The Benefits of Fasting

It is not often that I get an assignment for a specific article from my TW editor, Peggy, but when I do, I am always pleased to oblige, for I feel that she has the knack of knowing what is important and likes to give this to her readers. Such is the case with an international bestseller by Dr. Michael Mosley entitled The FAST Diet 5:2. This book describes a diet which involves fasting on an intermittent basis two days of each week. 

Fasting can either be elective or forced in humans or animals over the past or present. For example, a lion on the plains of Africa will make a kill and then eat for 2 or 3 days until satisfied, after which he sleeps for 2-3 days and then fasts until the next hunt. During fasting, the lion loses weight and becomes hungry and is ready for the next hunt. Our Paleolithic ancestors did the same thing, supplementing with some plant food such as nuts and berries until their next successful hunt.

So where do we fit in with this today? We know that fasting has been with us throughout history. Christians, Jews, Buddhists and Muslims, for example, practice fasting as part of their religious traditions. Catholics partially fast on Fridays, the 40 Days of Lent are a partial fast, there is a fast with Ramadan (one month), and fasting is also practiced by Buddhists (varied) and Jews (seven days). Gandhi fasted for 21 days and finally broke the fast when the British gave concessions for freedom to India. He stated that fasting was the most important way that you could be in total control of your body, and he easily survived this fast.

There are various approaches to fasting which include partial, intermittent occasional, 5 days on/2 off, and alternate day fasting. The benefits of fasting include lowering of carbohydrate intake (with weight loss), reduction of oxidative stress and cell inflammation, improved sense of vision and hearing, more mental clarity, more energy, more ability to relax, higher serum levels of human growth hormone, and some benefit to chronic degenerative diseases. If weight loss is the goal, it is a reliable technique to use.

Reduced food intake in this country can either be forced (relative starvation from lack of food and nutrients) or elective, which could involve any one of multiple diets which are popular. Most of these diets are different, but there are some similarities: diets such as Weight Watchers, which limit calories; the Zone Diet, which recommends eating types of food and quantities; simple caloric restriction, which is reliable, but hard for many to do; the Atkins diet, which is high protein/low carb; or the simple elimination of fat, carbs, or protein on a partial or complete basis. The average daily calorie intake in the US is about 2,450, usually more than needed.

The media influences our concepts for or against certain diets. “Low fat” diets are promoted on the false assumption that fat actually makes you fat. However, when you reduce fat in foods and you eat only a minimal amount of protein, the carb content will stimulate increased insulin output, making you add fat. This is what has happened in the U.S. in the last 10-15 years with the low-fat diet approach. The amount of calories consumed and average body weight has increased every year. 

One of the most sensible dietary approaches is the elimination of “white” products such as sugar and processed grains, which is effective in eliminating extra calories. Interestingly, if you fast and eat only “empty calories,” you will not thrive. For example, in the shipwreck stories from centuries ago, it was noted that if you were starving except for rations of rum or sugar, you would die sooner than if you have only water to drink. No food (water only) is better than bad food including sugar, flour, and alcohol. 

The FAST 5:2 diet includes five days of food and two days of relative fasting (but not on consecutive days). The two fasting days are limited to 400-500 calorie intake. Continuous fasting involves long-term caloric restriction on a daily basis and has the potential to impart better health and energy as long as it is not too severe and is accompanied by intake of adequate nutrients. However, most people will not follow this pathway. The FAST Diet is more user-friendly, as you do have only two low-calorie fasting days and can look forward to five days of eating normally. Weight loss is one benefit, but you can also reduce your risk of diabetes, heart disease, and cancer.

I think that the influence of the media in diets has been widespread and has confused a lot of people. Misinformation about certain proteins, the value or danger of fats, what low or high carbs can do, and whether or not a protein diet is healthy—these are just some of the issues being discussed in the press and the newspapers. Then there are ads like the Heinz ketchup ad: “80 billion French fries can’t be wrong.” This combination includes hydrogenated and transfat, potatoes with poor nutrient value, and tomato-based ketchup with high fructose corn syrup and excess salt. 

It is absolutely clear to everyone who deals with nutrition and diets that if you reduce your caloric intake to a low level, you need to keep the nutrient levels up. For example, if you take 1500 calories a day and you are eating half of this as sugar, starch, snacks, hydrogenated fat, and low-nutrient items, then you are not getting the daily requirement of nutrition. Also, if you reduce your calorie intake by cutting down on fats and protein and emphasizing only carbs, you very likely will not lose weight. 

The first chapter in the FAST diet book concerns the science of fasting and gives good information. Fasting tends to turn on a genetic switch for repairing genes, which have the ability to make your skin better, your GI tract more responsive, and is able to help bring down the BMI and blood pressure in people who are overweight. After fasting for more than a day with minimal or no caloric intake, the body begins to utilize stored liver glycogen for energy. After the glycogen is depleted, the fat breaks down in the liver to produce ketone bodies, not glucose, which can be used by the body and brain as an alternate source of energy. This is similar to the Atkins Diet, which advocates reduction of carbohydrates to nearly zero intake. 

Alternate-day fasting is another modality that can be used, during which the fasting days allow about 600 calories intake. On the days of eating, most people eat around 110 percent of usual trying to “catch up” on the caloric restriction from the day before. On a low-fat diet, compared to the usual American diet of lasagna, pizza, etc., the results were somewhat unexpected. The people on the high-fat diet lost more weight than the ones on the low-fat diet. This is because the low-fat diet is high in carbs, and if these are not utilized they turn to body fat. Both groups saw impressive drops in the LDL cholesterol and blood pressure. If you fast, you should make sure your food includes nutrients, vitamins, minerals, protein, carbs, and fat. Plot out what you are going to eat in a day to include all of those components. Interestingly, one breast cancer prevention study showed that reducing calories for two days a week reduces the risk of breast cancer significantly. 

The Salk Institute noted that all the time you are eating, your insulin levels are elevated and your body is “stuck” in a fat-storing mode. However, with a few hours of fasting, your body will turn off the fat-storing and turn on the fat-burning mechanism. An interesting study done at the laboratory of neuroscientists at the National Institute of Aging showed that rats that were genetically engineered on a regular diet to develop Alzheimer’s disease go twice as long without any detectable signs of dementia on a reduced caloric intake. Learning and memory as they relate to solving a problem of maze or finding food in a puzzle situation are much better when there is intermittent or even prolonged fasting. You can do a test on your own memory combined with fasting; you may find this online at cognitivefun.net/test/2.

Insulin is truly a major player in nutrition and dieting. It controls blood sugar and helps glucose go into the cells for the process of burning it for energy. For example, the brain is constantly using the energy equivalent of a 25-watt light bulb and needs a constant energy source. Insulin is stimulated by high-glycemic carbohydrates aggravated by high-glycemic load. If your cells stop responding to insulin, your blood sugar levels stay permanently high and you join the ranks of Type II diabetics, who have increased risk of heart attack, stroke, impotence, blindness, and dementia. Intermittent fasting has a remarkable effect on your standard fasting blood sugar level by lowering it as well as your LDL. 

The relation of fasting to cancer is interesting. In a paper in 2008, Valter D. Longo and colleagues showed that not only does fasting protect normal cells against chemotherapy agents, it also increases the efficiency of chemotherapy agents against a variety of cancers. There are now ongoing studies in hospitals around the world being conducted to combine intermittent fasting with chemotherapy to see what the clinical difference will be. Regarding cancer prevention, if two groups are assigned the same number of calories per week, but one group is fasting for two days a week, their fasting insulin, insulin resistance, weight, and level of C-reactive protein were down. These are measures suggesting a reduced cancer risk. Anytime a cancer cell gets less sugar to metabolize, it is going to grow more slowly and be less aggressive.

Basically these are some of the benefits of fasting: weight loss, reduction of blood glucose and insulin levels with disease risk reduction, improvement of repair genes, lowering your risk of diabetes, and overall mood enhancement with a sense of wellbeing. If you have a chance to read the FAST Diet book, you will see that there are multiple combinations of meals which can limit you to 400-500 calories, and you will see that there is actually the possibility of eating some good food on this restricted caloric intake.

If you follow the fasting techniques outlined in the book, it is important that you inform your doctor and perhaps even try to get him to do this with you if he is overweight. That way you will be able to discuss aspects of this diet with him and with others who are following it. It’s not so hard according to most people who do it and really does have great benefits if you can follow through.  

Dr. Carraway is the director of the Plastic & Cosmetic Surgery Center of EVMS. Call 757-557-0300 for more information.

James H. Carraway, M.D.

Dr. James Carraway is a full-time academic and practicing clinical plastic surgeon.  He is Director of the Cosmetic & Plastic Surgery Center of EVMS, is board certified in surgery and plastic surgery, and is a fellow of the American College of Surgeons.  Dr. Carraway has been teaching and practicing for 30+ years and has been director and chairman of residency training programs and fellowship programs in plastic surgery.
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