When you fast, you forego food for a designated period of time. Almost every culture and nation has practiced fasting at some point or other. Sometimes it’s been incorporated into a religious tradition. Other times, individuals have used it to express their opposition to a political situation. And many cultures have used the fast as a medical tool.

Advocates of fasting emphasize how good it is to give the body a break now and then from the stressful process of digestion. Fasting allows the liver to more effectively detoxify the cells, which can become overloaded with toxic byproducts of the metabolism. After a fast, your digestive tract is free of toxins, pathogens and waste matter, allowing you to make optimal use of nutrients consumed.

Detractors insist that the body is designed to dispose off toxins by itself without the need for a fast; that the body is exhausted of its calcium and protein during a fast, which can result in osteoporosis and muscle decomposition; and that fasting reduces the resting metabolic rate, which translates into rapid weight gain once the fast is over.

Remarkably, scientific animal studies have proven that restricted-calorie diets increase longevity. New research suggests that a reduced calorie diet combined with intermittent fasting results in a longer, healthier life for humans as well.

How Do We Define Intermittent Fasting?

It is the continuous and repetitive process of eating normally for a certain amount of time and subsequently fasting for a period of time. When you fast intermittently, you alternate between periods of non-fasting and fasting.

What Makes an Intermittent Fast Superior to a Traditional Fast?

First, intermittent fast is not about eating or avoiding specific foods, therefore you eat what you enjoy during non-fasting times. This is very important if you consider that most diets fail because they deprive people from their favorite foods. With intermittent diet you don’t get “diet fatigue” because you are not fasting continuously. Another advantage is that you don’t have to worry about counting calories. You just restrict them all at once during the fasting periods.

A great factor in favor of intermittent diet is its short duration. Because each fasting segment does not last more than 24 hours, your metabolism doesn’t have a chance to slow down. Furthermore, unlike tradition fast, you don’t worry about entering into starvation mode, which would be catastrophic for your muscles and your health in general. Finally, the short duration of intermittent diet eliminates the risk of nutrient depletion and ensures that your energy levels are not reduced. For all these reasons, intermittent fast is better than usual fast.

What Is the Impact of Intermittent Fasting on Health?

Excess weight increases the risk of several diseases, such as cardiovascular disease, diabetes and certain forms of cancer, to name a few. Overweight people who restrict their food intake and lose some of their excess weight lower significantly their chances of suffering from any of these diseases.

Here is the problem, though. Continuous energy restriction is not a sustainable form of dieting. Continuous food deprivation is actually the main cause dieters never get to comply with a diet for more than a few weeks or months at best.

Studies have shown that fasting in short spells separated by longer periods of habitual (ad libitum) food intake is equally or more effective than continuous energy restriction. Sounds complicated? Simply put, there is evidence that it’s better to abstain from food two days a week and eat at pleasure (but sensibly) the remaining 5 days of the week, than just restrict yourself to following a low calorie diet everyday.

Studies conducted in animals over the last 8 years have shown that intermittent fasting:

• Reduces age-related cognitive impairment
• Protects the heart
• Improves insulin sensitivity
• Prevents tumorigenesis
• Delays the onset of prostate cancer
• Prolongs survival
• May have beneficial effects in the pathogenesis and treatment of multiple sclerosis

Researchers from the Stanford Medical School in California, noted health benefits that began in test animals in as little as two weeks after the commencement of an alternate-day fasting program. Their summary included a long list of disease conditions alleviated by intermittent fasting, and they suggested that this pattern of eating could be effective as a weight loss strategy.

For the study, rodents ate restricted calorie diets on one day, consuming less than half of their estimated daily requirement. The following day, the test animals were allowed to eat as much food as they desired. The research team noted marked health benefits. The list included resistance to allergies, asthma, infectious disease, rheumatoid arthritis and other autoimmune disorders, cardiac arrhythmias, and menopause related hot flashes. Insulin resistance was also improved. Further, the animals’ cognitive ability got better and they were impacted less by acute stress.

BDNF (brain-derived neurotrophic factor) levels were also found to have increased. This chemical is a neurotrophin that allows certain sections of the adult brain to grow new neurons. Humans with high levels of BDNF are less depressed and more intelligent. When test animals have been injected with BDNF, they experience improved insulin sensitivity, which allows them to lose weight. BDNF is a desirable brain chemical, which can be increased through intermittent fasting.

How Do I Perform an Intermittent Fast?

Although there are a number of different ways, three types of intermittent fast are the most popular.

1. Daily Fasting Method

On this protocol, food intake occurs for a block of time during the day. The popular Fast-5 Diet is a type of daily fasting. All foods are allowed, but they must be eaten during a 5-hour window (from 5 pm to 10 pm, for instance.) Fasting continuously for 19 hours is the key to this diet’s effectiveness. The intestinal tract remains empty for long periods of time and insulin levels are reduced. You won’t see significant weight loss until you’ve been on this diet for two weeks. After that, you should lose weight at the rate of about a pound per week.

2. “Eat Stop Eat” Method:

You devote one, two or three non-consecutive days of the week to fasting and exercise. The rest of the time you eat normally without restriction. When you fast, you consume water and black coffee exclusively. One pound of body fat is equivalent to 3500 calories. By alternating normal food consumption with a day or two of fasting, your weekly caloric consumption is decreased by at least 3500 calories. That means you lose minimum 1 pound a week.

3. Alternate Day Fasting Method:

On this protocol, there is one day of eating followed by one day of fasting. A technique that ensures that you never go an entire day without food is as follows: Start your fast after you have eaten dinner early, say about 6 p.m. The next day, you won’t eat until 6 p.m., at which point you’ll have dinner and start your day of eating. This fast has a couple of benefits. For one thing, it’s an easy way to ease into intermittent fasting. For another, you’ll enjoy health and weight loss benefits, while minimizing the sense of dread you might experience about the upcoming fast.

It appears that intermittent fasting can’t be beat for real long term weight loss and health. If you combined intermittent fasting with eating low carbs between the fasting periods, it wouldn’t be an overstatement to call yourself a fat furnace!

Matthew Papa, PhD, is a biologist and writer who eagerly reads and writes about healthy eating, diets and weight loss programs supporting his views with relevant scientific references. In his blog, he features diet programs that have been subjected to quality clinical studies and provides a Weight Watchers promotion coupon and a savings coupon for eDiets.

Image credit:  Alan Cleaver

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What is the Definition of Fasting?

Fasting is the act of willingly foregoing food for a period of time. Before the advent of agriculture, our ancestors had no choice but to abstain from food when food was scarce. During times of feast, excess calories are stored to tide the body over during times of severe food shortage.

Tell Me a Reason Why I Should Fast

Fasting gives your body a much-needed break from the stress of digestion. Today, about half of all Americans are overweight. This implies that a great number of people are consuming too many calories every day. These are mostly calories without nutrients. Overconsumption of empty calories stresses the liver and kidneys, which are responsible for filtering out toxic substances, and creates an accumulation of food waiting to be processed. Toxins are stashed in fatty tissue, to be dealt with later. When you stop eating for a period of time, you give your body a chance to catch up, to heal and repair the damage.

The Physiology of Fasting: Ketosis

Your body needs energy in the form of glucose in order to survive. Glucose is produced by the break down of glycogen, which is made by and stored in the liver and muscles. During the first day of a fast, almost all glycogen reserves are used up. At that point, fat is used in a process called ketosis. For women, it begins on the second day of fasting. For men, it’s the third day. During ketosis, the body breaks down fat molecules for energy. Until the body enters ketosis you may feel hungry and energy depleted. Once ketosis is established, you will feel that your hunger pangs are minimized, mental alertness is restored and energy levels increase. Evelyn’s fasting experience attests to this.

Am I Going to Starve?

The amount of time a person can fast varies depending on the needs and goals. You should never fast to the point were starvation kicks in. Starvation occurs when the body has to use vital tissues to sustain life, because all of the stored energy sources (carbs and fat) have been depleted.

Will I Suffer Muscle Loss?

Some muscle loss takes place mainly on the first day of a fast. When you stop eating, the body converts muscle tissue into glycogen. This process does not continue, though. The brain alone would require the conversion of a pound of muscle tissue per day in order to function. By shifting to ketosis, the body preserves muscle mass and taps into its fat reserves.

How Much Fat Will I Burn?

In the initial phase of a fast, it may seem like you’re losing weight quickly, but that’s because most of the weight you have lost is water. In fact, it’s important to drink plenty of water while fasting, to avoid dehydration. Once your body enters ketosis, you can expect to lose about 3-4 pounds of fat per week.

How Long Does a Fast Last?

Typically, a fast does not take more than just 1-3 days. Generally, it is not safe to fast for an extended period of time unless you receive medical guidance. It is not uncommon for advocates of non-conventional medicine to fast for half or even a whole month in an attempt to treat long-lasting ailments.

Is Fasting to Lose Weight Considered Healthy?

Experts’ opinions differ on this issue. Some say that fasting should not be attempted at all. Others point to the multiple health benefits they have witnessed as a result of fasting. Each side of the issue has credible arguments.

One expert in favor of fasting is Joel Fuhrman, M.D. He wrote a comprehensive book about the subject called Fasting And Eating For Health. He and other fasting enthusiasts list these upsides:

• Since the American diet is deficient in nutrients, the body cannot free itself from toxins on its own and needs assistance. When you eat empty calories, but also through normal metabolism, your cells accumulate oxidizing substances. This condition leads to premature aging, as well as vascular disease, diabetes, and vital organ deterioration. By fasting, you give your body the opportunity to purge waste products.
• Overweight and obese individuals have difficulty ‘just saying no’ to poor food choices. Fasting can change your relationship with food, and gradually enhance discipline.
• Some persistent conditions associated with obesity do not respond to conventional treatments. Fasting for just four days per month can have beneficial effects.
• Scientific research has proven that periodic fasting combined with a calorie-restricted diet lengthens longevity.

Those who oppose fasting for weight loss list these downsides:

• When you go without food, your resting energy expenditure slows down by as much as one fifth. When you begin eating again, the slower metabolism makes your body more vulnerable to weight gain.
• The ultimate goal of a weight loss program should be a healthier lifestyle that includes reduced calories and increased activity, not drastic measures such as going without food.
• Calcium and protein are two essential nutrients that your body cannot live without. If you’re not getting protein in your diet, your body resorts to muscle mass. If you’re not consuming calcium, your body will take it from your skeletal system, which may cause osteoporosis.
• Most people don’t drink enough fluids during a fast and wind up becoming dehydrated.
• Building up muscle mass is a desired outcome because muscle boosts your basic metabolism, which means that your body burns more calories while at rest. Fasting goes against this goal, since it leads to muscle mass loss, to significant degree sometimes.

So with equally persuasive arguments on both sides of the issue, should you make fasting part of your plan of action to lose weight? One thing to remember is that all of that extra fat on your body is storing toxic material that needs to be dealt with sooner or later. If you’ve noticed that you often seem to develop a collection of unpleasant symptoms while on a diet – such as a headache, rash, runny nose, and aches that feel like the flu – that could be your body catching up on its detoxification every chance it gets.

Fasting allows you to plan for that ‘healing crisis’ by designating a day to forego food, drink plenty of liquids, and get lots of rest. Once the fast is over, although your metabolism will be slower, your digestive tract will be cleaner and will use fuel much more efficiently.

How Do I Fast Safely to Lose Weight?

It is advised that you do not try fasting for longer than three days without a doctor’s supervision. For short fasts, it’s still a good idea to have someone monitor you. If you have serious health problems or if you’re taking medication, consult your doctor before embarking on a fast.

It is recommended that as you approach the day of fasting you progressively decrease the amount of food you consume. As a first step, stop eating all meat and dairy. The next day, eliminate beans, grains, and nuts. On the eve of the fast, eat only light foods – soup, salad, and fruit. Reverse this process after you finish fasting by incorporating heavier foods incrementally into your diet. And of course, drink lots of pure water during the fast, to avoid dehydration and flush out toxins.

If traditional fasting for weight loss has both pros and cons, then how can one decide whether fasting, as a means to shed pounds, is good or bad? Is there a way of fasting that eliminates the cons and multiplies the pros? Sure there is! It is called Intermittent Fasting—a clinically studied and well-research type of fasting, which I am going to talk about in my next guest post (coming tomorrow).

Matthew Papa, is a biology scientist who is enthusiastic about current research findings in the field of nutrition, diets and weight loss programs. He enjoys writing articles that present both sides of the coin on diet-related topics. In his blog, among other things, Matthew makes available a Medifast discount and a promotion code for Nutrisystem, two clinically studied meal replacement diets.

Image credit:  Alan Cleaver

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