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If “Starvation Mode” is real, why do we recommend fasting?

by | health and fitness, obesity | 0 comments

IMAG1260_2In my last post, I discuss the body’s adaptation to a consistent, strenuous exercise program in conjunction with a low-calorie diet over the course of time. The body adapts to this stimuli by slowing down the metabolism in an effort to preserve energy. It will work as hard as possible to store fat, even if the body maintains muscle from a consistent exercise program. According to the study that researchers did on the contestants of The Biggest Loser, the metabolism slowed down by 356 to 399 calories a day after six weeks (according to Jason Fung, the metabolic rate slowed down approximately 789 calories a day. I could not find that number in the study itself, but it would not surprise me if it did). Since muscle was maintained, the logical conclusion for the slower metabolic rate was due to hormonal shifts in the body. In essence, the body’s set point was adjusted downward. Additionally, the researchers (and many others not involved on this project) say that once the metabolism slows down from an extreme diet and exercise program, it is a more or less permanent condition. The individual will have to keep up the extreme diet and exercise program just to keep off the weight. Is it any wonder that most people do not stick to a diet and exercise program, knowing that he or she will have to exercise excessively and eat like a bird. Being hungry and tired all the time does not sound like a fun life, and I do not blame them.

So Why Do We Recommend Fasting?

It did not dawn on me when I was writing the last blog about adaptive thermogenesis (starvation mode) that we recommend to our clients a fasting protocol as part of the nutrition program. It was brought to my attention by my client after she read my blog post. She initially thought the blog would talk about the importance if fasting, but I instead wrote about how chronic under eating (and chronic exercise) made fat loss harder. This, of course, was confusing to her so we had a discussion about the differences between fasting and chronic under eating. Moreover, it made me realize that I had to clarify the difference to you, dear readers as well. Hence the writing of this blog post.

Fasting Has a Different Hormonal Response 

To recap one of the points I made in my previous blog about starvation mode, the main challenge of losing body fat is high insulin levels. When insulin levels are high, the body will store fat. It kind of locks the fat in the fat cells, making it very difficult for the body to use it for energy. The advice given by most fitness professionals and nutritionists to eat small, frequent meals during the day, along with carbohydrate rich foods make it very hard for the body to use fat for fuel, even on a low-calorie diet.

Fasting, on the other hand, has a completely different effect on the body. First of all, insulin levels do drop. All foods raise insulin levels. Some more than others. For example, refined carbohydrates raise insulin levels the most and fatty foods will raise it the least…but fatty foods will still raise insulin. When we are in a fasted state, the opposite happens. Insulin goes down, thus the body is more capable of tapping into fat stores for fuel†.

Another benefit of fasting that contrasts a chronic calorie restriction protocol is an increase in adrenaline†. Adrenaline releases stored glycogen and facilitates fat burning, even if blood sugar is high. Furthermore, higher adrenaline levels actually increase metabolism. Research shows that fasting for four days increased energy expenditure by 12 percent. Most people, when they fast, will actually feel revitalized and energetic, and I am no exception to that. I rarely eat breakfast or lunch anymore, and when I do eat lunch, I feel more lethargic and a bit out of sorts. I just want to mellow out for the rest of the day. On the other hand, when I forgo breakfast and lunch I stay motivated and highly energized. I guarantee you that chronic, consistent calorie restriction does not do that.

Growth hormone also goes up while fasting†. Imagine that. Body builders are notorious for using steroids and exogenous human growth hormone to build the inhuman amount of muscle that they do. They clearly understand the benefits of growth hormone. On the flip side, we all produce less human growth hormone as we age, and researchers believe that low levels of human growth hormone is a major cause of aging. Thus, we must do everything we can in a healthy and holistic manner to maintain high human growth hormone out put, and it looks like fasting is a tool in the tool box that can do that.

Growth hormone, released in conjunction with both cortisol and adrenaline, which happens while fasting, sends a signal to the body to increase the availability of glucose for use as fuel. As this is going on, growth hormone will also increase the body’s ability to use fat for fuel by raising levels of an enzyme called lipoprotein lipase. Lipoprotein lipase releases fat from the fat cells for fuel†. So the body will use both fat and glucose for fuel at the same time.

This brings up a point that was brought to my attention by Dr. McGruff in his book Body by Science (Pg. 207), and that is insulin is the “trump hormone”. What he means by this is that when insulin levels are high, all of the fat burning and muscle-building (and maybe even anti-aging hormones) are suppressed. This is a necessary response because glucose is very toxic to the body and it has to be tightly regulated. So in response to high glucose, the body will increase insulin first and foremost. It has to handle the emergency first, and then it could get back to fat burning and muscle building.


The body has a very different response to fasting than it does to a regimen of low-calorie eating coupled with a chronic consistent exercise program. The body will go into “starvation mode”, better known as adaptive thermogenesis on a consistent low calorie diet and exercise program. It will lower its metabolic rate, and it would do it to a significant degree. It will do this in an attempt to simply survive. Applying this approach to lose weight can be a frustrating and punishing ordeal. Fasting, on the other hand, will actually increase the metabolism and help keep you energized throughout the day. Moreover, fasting helps the body tap into the fat stores at the same time that it will use glucose for fuel. And finally, fasting can play an important role in building and maintaining muscle…and slowing down the aging process. There are indeed many good benefits to fasting. In a later post I will give a few good examples of fasting that you can incorporate into your nutrition program.


Gregg Hoffman

† These points are from the book The Complete Guide to Fasting: Heal Your body Through Intermittent, Alternate-Day, and Extended Fasting written by Jason Fung. Jason Fung is a doctor in Canada who has a very succesful practice helping his diabetic clients back to health through diet and a holistic lifestyle. I find his writings very insightful, and it has helped me with my business. You can learn more about him Here.