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.
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.
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.
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:
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.
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