Fasting 101 – What you need to know

The fitness industry frequently goes through trends. It seems that one of the latest, most popular trends in the industry is fasting. Although it seems to have become popular fairly recently, fasting has been around for thousands, even millions of years, going all the back to the way the first humans ate.  The first humans would go for prolonged periods without eating, having to wait until making a kill before eating as much as they could over a short period of time before the meat would spoil. A more modern is example is looking at the way large carnivores such as lions or wolves eat, as these animals go for days without eating until they make a kill and eat as much as possible, then going for days again without eating. Many animals including humans have evolved this way and produced a survival mechanism where the body produces certain hormones and increased energy boosts during times of low food allowing for a greater a chance of survival (Mattson and Wan, 2005).

It has only been recently within the last few thousand years that food has been readily available where humans do not have to go out and hunt, or gather food to eat.

Not eating for extended periods is very similar to the validity behind fasting.  Fasting is where you do not eat for prolonged periods allowing your body to tap into fat stores as opposed to using stored food in the form of glycogen for energy.

This shatters the “bodybuilding” paradigm where you have to eat every 2-3 hours or you will go catabolic and start losing muscle. This bodybuilding approach is 100% completely false.  Muscle is much harder to lose than you think. As long as you are still providing stimulus to the muscles through weight training and eating adequate protein (0.6-0.8 g/lb), your body will primarily use body fat until your fat stores are extremely low. Your body wants to preserve as much muscle as possible so it is not until your body enters the late stages of starvation that it will start to burn muscle.

If you’ve also heard eating every 2-3 hours speeds up your metabolism, this also completely false, whether you eat all your calories in one or two huge meals or spread out over 10 meals, it does not matter, it comes down to calories in versus calories out (calories burned). Simply put, if you eat more calories than you burn, you will gain weight, if you eat less calories than you are burning, you lose weight. Sure, some may argue that absorption of food is greater when spread throughout the day but the scientific validity behind this is vague. You are splitting hairs, what much more important is your calories in vs. calories out, it does not matter how many meals you eat per day.

So what does this mean about fasting? Fasting works by fueling the body by using stored body fat as the primary source of fuel when you have not eaten for extended periods.

Fasting Benefits

If you’ve heard about intermittent fasting, you’ve probably heard about the associated benefits that go along with it. Benefits include greater ability to burn fat while in a fast, improved cognitive function, lower cholesterol levels, increased insulin sensitivity, improved metabolic rate, lower blood pressure, reduced cellular oxidative stress, increased growth hormone production and decreased inflammation all leading to the possibility of a longer life span (Mattson and Wan, 2005, Ho et al. 1988).

Of these benefits, a few jump out at me as a major reason to try fasting for myself. Decreased inflammation is something I am always looking for living with Crohn’s Disease. Not eating for prolonged periods makes sense as it gives the digestive tract time to heal without having more food pushed through it. The other major benefit is the release of growth hormone while in a fast. Growth hormone in humans stimulates growth, cell regeneration and cell reproduction which makes it a major factor in recovery and muscle growth as well as destruction of damaged immune cells which is invaluable in autoimmune diseases. It is a naturally produced hormone but may also be artificially administered to the body as a performance enhancing drug. The natural release of growth hormone is perfectly safe and extremely beneficial to your body by increasing energy and muscle growth. As a natural athlete I am always looking for ways to optimize my results and increase performance in the gym and am always interested in ways such as fasting and weight training as a way to increase the natural release of growth hormone.


How to Fast Safely

There is a right way and a wrong way to do just about anything, fasting included. Fasting does not mean you are skipping meals or not eating because your excuse is that you’re fasting. Your body requires adequate nutrients whether you are eating them spread out over 16 hours or compressed into 4 hours. Depending on your goal you should know what your body needs nutritionally before you even think of fasting. Know what you should be feeding your body. Fasting safely and effectively requires you to eat the same calories and macronutrients you need, just in a shorter period of feeding than if you were to eat throughout the day. For example, if you need 2500 calories and your breakdown is 150g protein, 275g carbs and 89g of fat you need to fit all of those calories in once you break the fast. If you prefer eating two meals of 1250 calories or 4 smaller meals of 625 calories each, find out what works best for you.

When fasting, one major thing to remember is you do not want to break your fast by consuming calories during the fast through something you eat or drink. You may drink zero calorie beverages while fasted such as water or black coffee. Water or carbonated water is a good thing to consume while fasted as it keeps you full and reduces hunger.

There are several other versions of intermittent fasting with some being more extreme or efficient than others but find one that works for you.

The 16/8 Method

This is the most popular and easiest way to utilize fasting. The 16/8 method is 16 hours of fasting and 8 hours of feeding. The easiest way to do this is eat dinner the night before and do not eat anything until lunch the next day. You are not eating as you’re sleeping so overnight counts towards your fast and if you skip breakfast or have a later breakfast, the 16h fast is relatively easy to do. For example, if you eat dinner at 7 PM you would not eat again until 11 AM. The real benefits of fasting do not kick in until the 16 hour mark. This method is ideal for someone who has trouble eating first thing in the morning.

The 24h Method

This method is slightly more difficult but still do-able. This method is where you do not eat for an entire 24h period. For example, eating dinner and not eating anything until dinner the next day. This method is best suited to people who have busy jobs or schedules and cannot eat during the day. The difficulty of this method is you must eat one large meal over a short period before going to sleep. Fitting adequate food in this short amount of time is difficult for many. This method is only recommended 1-2 times per week where you go back to eating normally on the days you are not fasting.

Applicable to all fasting methods is weight training and cardio while fasted. Yes, you can train while fasted and not lose any muscle. This is the basis behind fasted cardio. I’m sure almost everyone has heard about doing fasted cardio and this is the basis behind it. Doing cardio and weight training while fasted forces the body to tap into alternative energy sources other than food as you have not eaten for an extended period. Training while fasted is definitely something to get used to but it makes fasting much more effective as the body must tap into fat stores for energy.

The two main ways I could see someone fasting wrong is not eating enough/the right nutrients or binging out which is justified by the fast. First, it may be hard for some people to eat 2500 calories within a short window. Feeding your body what is needs is absolutely essential for recovery, performance, energy levels and overall health. Skipping meals or not feeding the body what it needs is where fasting can be done improperly. Secondly, the other problem that can occur is binging out on the wrong foods just because it can be justified by the fast. If you’re fasting to convince yourself that eating unhealthy foods is okay because you fasted that day creates an unhealthy relationship with food. This is the wrong way to do fasting. Once in a while it may be effective to use fasting after falling off of eating the right foods for a few days but fasting should not utilized to justify eating unhealthy.


Fasting in a Caloric Surplus or Deficit?

Fasting is most often used as a tool to reduce body fat quicker than conventional dieting. To utilize the full effectiveness of fasting is to eat in a caloric deficit. If you are eating a lower carb diet while in a deficit this may speed up fat loss as your glycogen stores are already low.

Fasting can also be done while in a caloric surplus when trying to gain muscle. The effectiveness of fasting may not be as pronounced as in a deficit because glycogen stores will already be full from the surplus of calories and carbs but fasting may be used as an effective tool to stay lean while in a “bulk”. The only problem I can see with this is the amount of food you have to eat while in a surplus. The amount of food required to put your body into a caloric surplus is usually a lot and fitting all that food into a short feeding window may be difficult for some.

What might be a better option is to utilize fasting for 3 consecutive days a week while eating in a small deficit during these days then continue with your surplus the rest of the week. This will give your body time to deplete glycogen stores and tap into body fat for energy. Another way to utilize fasting is to do a short “mini-cut” to keep body fat low. I previously mentioned this in Offseason Nutrition Guide and Tips, utilizing mini for a few weeks by eating in a caloric deficit to keep unnecessary body fat levels down while in a phase of muscle gain. Using fasting in this mini cut will show the best results as opposed to using it while trying to eat in a surplus.

The bottom line here is fasting while eating in a caloric surplus is more difficult and can be done but it will not be as effective as eating in a caloric deficit.

Is fasting right for you?

Fasting definitely is not for everyone. I do a lot of experimenting in the offseason with my nutrition, workouts and performance. I am always looking for ways to optimize mental and physical performance and I wanted to try fasting out for myself. I’ve always known I do not fare well without food since I was young but I figured I would give it a solid try. I did a 16 hour, 18 hour and 22 hour fast spread out over a few weeks. The 16h fast was by far the easiest with no real issue but as I pushed the fast longer over the next few weeks, each time I ended up getting nauseous, hangry and light headed. My workouts suffered and were not as good as when I have eaten prior to lifting.

Another difficulty I face with fasting is the amount of food I have to eat after the fast. If I’ve done a 22 hour fast I may only have a short window to fit in all the calories I need before going to sleep. Having Crohn’s, I’ve always found that smaller, more frequent meals is easier on my digestive system than eating a few larger meals throughout the day. Pushing 2500 calories through my intestines in a short amount of time is very hard on my digestive tract and is a recipe for disaster if there is any inflammation present. The bottom line is fasting is just not for me. My biggest tip is that everyone should experiment with nutrition and find what works best for you. If you’re someone who has a hard time eating first thing in the morning or you work a job that is difficult to eat at then maybe fasting could be for you. Be in-tune with your body and listen to the signals it is giving you. If fasting works for you, by all means do it.

Ho KY, Veldhuis JD, Johnson ML, Furlanetto R, Evans WS, Alberti KG, Thorner MO. 1988. Fasting enhances growth hormone secretion and amplifies the complex rhythms of growth hormone secretion in man. Journal of Clinical Investigation J. Clin. Invest. 81:968–975.
Lieberman HR, Caruso CM, Niro PJ, Adam GE, Kellogg MD, Nindl BC, Kramer FM. 2008. A double-blind, placebo-controlled test of 2 d of calorie deprivation: effects on cognition, activity, sleep and interstitial glucose concentration. American J Clin Nutr. 88(3):667-76.
Mattson M, Wan R. 2005. Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems. The Journal of Nutritional Biochemistry 16:129–137.
Soeters MR, Lammers NM, Dubbelhuis PF, Ackermans M, Jonkers-Schuitema CF, Fliers E, Sauerwein HP, Aerts JM, Serlie MJ. 2009. Intermittent fasting does not affect whole-body glucose, lipid, or protein metabolism. American Journal of Clinical Nutrition 90:1244–1251.

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