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Fasting with food

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The latest craze is a diet that mimics fasting, but does it work as well as the real thing? Cate Montana investigates

In today’s toxic world, it’s the rare individual who doesn’t present with an overburden of chemicals and pollutants in their body. Subtle signs of toxic overload include chronic fatigue, bad breath, coated tongue, edema or excess water weight, chronic infections, headaches, sinus problems, indigestion, bloating, gas, dark circles under the eyes, yellowing of the skin, diminished sex drive and overall depression.

And then there’s the epidemic of obesity. Worldwide, the number of adults and adolescents who are considered overweight or obese is exploding. In 2022, about 2.5 billion adults around the world were assessed as overweight.1

Fasting has a long history of use to address both toxicity and obesity, starting with the father of medicine himself, Hippocrates, back in the fifth century BCE. Traditionally, fasting has been the complete elimination of all food and drink except pure water for an indeterminant period of time—usually lasting in proportion to the degree of toxicity and illness it’s designed to mitigate.

Although many people think fasting is just a matter of not eating for a few days, this is far from the truth. Fasting is a science and an art. Just as there are all kinds of people with all sorts of different biochemical compositions, physiological constitutions and health issues, so there are loads of different fasting/cleansing approaches and regimes to use.

Depending on the situation, a person might do a water-only fast, a juice fast, a modified fast that includes vegetables (raw or cooked, depending on the person’s needs) or another type. And to ensure it’s effective, there is a strict protocol for any kind of fast—a proper way to introduce the body to the fast, the fast itself, and then the all-important process of ending the fast.

“Unfortunately, the vast majority of physicians, even naturopaths, have not received any education or gained any experience in nutritional therapy, herbal cleanses, detox diets and fasting,” says Dr Andrew Iverson, ND, a natural foods, detox and fasting expert (

“Most naturopaths and holistic-minded physicians have resorted to prescribing processed ‘detox powders’ formulated by supplement companies on the naive assumption that they are putting their patient on a ‘cleanse.’ I have worked extensively with whole-food diets and cleanses and with thousands of patients for 30 years, and believe me, a powdered ‘detox in a can’ is not going to do anything compared to a nature detox with real, live juices and broths.”

Overcoming resistance

 In addition to the fact that most doctors are unfamiliar with fasting and cleansing practices, there is public resistance to the very idea of fasting itself. Even though studies consistently show the power of fasting and its positive impact on bodily functions like lipid metabolism, glucose metabolism, protein metabolism and neuroendocrine metabolism as well as its powerful mood-enhancing effects,2 fasting has become “antiquated.”

Studies show reduced insulin dosages for patients with diabetes who do intermittent fasting,3 and they show that fasting—even intermittent fasting—reduces obesity, cardiovascular disease, cancers and neurological disorders.4 Still, people accustomed to walking down the grocery store aisles and picking from thousands of brightly colored, sugar-laden, chemical-laced, flavor-enhanced processed foods, chips, candies and snacks have a hard time wrapping their heads around the concept of refraining from food altogether.

“We talk about this as the pleasure trap,” says water-fast expert Dr Alan Goldhamer, founder of TrueNorth Health Center ( “The chemicals we put in our food that fool our brain, like salt, oil and sugar, are highly fractionated food byproducts, not food. And they artificially stimulate a dopamine cascade in the brain.

“They make food taste better and more interesting to us. As a consequence, we systematically overeat. It’s the hidden force that undermines health and happiness. And because people don’t recognize the trap, it’s very difficult for them to take action.”

Iverson agrees. “The most powerful thing you can do for your body, and the least likely thing that people in Western nations will actually do, is fast from food.”

Which is the main reason Dr Valter Longo, researcher and director of the Longevity Institute at the University of Southern California (, developed the five-day fasting-mimicking diet (FMD). This five-day plant-based, low-calorie, low-protein diet includes only moderate amounts of carbohydrates and fats, and he claims it mimics the effects of fasting.

“The body is always fed,” says Longo. “Sometimes it is fed from the outside, and sometimes it’s fed from the inside—and the trick is obviously confusing the brain about the source. The body has to recognize the food as coming from an internal source and not an external one.

“After a couple days of not getting fully fed, the body switches to using the stuff around the belly. The body is happy to use the fat, although it will pull some protein from the muscle. Basically, the fasting-mimicking diet allows the natural process of starvation to occur, with autophagy, protection and stem cell regeneration (see health benefits below).

“You don’t interfere with the body’s natural processes with this diet. That’s the key.”

Potential health benefits

These are some potential health advantages of following the five-day FMD.

Metabolic reset. The main focus of the fasting-mimicking diet is long-term metabolic health improvements, which can mitigate and even prevent negative health conditions like diabetes, high blood pressure, high blood sugar and obesity. In one study, subjects who consumed the FMD for five consecutive days per month for three months reduced body weight, trunk fat and total body fat; lowered blood pressure, fasting glucose and total and LDL cholesterol; and decreased insulin-like growth factor 1 (IGF-1). In other words, it corrects metabolic syndrome.5

According to Dr Longo, the FMD can prompt a metabolic reset, enhance insulin sensitivity, reduce inflammation and rebalance hormones. Short-term weight loss may also occur, but weight loss is not a primary goal or benefit of the diet.

Detoxification. The reduced food intake leads the body to more effectively process and eliminate toxins stored in fat cells. This directly improves overall organ function.

Autophagy. The diet can trigger a cellular process called autophagy during which the body eliminates damaged and non-working parts of a cell and recycles them for cellular repair.6 This cleanup process improves cellular function throughout the body, helping to increase overall health and well-being.

Deep healing. According to Longo, one of the major benefits of the FMD is that the five-day period of reduced caloric intake gives the body a break from constantly having to digest foods and manage nutrient assimilation. This break in the routine allows energy to go toward repairing tissues and addressing underlying health issues.

Longo recommends using the diet once a month for three consecutive months to reset the body’s metabolism, detox and start developing proper eating habits instead of overconsuming. Between the five-day FMD sessions, he recommends following the Longevity Diet, a mostly plant-based diet that includes seafood two or three times a week.

Studies show the FMD reduces insulin resistance and fat in the liver as well as signs of aging. Doing the FMD three times in three consecutive months can lead to a median 2.5-year reduction in biological age.7 It also reduces the risk factors for aging and for age-related diseases.5

As well, the diet normalizes blood glucose levels, improves insulin sensitivity and boosts cellular function in mice.8 And it improves metabolic syndrome in patients with type 2 diabetes.9

It also boosts antitumor immunity in patients with cancer.10

“Scientists are wary of the word cure because it sounds like an exaggeration,” says Longo. “However, for some patients with type 2 diabetes and for the great majority of prediabetic patients, the combination of the dietary interventions of the periodic FMD plus the Longevity Diet could eventually free them of type 2 diabetes, especially if treatment begins right after the initial diagnosis when the pancreas is still functioning well.”

When to be wary of fasting

Any fast or calorie-restrictive cleanse, from a water-only fast to the five-day FMD, should be done under the advisement and supervision of a physician or trained health practitioner. Of most concern are people on medications who have preexisting conditions such as these:

  • Ulcers
  • Anemia
  • Osteoporosis
  • Kidney stones and gallstones
  • Kidney disease
  • Diabetes
  • Heart issues or atherosclerosis
  • Heart attack
  • Liver disease
  • Neurological conditions
  • Late-stage terminal illness
  • Substance addictions

Warning: Under no circumstances, not even strict supervision, should a pregnant, lactating or breastfeeding woman undergo a fast or cleanse. As well, anyone suffering from anorexia, bulimia or another eating disorder should never engage in this practice.

Stay well hydrated

Water is the main liquid to consume during a cleanse, along with herbal teas, veggie juices, soups and broths.

To determine your daily water volume, divide your weight by two. For example, if you weigh 180 pounds, then half of 180 gives you 90 oz (2,660 mL).

Start with a full glass of water when you wake up and sip water between meals throughout the day. Refrain from drinking water at least 15 minutes before a meal and for at least 30 minutes after a meal to allow your food to digest properly.

The source may be fresh spring water, freshly distilled water or fresh filtered water (filtered by kinetic degradation fluxion, reverse osmosis or similar). Do not store your water in plastic but rather in glass or stainless steel. It’s obviously healthier to filter your own water than to buy it from a company that has it constantly stored and delivered in plastic containers.

Take it easy

According to detox/fasting experts, rest is imperative during any fast or cleanse. You should aim to get no less than eight to 10 hours of sleep every night of the cleanse, preferably in a well-ventilated room or using an air purifier if possible. While on a fast, be sure to get out in the fresh air and do some daily deep breathing and/or sunbathing.

Do not exercise! Gentle walking and stretching or using a mini-trampoline rebounder (for gentle rebounding, not a cardio workout) are okay. Rest emotionally and intellectually by avoiding highly stimulating movies and sports, intensive reading, violent video games, etc.

Weight loss

One of the major reasons most people fast is because they want to lose weight rapidly. And although fasting is almost guaranteed to help you quickly shed some pounds, most people just as quickly gain them back.

“Fasting is miraculous,” says Iverson. “The problem with fasting is sooner or later you have to eat. And that’s where all the problems lie. You see, the ‘refeeding’ element of a fast is more important than the fasting itself.

“If you don’t reengage food in a way that supports the fasting you did, then not only do you eventually undo what you’ve done, but you really don’t see any long-term benefit at all.”

Coming off the FMD

According to Longo, it’s enough to minimize or eliminate consumption of fish, meat, saturated fats, pastries, sugar and dairy for 24 hours after completing the five-day FMD. But Iverson says it’s well worth it to be even more conservative as you ease back into eating regular food. After all, you want to do everything you can to support and potentize all the good work and effort you’ve put into sticking to this fast or cleanse in the first place.

“Knowing how to break the cleanse properly is more important than being on the detox itself,” says Iverson. “If you want to maintain the benefits you gained, the simple rule is to break the cleanse in the opposite way you went into it.

“Spend at least one day in each level, in whichever phase you choose, allows the body to slowly readjust to eating and prevents the body from overeating and undoing all the benefits you just accomplished. This gradual working into and out of a fast slowly refeeds the body to appreciate and desire healthy foods again, which prevents the ‘yo-yo’ dieting responses. It also systematically readjusts the hormones gradually to prevent the unwanted weight from returning.”

So, stick to basics for at least one day coming out of the five-day FMD. Increase your caloric intake and try adding some whole grains to your diet that first day. Add in fruits the next. Wait until day three to reintroduce proteins, and then do so in the more easily digestible form of fish or chicken.

“Grains, nuts, seeds and legumes along with animal protein like eggs and fish are not considered cleansing foods,” says Iverson. “Rather they are building foods to support you after you have cleansed. More time spent in a state of health and healing means more powerful results, and if you break this cleanse slowly, the results will be long-lasting.”

Eating advice for life

Both Longo and Iverson recommend that people over age 35 consider dropping from three meals a day to only two. Iverson takes it a step further and, contrary to popular nutrition advice, recommends that most people not eat solid food when breaking their fast in the morning. (That’s why breakfast is called breakfast!) Instead choose a caloric drink that’s high in nutrition but has no dairy in it—such as an antioxidant smoothie.

“That’s the way to really start off your day,” he says. “I also recommend drinking 12 ounces of pure water first thing, with a quarter of an organic lemon or lime, with the rind. This will help clean out your liver and provide the antioxidants that are needed to get you through until lunch.”

Iverson, Longo and Goldhamer all maintain that the point of fasting is to cleanse and reset not just your body’s metabolism but your entire relationship with food so you can start eating in a healthier way. “That’s how you win,” says Iverson. “You do the diet and then find the healthiest foods that work best for you afterwards and stay with it.

“But if you do the fasting-mimicking diet and then you go back to eating the way you were, and then you do the fasting-mimicking diet again a month later, you’re going to have this yo-yo-like effect. Sure, it’s going to be better than eating poorly all the time, but you’re never going to heal and get to where you want to be.”

Pre-cleanse quiz: Determine your body type

Before you decide to do any fast/cleanse, including the fasting-mimicking diet (FMD), it’s vital to determine your fundamental body type, says Dr Iverson. According to Traditional Chinese Medicine, there are two major body types: yin dominant and yang dominant.

Everybody embodies both yin and yang qualities—which are often described as feminine (yin) and masculine (yang). However, every person is usually predisposed to exhibit more of one or the other. As well, most people experience an excess or deficiency of one of them.

The point of taking this short quiz (which can also be found in Iverson’s book Nature’s Detox, Trilium Health Press, 2017) is to determine how your body is currently expressing yin/yang energetics so you can tailor your cleanse or fast for the best possible results and the least amount of stress.

Read the statements below and make a note of how many best describe your body. Only count the statements that are a good match for you.

Yin dominant

The following are some traits of an individual who is in a state of yin dominance.

  • Feels cold most of the time and/or has a lower body temperature
  • Underweight or has difficulty gaining weight
  • Low blood pressure or low electrolytes on lab results
  • Lives in a cold climate at the time of the cleanse
  • Tends toward anemia (pale skin), osteoporosis, hypothyroidism, hair falling out
  • Infrequent or absent menstrual cycles (women only)
  • Personality: quiet, shy, introverted

Yang dominant

The following are some traits of an individual who is in a state of yang dominance.

  • Feels warm or hot most of the time and/or has an elevated body temperature
  • Overweight or gains weight easily
  • Tendency toward a red complexion, hypertension, diabetes, gout, kidney stones
  • Elevated blood pressure, cholesterol, triglycerides or blood sugar
  • Lives in a warm climate at the time of the cleanse
  • Personality: outgoing, extroverted, easily frustrated or irritated

If you’ve totted up three or more in either group, then you can classify your type as either yin dominant or yang dominant. If you are neither, then just follow the general parameters of the five-day FMD, ignoring the following fine-tuning points:

If you are yin dominant

  • Stay warm by turning up the heat or dressing warmer
  • Drink room-temperature water and juices but no cold drinks
  • Drink hot teas, broths and soups
  • Eat cooked veggies
  • Include bitter flavors and acidic foods (like bitter herbs and lemon)

If you are yang dominant

  • Keep cool
  • Drink cool (but not icy) water and juices
  • Drink cool herbal teas
  • Eat raw veggies

The most cleansing foods

Below is a list of foods in order of most to least cleansing. Water taken alone, of course, is considered the most cleansing form of detox. In fact, a true fast is by definition a water fast. Any introduction of caloric substances is actually a “modified fast” or “restricted diet” rather than a true fast.

“Modified fasting on juices and fruits is less extreme than water fasting,” says Iverson, “and modified fasting on raw or cooked vegetables is less extreme than just eating grains, nuts, seeds and legumes.

“Of course, protein is not really a cleansing food at all. It’s a building food, which is why it is removed from the diet prior to starting a cleanse and is not reintroduced until a few days after.”

  • Pure water
  • Veggie broths
  • Veggie juices
  • Raw fruits
  • Raw veggies
  • Cooked fruits and veggies
  • Cooked starches: root vegetables, then grains, then beans
  • Vegetable fats: avocado, olive, then seeds and lastly nuts
  • Proteins (build tissue)

Going into your fast

Iverson highly recommends preparing for your five-day fast by eliminating such foods as meats, eggs, dairy, alcohol and caffeine from your diet for at least one day prior to starting the fast. Up your intake of water and juices.

And, tempting as it might be to stuff yourself before you start fasting, don’t. Slamming into a fast overnight will make it even harder to start and maintain the fast, plus it’s simply not kind to your body. 

The five-day FMD

Day 1: 1,100 calories total (11% protein, 46% fat, 43% carbohydrate)

Complex carbohydrates: 500 calories (from veggies such as broccoli, tomatoes, carrots, zucchini, pumpkin, mushrooms)
Healthy fats: 500 calories (nuts, olive oil, avocado)
Plant-based protein: 25 g, mainly from nuts
Herbal teas, unsweetened, up to 4 cups per day
Pure water: see above
One multivitamin and mineral supplement
One omega-3/omega-6 supplement

Days 2–5: 800 calories total (9% protein, 44% fat, 47% carbohydrate)

Complex carbohydrates: 400 calories from veggies above
Healthy fats: 400 calories from fats above
Plant-based protein: 25 g, mainly from nuts
Herbal teas, unsweetened, up to 4 cups per day
Pure water
One multivitamin and mineral supplement
One omega-3/omega-6 supplement

FMD recipes

For those who don’t want to crack out the kitchen scale, count calories or chop veggies, Dr Longo has developed a five-day FMD meal package called the Prolon 5-Day (US:; UK: For $195 (£189), you get a box containing freeze-dried soups, nut bars, fruit-flavored drinks, teas and supplements—all precisely measured for calories and proper proportions of protein, carbs and fat.

However, if you want to maximize nutrition during the fast, it’s hard to beat fresh organic vegetables, legumes, nuts and fruits from the farmer’s market. Follow Dr Longo’s recommended caloric guidelines for fats, carbs and protein.

Here are some sample recipes:

  • Lentils with green beans, onions and spices cooked in olive oil
  • Vegetable stir fry with leeks, broccoli, onion, and mushrooms sauteed in spices and olive oil
  • Sweet potato cooked, cooled, and then reheated to increase resistant starch and slow sugar absorption, then topped with chickpeas, onion, arugula and spices
  • Chopped fresh tomato, cucumber and avocado drizzled with olive oil, salt and pepper, and a rice cake
  • Sliced carrots, garlic, onions, grated ginger and coriander fried in olive oil plus 8 oz water or vegetable stock, cooked until translucent and blended into a soup, then reheated with 7 oz unsweetened low-fat coconut milk

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