps most exciting is the speed with which these beneficial changes occur. We're not talking about an effect that takes decades to occur, we're talking about benefits that begin virtually immediately. According to one recent paper in regard to calorie restriction in fruit flies, the beneficial changes occurred within days of restricting calories:

"…diet switches rapidly alter age-specific mortality… Remarkably, when flies are shifted from a rich diet to just a relatively restricted diet, within days the cohort adopts the same trajectory of low age-specific of adults continuously maintained on restricted diet (and vice versa for cohorts switched from restricted to rich diets).
…These observations suggest that the molecular, cellular and physiological changes caused by DR [dietary restriction] to extend lifespan must occur within a short time frame after adults experience an alternative diet."
Other animal studies have similarly found that the life-extension effects of calorie restriction not only happen rapidly but also occur among old animals that have never been on a calorie-restricted diet before.
What this implies for humans, of course, is that it may lead to rapid changes in genetic expression that promote longevity – even if you're new to calorie restriction. According to researcher Stephen Spindler, Ph.D
"I think the conclusion you can reach from the paper is that even in very old animals, caloric restriction will very rapidly produce most of the gene expression effects that you see in long-term calorie-restricted animals.
That means, I think, that even in the short-term, older people may be able to benefit rapidly from switching to a calorically-restricted diet, and that fits with some of the information that has been in the literature for years.
For instance, type II diabetics improve when they start under-eating. Their blood glucose levels improve. Their insulin sensitivity improves. Their general health improves, even before the fat mass, for instance, is depleted. So, there have been some hints that underfeeding could produce positive effects rather rapidly…"

Short-Term Calorie Restriction May Fight Cancer

In addition to offering anti-aging and longevity benefits, research suggests that strategically restricting your calories may also be an effective form of cancer prevention and treatment, again with results appearing in a matter of days or weeks.

Reducing Your Calories Benefits Your Gut Health Too

There is an emerging consensus that most disease originates in your digestive system, and this includes conditions that impact your brain, your heart, your weight, and your immune system, among others. There's also evidence that the microorganisms present in your gut can affect how well you age, and this ties in directly with the latest research on calorie restriction and longevity.

One important thing to remember about the microbes in your gut is that they are not static. They can change profoundly throughout your life, for better or for worse, and one of the biggest influences on this change is your diet.
Indeed, research has shown that life-long calorie restriction in mice "significantly changes the overall structure of the gut microbiota" in ways that promote longevity. 
So it appears that one reason why calorie restriction may lengthen lifespan is because it promotes positive changes to the microorganisms in your gut. However, even if you're not keen on the idea of sacrificing a significant number of your daily calories for the rest of your life, there's a way to get the benefits that this dietary strategy has to offer.

Intermittent Fasting May Work Even Better Than Calorie Restriction (And It's Easier to Stick With)

The primary problem with calorie restriction is the compliance or willingness of anyone to stick with this painful depriving strategy is extremely low. My guess is that less than 1% of people would be willing to do this. Besides it is needlessly painful and uncomfortable as newer strategies that replicate ancestral eating patterns are likely to provide the same benefits and result in naturally reduced desire to eat excess calories.

Krista Varady with the University of Illinois has been researching the impact of fasting on chronic diseases like cardiovascular disease, type 2 diabetes, and cancer. Her work also compares the effects of intermittent fasting with caloric restriction. Animal studies using alternate-day fasting have shown it lowers the risk of diabetes at rates comparable to caloric restriction.

Alternate-day fasting has also been shown to reduce cancer rates by reducing cell proliferation. So what exactly is intermittent fasting, and how is it different from calorie restriction?

Calorie restriction involves reducing your daily calories by a certain percentage at every meal. Unfortunately, hunger is a basic human drive that can't be easily suppressed, so anyone attempting to implement serious calorie restriction is virtually guaranteed to fail. Fortunately, you don't have to deprive yourself as virtually all of the benefits from calorie restriction can be achieved through properly applied intermittent fasting.

There are many different variations of intermittent fasting. If you are like 85 percent of the population and have insulin resistance, my personal recommendation is to fast every day by simply scheduling your eating into a narrower window of time each day. I find this method to be much easier than fasting for a full 24 hours or more, twice a week, as some people suggest.
In order to understand how you can fast daily while still eating every day, you need to understand some basic facts about your metabolism. It takes most people 8 to 12 hours for their body to burn the sugar stored in your body as glycogen. Now, most people never deplete their glycogen stores because they eat three or more meals a day. This teaches your body to burn sugar as your primary fuel and effectively shuts off your ability to use fat as a primary fuel.
Therefore, in order to work, the length of your fast must be at least eight hours. Still, this is a far cry from a 24-hour or longer fast (or chronic calorie restriction), which can be quite challenging. I believe that, for most people, simply restricting the window of time during which you eat your food each day is far easier. For example, you could restrict your eating to the hours of 11am and 7pm. Essentially, you're just not eating anything for three hours before bed, skipping breakfast and making lunch your first meal of the day instead. This equates to a daily fasting of 16 to 18 hours—more than twice the minimum required to deplete your glycogen stores and start shifting into fat-burning mode.

The Quality of Your Calories Matters When Applying Intermittent Fasting

Please keep in mind that a proper nutrition plan becomes even more important when you're fasting and/or cutting calories, so you really want to address your food choices before you try any form of fasting. You need to make the calories you do consume count. Simply relying on fast food and processed foods during your non-fasting hours will not give you the longevity benefits you're after. So when you do eat, make sure to minimize carbs like pasta, bread, and potatoes.
Instead, exchange them for healthy fats like butter, eggs, avocado, coconut oil, olive oil, and nuts—essentially the very fats the media and "experts" tell you to avoid. You may also want to restrict your protein a bit if you're typically a big meat eater. I strongly suggest eating only high-quality pastured protein, and limiting it to about one gram of protein per kilogram of lean body mass (about one-half gram of protein per pound of lean body weight) may be appropriate for most people. (Note: if your body fat mass is 20 percent, your lean mass is 80 percent of your total body weight.) These kinds of food choices, in combination with intermittent fasting, will help shift you from carb-burning to fat-burning mode.

Fasting - A Powerful Treatment Strategy for Diabetes

We have an epidemic of diabetes in the United States. An estimated 30.3 million Americans, nearly 1 in 10, have Type 2 diabetes. Another 84 million American adults — about 1 in 3 — are prediabetic, and most are unaware of this fact. Prediabetesis defined as an elevation in blood glucose over 100 milligrams per deciliter (mg/dl) but lower than 125 mg/dl, at which point it formally becomes Type 2 Diabetes. 

However, any fasting blood sugar regularly over 90 mg/dl really suggests insulin resistance, and seminal work by the late Dr. Joseph Kraft, author of “Diabetes Epidemic and You: Should Everyone Be Tested?” suggests that 80 percent — 8 out of 10 — Americans are in fact insulin resistant,which means they’re already on their way toward developing diabetes.

That's the bad news. The good news is Type 2 diabetes is curable, and the cure is less than free. It actually saves you loads of time and money. In his book, The Diabetes Code: Prevent and Reverse Type 2 Diabetes Naturally,” Dr. Jason Fung details how to address this exceptionally common problem. Fung is a nephrologist (kidney specialist) with a practice in Toronto.

Why Identifying Insulin Resistance Is so Important

There are two types of diabetes, Type 1, or insulin dependent diabetes, and Type 2 diabetes, which is lifestyle related. Type 2 diabetes accounts for 90 to 95 percent of all diabetes cases and is the topic of this particular discussion. Prevalence of Type 2 diabetes started to rise in the 1980s, at a time when obesity had yet to become a significant trend. However, as obesity became more prevalent, so did Type 2 diabetes.

“But the fundamental underlying problem of Type 2 diabetes, which is insulin resistance, is actually much more widespread than that,” Fung says. “And the innovative thing Kraft did was that he took a standard glucose tolerance test, and measured blood insulin levels instead of blood glucose. Because if you think about what's happening, when you ingest 75 grams of glucose [the amount administered prior to the test], your blood glucose may stay normal.
But, your body may be producing a huge amount of insulin to really shove that glucose into the cell. Because one of the functions of insulin is to move the glucose from the blood into the cell. Insulin resistance refers to the fact that blood glucose is simply not getting in there. So, if your body needs to produce two, three, four, five times the amount of normal insulin to get that glucose in there, you have a problem, which is not detectable if you just measure blood glucose.
Because, yes, you are shoving all that glucose into the cell, but it took you a huge amount of effort to do so. And by [using the] Kraft assay, which looks at how much the insulin goes up, you can detect [insulin resistance] at a much earlier stage. This is important because there are things we can do about reversing … insulin resistance, and the sooner we get to it, the sooner we can get on the path to wellness.”

Ultimately, diabetes is just one symptom. Insulin resistance, which results in mitochondrial dysfunction, is also at the heart of cancer, heart disease, Alzheimer's and other degenerative diseases, and it all starts because your body is unable to burn fat as a primary fuel. When your body relies primarily on sugar instead, more reactive oxygen species (ROS) are generated, which damage the mitochondria in your cells.

Why Fasting Resolves Insulin Resistance, the Cause of Diabetes

Fasting has been used for thousands of years to keep us well. Once you understand what insulin resistance actually is and what Type 2 diabetes is, then you'll understand why something so simple as abstaining from food for a period of time can be such a powerful intervention. Contrary to infectious diseases, you cannot treat metabolic disease with a pill, because metabolic diseases such as diabetes are predicated on lifestyle, primarily diet. As explained by Fung:

“You have to use metabolic treatments, which is why using fat for fuel is so important. It really gets to the point that you cannot follow this old paradigm [of drug treatment] because you're going to fail … Remember, the glucose goes into the cell, and insulin resistance is when the glucose doesn't go out of the cell. So, for years we’ve used this paradigm of lock and key.
That is, the cell is sort of gated off. Outside the cell there's blood, and when insulin comes around it turns the key, opens the gate and glucose goes in. So, if insulin is there, why is the glucose not going in? … You can measure the insulin and the insulin level is high. You can look at the insulin receptor, the gate is completely normal.
So, [conventional medicine] said something like, ‘Well, maybe there's something gumming up the mechanism. It's stuck in the lock so it doesn't open properly, therefore the glucose can't get into the cell. There's a huge problem with this sort of paradigm, because if that is happening, the cell has no glucose and should be starving.
You should be losing lots of weight; you’d have a very thin liver. All your fat should just melt away, because if you think about untreated Type 1 diabetes, where you don't have enough insulin, that's exactly what happens. The cell literally starves and everything just wastes away … But that's not what's happening here.
In Type 2 diabetes you see that people are generally obese, they have large abdomens … What's happening instead is that it's actually an overflow syndrome. The cell can't accept any more glucose because it's jam packed full of glucose already. That's the reason you have insulin resistance. Insulin is trying to move glucose into the cell but the cell is full … So, it's really an overflow mechanism …
That's also why your liver is full — it's a big fatty liver. The liver is busy trying to get rid of all this glucose by turning it into fat … Now, if Type 2 diabetes and insulin resistance are the same sort of thing, it's really about too much sugar. That's the bottom line.
And if you understand that the whole problem is too much sugar, then the solution is not to use more insulin to jam more glucose into an already full cell. The key is to get rid of it all. So, what you want to do is: 1) Don't put more sugar into your system, because you have too much sugar in already, and 2) Burn it off.”

Why Exercise Cannot Replace Fasting

To avoid adding sugar into your body it is important to adopt a cyclical low-carb, high-fat diet. Then, to burn off the sugar already in your system, intermittent fasting or time-restricted eating is a powerful tool. Exercise is not the solution for diabetes, and cannot replace fasting.
Remember, you can’t out-exercise your mouth. The reason for this is because you not only have insulin resistance in your muscles, but in all your tissues and organs, and to eliminate the excess glucose in your organs you need to temporarily “starve” the cells.
Clearly, you should exercise, but that will only burn the glycogen in your muscles. It’s not going to address your fatty liver. As noted by Fung, fasting “gets rid of all the sort of excess nutrients. That's why, historically, people called it a cleanse or a detox, because that's really what it is.”
In his practice, Fung has used fasting for many years and can attest to the dramatic turnarounds possible. “We have people coming in with the most severe diabetes; they’re taking hundreds of units of insulin a day, and within three to four weeks we have them off everything.” Oftentimes, a severe diabetic can revert back to being nondiabetic within as little as two months.

Taking Insulin Worsens Type 2 Diabetes

This is not to say it’s easy. Fasting can be difficult when you’re used to eating multiple times a day. But it’s a natural way that will allow your body to heal itself. Meanwhile, taking insulin for Type 2 diabetes is about the worst thing you can do. As explained by Fung:
“What happens when you give insulin is that insulin lets your body use all that glucose, and when there's too much glucose, it's just going to [turn it into] fat. So, all these patients gain weight. And they always come back and say, ‘Whoa doc, you've told me I need to lose weight, then you give me insulin and I've gained 20 pounds. How is that good?’
And the answer is that it's not. As you gain more weight your diabetes gets worse, which means you need to take more insulin, which means you're going to gain more weight. They can see themselves spiraling down the drain, and the doctors do nothing but give them more insulin. It doesn't even make any sense because the underlying issue is the hyperinsulinemia and insulin resistance. That is, if you look at Type 2 diabetes, insulin levels are very high.
So [why give] more insulin in a situation where you have too much insulin already? If you have hyperthyroidism, if you have too much thyroid hormone, you don't give more thyroid hormone. If you have an alcoholic, you don't give more alcohol. It's the exact wrong thing to do. In fact, if your levels of insulin are too high and that's your disease, you need to lower insulin. By giving insulin, you're actually making the fundamental problem much worse.”

How Fasting Benefits Your Mitochondria

Fasting is the most profoundly effective metabolic intervention I’m aware of. It's like getting a free stem cell transplant, and it massively upregulates autophagy and mitophagy. It also stimulates mitochondrial biosynthesis during the refeeding phase, which allows your body to naturally regenerate. For these reasons, fasting is not only beneficial for Type 2 diabetes and obesity but also for health in general, and likely even longevity.
There’s even evidence to suggest fasting can help prevent or even reverse dementia, as it helps your body clean out toxic debris. As noted by Fung, “It's fundamentally one of the keys of wellness.” By lowering insulin, you also increase other important hormones, including growth hormone (aka the fitness hormone), which is important for muscle development and general vitality.
Other ailments that can benefit from fasting include polycystic ovaries, polycystic kidneys and fast growing cancer cells. The reason for this is because when autophagy increases, your body starts breaking down old protein, including fast growing cells. Then, during the refeeding phase, growth hormone increases, boosting the rebuilding of new proteins and cells. In other words, it reactivates and speeds up your body’s natural renewal cycle.

Getting Started

Most people fear being hungry and avoid it like the plague. Here, intermittent fasting can make the process a lot easier. Before I tried my first five-day water fast, I increased my intermittent daily fasting to the point that I was fasting for 20 hours a day for a few months, but one month is likely sufficient.
At that point, going several days without food was easy, since my body had had gained metabolic flexibility and was able to burn fat as my primary fuel, Most people get really hungry by Day Three on a water fast, yet I had no hunger at all. Fung agrees, saying:
“That's a great point. If you are fueling yourself primarily with carbohydrates, then you can't use fat very well … So, when you transition from a predominantly carbohydrate diet to a predominantly fat-based diet, your body can't store glycogen, because those are chains of glucose, it needs to burn body fat (or dietary fat). To your body it's sort of the same thing, they're just triglycerides.
When you biopsy muscle over a period of several weeks, you can actually see the that the machinery necessary to burn triglycerides for fuel increase. You see expression of genes increasing that are able to use the fat. So, if you go from a standard 50 or 60 percent carbohydrate diet to fasting … your muscles are going to be weaker, because they're used to glucose. They're like, ‘Where's my glucose?’
You have triglycerides [but] you can't use it at first. Some people call it keto flu. But, over a period of about two weeks or so, your body gets used to it. So, an easy transition is to switch over to a very low-carbohydrate, high-fat diet, so that your body is used to using fat.
You’re not fasting per se, but your body gets used to burning fat for fuel. The other thing is you can start lengthening your period of fast. You should be fasting every day … Whether it's 12 hours or 14 hours. There should be a period in there that you're fasting. Then you extend it, so that you gradually go to 16 hours, 18 hours, 20 hours and then 24 hours, and then kind of go into it from there. Those are two ways to ease the transition and make the fasting easier …
Even shorter periods of fasting of 24 to 36 hours have a lot of benefits. You start to get into that period where you're depleting your glycogen and you're getting into fat burning. You start to see autophagy start around 24 to 30 hours as well. One of the other benefits people talk about nowadays is this sort of bio-hacking.
People, especially in Silicon Valley, are fasting because it gives them more mental capacity. Their brain works better; they find they're clearer and they can think better. So, this is a free way to boost your brain power. So yeah, there's all different regimens, and there's all different ways to ease into it. But the key is to just get started.”

How to Minimize Side Effects

Gradually easing into longer fasts will naturally minimize most side effects associated with fasting, as will transitioning over to a high-fat, low-carb diet, to help your body to adjust to using fat as a primary fuel. The so-called “keto flu” is often related to sodium deficiency, so it’s recommended to take a high-quality unprocessed salt each day. I typically pour salt in my hand and lick it throughout the day when fasting, as I obviously can’t put it on food. This will also help reduce the likelihood of intractable muscle cramps at night.
Headaches are also common when you first start water fasting. These too can often be minimized by taking salt. An alternative to eating salt straight, or putting it in water, is to add it to a bit of bone broth. Another important mineral is magnesium. It’s particularly important if you are diabetic, as magnesium deficiency is very common among Type 2 diabetics. This is another possible culprit if you’re getting muscle cramps.
There are several types of magnesium, some of which are more poorly absorbed than others. During water fasting, your best bet is to use Epsom salt baths, as this allows your body to absorb the magnesium through your skin rather than your digestive tract. Magnesium has a laxative effect in high doses, and when you’re not eating anything, oral magnesium can easily result in “disaster pants.” Multivitamins can also be useful during extended fasts, especially if you’re doing them regularly.
It is also important to understand that if you are on a multiday water fast you will liberate many toxins from your fat stores, so using an infrared sauna and taking effective binders, like chlorella, modified citrus pectin, cilantro or even activated charcoal can help eliminate these liberated toxins from your body and prevent their reabsorption.

Work With a Knowledgeable Physician if You’re on Any Medications

While fasting is a profoundly effective intervention for Type 2 diabetes, you do need to use caution if you’re diabetic. If you are taking medication, especially for your blood sugar, you have to make sure you talk to your doctor, because there's a risk your blood sugar may end up dipping too low. If you're taking insulin, and keep taking insulin while fasting, you could get into trouble.
“Some people say that for that reason, Type 2 diabetics should never fast. But that's not true,” Fung says. “What's true is that you need to adjust the medication in anticipation of [your blood] sugar going down … So, if you're on these medications for diabetes, you need to make sure you monitor very closely and make sure that your blood sugar doesn’t go too low.
Remember, the fasting is going to drive your blood sugars down, and your insulin or your medications will drive your blood sugars down, so you've got kind of two things driving your blood sugars down. All of a sudden you go low, you can have seizures, you can wind up in the emergency room and you could absolutely die.
And that's one of the things you have to be very careful of. So yes, you can do it, but you have to make sure you do it in a supervised setting with somebody who knows what they're doing.”

Why You Need Not Fear Starvation

Last but not least, one of the greatest fears people have about fasting is the concept of starvation and the loss of lean muscle mass. In his book, Fung explains why such fears are overblown. Your metabolic rate is the energy your body uses to generate body heat and keep your organs working. Your body basically needs a certain number of calories a day. People have a tendency to think that skipping a meal means your metabolic rate will decrease.
In reality, the exact opposite occurs. In studies looking at basal metabolic rate, people’s metabolic rate is actually 10 percent higher at the end of a four-day fast than at the beginning. So, your body is not shutting down, it's actually ramping itself up. The reason for this has to do with counterregulatory hormones. As insulin drops, counterregulatory hormones go up.
Some of these activate your sympathetic nervous system (the so-called fight or flight response). “So, as you fast, all these hormones are going up, your sympathetic nervous system is going up, your adrenaline is going up, your growth hormone's going up,” Fung says.
“Obviously, if you're pumping your body full of adrenaline, your basal metabolic rate is not going down. In fact, it maintains itself, which is in distinction to calorie restriction diets where, if you just try and cut a few calories a day, your metabolic rate will go down. The growth hormone is also important because of [its] protein sparing effect …
When you study people fasting, you don't see an increase in burning of protein. There is a normal turnover. But at the end of it, because your growth hormone is so high, when you eat again, you will make up these new proteins. So, it's actually much healthier for you because you're getting rid of all protein and you're bringing new protein.”