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Ask Rudy: Intermittent Fasting

intermittent fasting

Each day, I get a number of different questions about intermittent fasting.

Many of these questions include how intermittent fasting works and how to use it, but I also receive some other, more specific, questions and I’d like to address them here.

In this article, I’ll be answering some of the most frequently asked questions I receive regarding the popular dieting trend of intermittent fasting. 

What Is Intermittent Fasting?

Intermittent fasting is a method of dieting that is defined by going without food for extended periods of time, known as fasting, followed by a shortened or restricted time period to eat. Essentially, it’s just like the name sounds as you are intermittently spending time “fasting.”

However, there are many different methods of intermittent fasting. Here’s a list of a few:

  • 16:8
    • This method is defined by having 16 hours of fasting, followed by 8 hours of eating, completed daily. Overall, this is one of the more popular methods of fasting in the fitness world.
  • Alternate Day Fasting
    • This is a method most popular with obese individuals and in the research. This method includes alternate days of fasting for most of the day (consuming only 25% of normal calories) followed by a day of normal eating.
  • 20:4
    • This method is defined by fasting for 20 hours, followed by 4 hours of eating. This method is a bit more extreme, but many people indicate that it’s effective for them.

Overall, you can create your own method of fasting; you just need to ensure that you’re fasting for an extended period of time (over more than 12 hours), while restricting your feeding window.

Why Does Intermittent Fasting Work?

Intermittent fasting is quite effective for two reasons. The first and most important benefit is that intermittent fasting makes consuming fewer calories, easy.

Consider that you eat throughout the day, for the most part. When you spend a significant amount of time fasting, you will therefore have a decreased amount of time available to you when you can eat. Since you’ll be full for much of that time, it makes it much easier to effortlessly reduce calorie intake.

This is the number one reason why Intermittent Fasting works so well.

Second, research suggests that regularly practicing intermittent fasting can help improve insulin sensitivity. Insulin shuttles sugar from the blood into tissue, but when this process stops working efficiently, it leads to insulin resistance (1, 2, 3, 4).

This essentially means that intermittent fasting can help improve your body’s response to the food you eat, making it less likely that you’ll store it as body fat.

Which Method Of Intermittent Fasting Should I Use?

Unfortunately, giving a direct answer to this would be impossible, since everyone’s preferences and schedules are different.

However, I suggest trying methods that fit best with your routine. If you work during the day and don’t exactly need breakfast, using a 16:8 method is probably the best route to take.

However, if you need to eat earlier or have some reason you can’t fast, you might want to consider alternate day fasting.

Overall, determining the right method for your routine will really require a trial and error approach. Your best option is to start with a 12-hour fast, and increase as you see fit, until you find the perfect method for you.

Will I Lose Muscle While Fasting?

Overall, if you are consuming too few calories during the day, regardless of fasting, you run the risk of losing muscle mass. However, most people have found that fasting alone does not result in muscle loss. In fact, most research corroborates this idea.

The body actually stores sugar in a form known as glycogen. This stored form of glucose is activated when energy intake is reduced. The liver in particular, happens to be a special organ that stores the body’s last store of glycogen for situations of long-term fasting.

We see muscle loss only once liver glycogen has been depleted, as this is when the body will require additional energy.

Fortunately for all of us, research suggests that short-term reduction (less than 18 hours) probably isn’t enough to deplete liver glycogen, unless you’re very active.

Thus, there is very little possibility of losing muscle mass while fasting for fairly short durations.

Should I Take BCAAs While Fasting?

While you certainly can, you don’t need to while fasting.

If however, you’re fasting specifically to improve insulin sensitivity, I suggest avoiding BCAAs, since they elicit an insulin response. Otherwise, there’s no reason you can’t consume BCAAs, but there is also little reason that you’d absolutely need to.

As mentioned in the last point, there is very little chance of muscle loss occurring, as long as you’re consuming adequate calories. Thus, you probably don’t need to take BCAAs.

Additionally, I would suggest opting for whey, anyways. While BCAAs can stimulate protein synthesis, they can’t sustain it, like whey can.

What Can I Eat During The Fasting Period?

Overall, you shouldn’t be consuming anything of caloric value. Since fasting is defined as avoiding food, consuming just about anything would be considered “breaking the fast.”

Overall, the most commonly accepted things you can consume while fasting would be:

  1. Water
  2. Coffee/Tea
  3. Sugar Free Beverages

Anything apart from these ingredients would likely have a caloric value, which would defeat the purpose of fasting.

Lastly, as far as the coffee/tea goes, you’ll want to avoid sugar-laden options. If possible, opt for black coffee/tea. If necessary, use a sugar free sweetener such as stevia or Splenda, and opt for low calorie creamer. Overall, keep ingestion of these substances to a minimum.

Do I Need To Eat Fewer Calories While Fasting To Lose Weight?

Overall, you definitely need to consume fewer calories if you’re hoping to lose weight, regardless of the method. Just because you’re spending time fasting doesn’t mean you can override the laws of thermodynamics.

While there have been a few odd cases where people report weight loss without restricting calories, it’s likely those individuals miscalculated their calorie intake.

As it stands right now, there is no evidence to suggest that intermittent fasting will help you lose a reasonable amount of weight, unless you also reduce calories as a result of your fasting.

I’ve Heard You Need To Eat More Meals To Lose Weight, Though.

This is a longstanding myth that unfortunately continues to pervade the health and fitness industry. While most people think that more meals will “stoke the metabolism,” it unfortunately doesn’t work like that.

You have to consider that your metabolism does increase when you eat, but it does so relative to the amount of calories and types of macros you’re consuming. For instance, your metabolism will rise a bit more for protein than it will carbohydrate.

However, over the long term, there will be very little difference.

Further, it’s also likely that increasing meal frequency will actually make you hungrier. Ghrelin, the hunger hormone, is released following a rhythm of when you normally eat. If you eat 8 times a day, you can expect ghrelin to be released much more often, which will mean you’re hungry more often (5).

Overall, there is no reason to say that 6 meals will be better for fat loss than 3. The International Society for Sports Nutrition has, in fact, arrived at the same conclusion (6).

Can I Eat Whatever I Want While Using Intermittent Fasting?

Since your window of eating opportunity is smaller, you can certainly get away with consuming foods, which would typically be considered as unhealthy; however you’ll still need to manipulate your calorie intake if you want to change.

Additionally, eating junk food constantly can make hitting your macro requirements difficult or even impossible.

Overall, I suggest sticking with the 80/20 rule if you’re serious about making a change. This simply means eating low calorie-dense, high protein meals 80% of the time, while allowing for other food options, 20% of the time.

This will ensure that you get to enjoy yourself, but you’re doing it in a controlled way, while ensuring that, for the most part, you’re getting the nutrition you need.

intermittent fasting

Does Intermittent Fasting Work Better Than Other Diets?

Overall, this is very subjective.

If intermittent fasting helps you better manage your calorie intake throughout the day, then this method of dieting may in fact be a more effective approach than other styles.

Just keep in mind that, for the most part, there is no magic diet option, but rather there are different styles of diets each with different properties. You may find that IF is a style with properties that other styles do not have and its properties help you succeed.

While I’m a big fan of intermittent fasting, it’s certainly not the only method of dieting that I promote. My advice is to find the method that helps you make a change with the least effort possible.

Ask Rudy: Intermittent Fasting

Since intermittent fasting is so popular, I wanted to ensure that I could answer at least some of the most frequent and important questions regarding the diet.

If you happen to have additional questions regarding intermittent fasting, please comment in the private Facebook group. If the question is common and sufficiently interesting for others, I might even feature it in a future update! 


  1. Trapp, E. G., Chisholm, D. J., Freund, J., & Boutcher, S. H. (2008). The effects of high-intensity intermittent exercise training on fat loss and fasting insulin levels of young women. International journal of obesity, 32(4), 68Halberg, N., Henriksen, M., Söderhamn,
  2. Mattson, M. P., & Wan, R. (2005). Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems. The Journal of nutritional biochemistry, 16(3), 129-137.
  3. N., Stallknecht, B., Ploug, T., Schjerling, P., & Dela, F. (2005). Effect of intermittent fasting and refeeding on insulin action in healthy men. Journal of Applied Physiology, 99(6), 2128-2136.4-691.
  4. Halberg, N., Henriksen, M., Söderhamn, N., Stallknecht, B., Ploug, T., Schjerling, P., & Dela, F. (2005). Effect of intermittent fasting and refeeding on insulin action in healthy men. Journal of Applied Physiology, 99(6), 2128-2136.
  5. Lesauter, J., Hoque, N., Weintraub, M., Pfaff, D. W., & Silver, R. (2009). Stomach ghrelin-secreting cells as food-entrainable circadian clocks. Proceedings of the National Academy of Sciences, 106(32), 13582-13587. doi:10.1073/pnas.0906426106
  6. La Bounty, P. M., Campbell, B. I., Wilson, J., Galvan, E., Berardi, J., Kleiner, S. M., … & Smith, A. (2011). International Society of Sports Nutrition position stand: meal frequency. Journal of the International Society of Sports Nutrition, 8(1), 4.


About the author

Rudy Mawer, MSc, CISSN

Rudy has a 1st class BSc in Exercise, Nutrition & Health and a Masters in Exercise & Nutrition Science from the University of Tampa. Rudy currently works as a Human Performance Researcher, Sports Nutritionist and Physique Coach. Over 7 years he has helped over 500 people around the world achieve long last physique transformations.

He now works closely with a variety of professional athletes and teams, including the NBA, USA Athletics, World Triathlon Gold Medalists, Hollywood Celebrities and IFBB Pro Bodybuilders. If you would like to get in contact or work with Rudy please contact him on social media.

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