Intense Exercise Training During a Juice Fast? Is This Even Possible?

Written by Nina Cherie Franklin

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Juice Fast

Fasting with fresh vegetable and fruit juices is an excellent method of detoxification or a way of introducing a comprehensive lifestyle change (i.e. diet modification, exercise training, weight loss). What is cool about juice fasting is that you reap the benefits of a rested digestive system without depriving your body of essential vitamins, minerals, and naturally-occurring phytonutrient compounds found in plants which promote good health.

About seven years ago, I partook in a 21-day juice fast just prior to converting to vegetarianism (I’ve since reintroduced poultry and seafood into my diet). Leading up to this fast, I had abandoned a high-intensity bodybuilding resistance training program that required me to consume large quantities of red meat and protein products and I just felt toxic. Furthermore, once I discontinued my high-intensity resistance training program and opted for a more moderate one, I found myself holding on to about 25 extra pounds of unsightly fat. The intention of my going on a 21-day fast was not to lose weight, but to initiate a physiological “reset” and cleanse myself of the toxic byproducts associated with years of consuming meat. However, I lost 35 pounds during this juice fast and physiologically I felt great. When I reintroduced solid foods into my diet, I ultimately regained about 10 pounds which I totally expected due to metabolic adjustments.

This brings me to the present. About two weeks ago, I initiated a 7-day juice fast while continuing my 60 to 90 minute morning cardiovascular routine with a twist on Day 1. I had registered for an indoor cycling certification months prior to my fast and refused to postpone it. As a result, the first six hours of Day 1 were spent in an overly cooled health club--two hours of which were spent exercising on a Spinning bike. Lucky for me, I had 16 ounces of fresh juice in hand which I consumed gradually with a whole lot of water. Sounds like hell but after completion of this day, I felt invigorated.

I decided to try and maintain my weekly resistance training routine which consists of 4 days of moderate- to high-intensity weightlifting, but I was quite skeptical. In fact, I dreaded the idea of teaching my 6:30pm power weightlifting class on Day 2. Nevertheless, I dragged myself to the health club in preparation for a pitiful workout as I had throbbing hunger pangs. However, something happened to me after I took my class through a 3rd set of squats...I felt more energized than I’ve ever been on a fast and sweated a river as I underwent a full hour of power weightlifting. Most surprising to me was the fact that I was not hungry afterwards. Feeling completely inspired by this physiological response, I decided to continue lifting weights for the duration of the fast. My energy never subsided and the hunger pangs never returned.

My strategy for countering hunger throughout the 7-day period involved drinking 16 to 40 ounces of fresh juice a day in 4 to 8 ounce servings in order to trick my body into satiety. The juice blends varied from green leafy and cruciferous vegetable combinations to those rich in beta-carotene including broccoli, spinach, romaine, green/red/yellow pepper, tomato, and carrot. For added flavor, I included fresh fruit juices into my blends including, apple, pear, plum, mango, orange, strawberry, and grape.

I have a theory as to what happened to me while engaging in intense exercise during this juice fast. The typical response to any fast involves a decrease in metabolism with the purpose of conserving energy. In addition, both fat and muscle breakdown occurs with concomitant loss of water. These responses are most dramatic with prolonged fasting (i.e. greater than 10 days) but can begin as early as 3 days after. Such responses can make one feel sluggish and de-energized. However, it is possible that the dramatic increase in metabolism that occurs during and after weightlifting, and exercise in general, could counter dramatic decreases in metabolism. Furthermore, because the preservation of muscle that occurs with resistance training can inhibit the breakdown of muscle that normally occurs during a fast, the rate of metabolism could be maintained.

This theory may explain why my physiological responses to the juice fast were not typical. I felt refreshed, invigorated and energized from the first day of cycling exercise, to the second day of weightlifting, and on all subsequent workout bouts. In addition, I lost 9 pounds during the 7-day period, and kept off 7 upon consumption of solid foods, which is evidence that 1) there was not a significant decline in my metabolic rate, and 2) the majority of this weight loss was fat.

So what? Well, I’m not telling you to start a juice fast while engaging in a 2-hour daily workout routine for the purpose of weight loss. I am just letting you know that it is possible to combine intense exercise training with juice fasting and if you are physically able to do so, it may be the best way to use fasting for weight loss. However, I do not recommend that juice fasting be used for weight loss unless done under supervision from a trained professional such as a naturopath in conjunction with a qualified exercise physiologist or fitness specialist. On another note, if a weight loss program of juice fasting and exercise training is not a precursor to a comprehensive lifestyle change, and the intention is to binge eat afterwards or use food as a reward to celebrate a weight loss accomplishment, consider another program. Remember, If caloric intake exceeds caloric expenditure ANYTIME after stopping such a weight loss program, weight gain will ensue.

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Nutrition