Fasting, by definition, is the willing abstinence from food or drink. Nearly every religious text will call for periods of fasting as a spiritual practice. Some fasts include all food and liquids, others allow for water and possibly light caloric broths. Fasting lengths can also vary from 12 hours to a matter of days.
Beyond the spiritual benefits, current research has shown there may be some significant health benefits. These include reducing inflammation, improving blood sugar regulation, reducing oxidative stress, improving the body's ability to handle stress, and modifying body composition (losing body fat!). Although both calorie restrictive diets and intermittent fasting may both result in weight loss, research appears to show that those who fast will maintain a greater percentage of lean mass. This is extremely important to understand. Many people who lose weight by restricting calories will lose both fat AND muscle. Fasting may allow for more significant percentages of fat loss. Win/Win!
Energy levels can also be enhanced through fasting. This occurs as a result of an increased insulin sensitivity. Insulin is essential for proper blood sugar regulation as well as energy availability and utilization. Elevated levels of insulin create inflammation and stimulate the body to store fat regardless of caloric intake. The mitochondria, the powerhouses of the cells, become more efficient and keep energy stores high when insulin is well controlled.
There are countless forms of fasting that have been practiced for centuries throughout the world. Two types of fasting that may be of most benefit are Intermittent Fasting and what I will call the 5:2 Fast (two non-consecutive 24 hour fasting days during each week). Because our body's have been trained to burn sugars through the modern diet, we tend to crave them on a regular basis. Fasting forces the body to burn fat as the primary fuel source. Because it contains twice the calories of carbohydrates, fat is a much more efficient source of energy. Please understand that fasting in not a diet, it is a pattern of eating. It's a way of scheduling your meals so that you get the most out of them. Fasting on it's own doesn't change what you eat, it changes when you eat.
Intermittent fasting consists of limiting food intake for an extended window each day. This generally involves a 12-14 hour time period of caloric restriction. Although this may sound somewhat extreme for some, it actually mimics what our ancestors likely experienced. More specifically, much of the world's population still eats this way. Unlike in many Western cultures, instantaneous access to food is limited for most people in the world. Although great value can be realized by making this a daily practice, even completing three days a week can prove beneficial.
So what does the research tell us in regards to intermittent fasting?
"Salk scientists fed groups of adult male mice one of four diets: high-fat, high-fructose, high-fat and high-sucrose, and regular mouse kibble. Some of the mice in each dietary group were allowed to eat whenever they wanted throughout their waking hours; others were restricted to feeding periods of nine, twelve or fifteen hours. The caloric intake for all the mice was the same.
Over the course of the 38-week experiment, some of the mice in the time-restricted groups were allowed to cheat on weekends and eat whenever they chose. A few of the eat-anytime mice were shifted to the restricted windows midway through the study.
By the end, the mice eating at all hours were generally obese and metabolically ill, reproducing the results of the earlier study. But those mice that ate within a nine or twelve-hour window remained sleek and healthy, even if they cheated occasionally on weekends. What’s more, mice that were switched out of an eat-anytime schedule lost some of the weight they had gained."
(See the attached link to view the graphic to give you a better visual).
The other form of fasting is know as 5:2. You eat regularly for five days in a weeks span, interspersing fasting two whole non-consecutive days (which consists of limiting caloric intake to about 600 calories for men and 500 calories for women). Here is what one study revealed:
"Researchers at the University of Manchester found that when overweight women followed a 5:2 approach, they lost more weight and body fat and improved their insulin resistance compared with women who followed a more traditional diet of limiting calories seven days per week. One explanation for the success of the 5:2 dieters could be that a day of mini-fasting can lead to a diminished appetite. There may be an evolutionary explanation for this because humans (and other animals) have fasted intermittently for much of our time on Earth. As a recent paper in the Proceedings of the National Academy of Sciences notes, "The most common eating pattern in modern societies, three meals plus snacks every day, is abnormal from an evolutionary perspective."
Although fasting can be an effective way to reset your metabolism, eating nutrient dense, unprocessed food as well as eliminating sugar are essential if you want to optimize your health. Some of the research notes that improvement was seen regardless of nutritional quality of the foods consumed. In my opinion it would make no sense to undergo fasting to improve your body composition while eating foods that wreck your health by stimulating oxidation and inflammation. Why not incorporate lots of fresh vegetables, some fruit, healthy fats such as coconut oil and olive oil as well as nuts and seeds? Add in organic eggs along with organic sources of meats. While you're at it, lose the dairy and the grains! I assure you, within a month you WILL notice a difference in your health.
Would you be interested in adding more fuel to the fasting fire? Include some exercise. Any exercise will help, but I am a big fan of high intensity exercise. This does not mean it has to use heavy weights, it simply requires increasing the intensity of your activity to get your heart rate up to higher levels. This type of exercise is of a much shorter duration, but much greater intensity (awesome news for those where time is a challenge!). As you have likely heard before, always check with your doctor to see if high intensity exercise would be appropriate.
To summarize, here are a few reasons why I believe fasting is of benefit:
- Improved mobilization of fat for fuel.
- Rejuvenation of the mitochondria (cell powerhouses).
- Stabilization of blood sugar.
- Improved insulin sensitivity.
- Resets the hunger stimulus threshold.
- Research shows calorie restriction increase life span.
- (fasting stimulates these same mechanisms without feeling like you are starving yourself)
If you are interested in incorporating fasting into your routine, check with your doctor. With my patients, we incorporate an in-depth blood chemistry that reveals nutritional imbalances that may need to be supported prior to fasting in order to maximize health. This also allows us to retest and monitor physiological improvement. Here is an example of the 20 page Doctor's Choice Functional Health Report our patients receive at no additional cost. I can assure you that it will be like no other lab report you have ever seen!
The use of fasting as an alternative to calorie restriction is more than a fad diet, although it is important to remember that one size does not fit all. I would not recommend fasting if you are pregnant or for children unless under qualified supervision. As for the rest of you, give it a month and see how you feel. What have you got to lose except a few pounds?