Fitness in Fasting: I Tried 5 Different Intermittent Fasting Protocols for Workout Performance

As someone who has been training for over 17 years, I’m a sucker for new fitness protocols. Over the years, I’ve tried numerous diet and training protocols to gain an edge and improve my overall health and well-being.

Intermittent fasting (IF) is hands down one of the most effective weight loss diets I have ever tried. I was initially skeptical about IF, but I knew I had to try it as soon as I discovered that four-time Fittest Man on Earth®, Rich Froning, follows this diet.

IF involves alternating between periods of voluntary fasting and eating. There are multiple IF protocols you can choose from, depending on your experience level and goals.

Recently, I took on one of the longest fitness challenges I have ever done. I tried five different intermittent fasting protocols for four weeks each to ascertain their impact on my workout performance, body composition, energy levels, and strength.

In this article, I share the results of this five-month-long challenge and reveal the most effective IF diet for boosting training performance. I also discuss ways to balance fasting and exercise timing and how you can get the best bang for your buck. We have a lot to unpack, so sit tight and read on.

My 5-Protocol Intermittent Fasting Experiment

Here are the five IF protocols I tried over five months and my experiences with them:

1. 16/8 Method

This is the most popular (and beginner-friendly) intermittent fasting protocol. It involves fasting for 16 hours and eating in an eight-hour window. Most people adhere to this method by skipping breakfast and eating normally for the rest of the day.

Although I had previous IF experience, I decided to begin my five-month challenge with this method to give my body time to adjust. I felt my metabolism switching gears in the first week itself as I skipped breakfast.

Notably, I didn’t limit my calorie intake and kept it to around 3,000 calories to ensure I didn’t lose muscle tissue or strength during the first phase of this challenge.

As expected, my workout performance (strength, endurance, and recovery) was pretty standard during the four weeks of the 16/8 method. However, I did notice a reduction in my body fat percentage in the final week as my body adapted to using stored body fat for energy.

2. 5:2 Diet

In the 5:2 method, you eat normally five days each week and restrict your calorie intake to 500 to 600 calories on two non-consecutive days. While this protocol is more flexible than the 16/8 method in that you only have to restrict your diet for two days, limiting yourself to 600 calories on two days is a big challenge.

I was pretty anxious going into this diet as I’m not a fan of full-day fasting. However, the allowed 600 calories during the fasting days were a big relief — or so I thought.

To put things into perspective, a 500 to 600-calorie for someone trying to build or maintain muscle is a joke. I’ll give you an example.

Greek Yogurt Parfait with Berries and Nuts (approx. 600 calories)

• Plain Greek yogurt (2 cups) — 300 calories, 48g protein
• Mixed berries (1 cup) — 60 calories, 1g protein
• Granola (¼ cup) — 120 calories, 3g protein
• Chopped nuts (¼ cup) — 120 calories, 6g protein

Any bodybuilding enthusiast could tell you a snack like this gets digested within half an hour.

We now come to the fun part — my workout performance.

All my training parameters, including strength, endurance, and stamina, took a big hit as soon as I switched to the 5:2 IF method. My recovery times also were at an all-time low. My most immediate instinct was to reprogram my workouts to preserve muscle mass.

I switched from a six-day-a-week training routine to five days. I also aligned the fasting days with the rest days to avoid overexertion.

The muscle mass loss at the end of the four weeks wasn’t as bad as I had initially thought, probably because the fast was restricted to two days a week. On the bright side, my muscle conditioning improved significantly compared to the 16/8 phase, thanks to the substantially lower calorie intake.

3. Eat-Stop-Eat

The eat-stop-eat (ESE) protocol is a variation of the 5:2 diet. The ESE method involves a 24-hour fast once or twice a week. It might sound very intensive, but some believe it is more manageable and effective than the 5:2 method if done systematically.

Contrary to popular opinion, even with this IF method, you still eat something daily.

For instance, if your fast lasts from 9 a.m. on a Tuesday to 9 a.m. on a Wednesday, you will have a hearty meal before starting the fast on Tuesday and a healthy meal after ending the fast.

My fasting and training approach and results remained pretty much the same from the previous month, and I saw no significant changes in my physique metrics, daily energy level, or workout performance.

4. Alternate-Day Fasting

As the name suggests, it involves alternating between days of normal eating and complete (or severely restrictive) fasting. This protocol is a big jump from the eat-stop-eat method and should be reserved for experienced fasters. That said, you can consume up to 500 calories on fasting days in this diet.

Although my body had adjusted to the longer fasts, the alternate-day fasting protocol didn’t make things easier. Fasting twice a week on non-consecutive days is very different from fasting every alternate day; no amount of eat-stop-eat and 5:2 dieting can prepare you for it.

My metabolism ramped up considerably during this phase, and I was consistently hungry throughout the fourth month of this challenge. I must mention that I felt incredibly energized after my first meal on the normal eating days during the month.

I didn’t make any changes to my training routine during this phase. In hindsight, I think it was a mistake. I started feeling the burden of this routine toward the end of the 16th week.

All my workout performance markers dipped during the alternate-day fasting protocol. My energy levels were down, my endurance and recovery were significantly poorer, and I couldn’t lift as heavy as I could in the previous three phases.

That said, I lost four pounds (1.8 kilograms) during the alternate-day fasting phase, and my muscle separation improved drastically.

5. Warrior Diet

This is one of the extreme forms of IF. It comprises alternating between 20 hours of undereating (mainly raw fruits and vegetables) during the day and eating one large meal in a four-hour window, typically dinner. Furthermore, you must only eat whole, unprocessed foods, similar to what ancient warriors might have eaten during a hunt.

I suggest beginners stay away from the warrior diet to avoid any nutrient deficiencies.

After the experience with the alternate-day fasts and the restrictive nature of the warrior diet, I knew I had to make changes to my workout programming. I reduced my workout frequency from five days a week to three days.

Since my biggest objective during this experiment was not to lose muscle tissue, I tried to conserve as much energy as possible. I practically went through the final month in power-saving mode. This tells you volumes about my recovery abilities during this phase.

It was also the only phase during this challenge where I didn’t feel like working out since I was so low on energy. Not only were my energy and endurance levels declining, but I also lost five pounds (2.2 kilograms) during this phase. This was when I ate around 2,000 calories in a single meal.

Honestly, of all the IF dieting protocols, this one felt like a fad to me. I mean one meal a day is brutal enough, so why do you have to restrict yourself to ancient-style foods?

To maximize your overall health and well-being, you must hit your daily micro and macronutrient goals through nutrient-dense foods. Sticking to a particular variety of foods makes no sense to me.

The Interplay of Fasting and Exercise Timing

Fasting and fed workouts can both have a place in your workouts. Here is what I recommend:

Fasted Workout

Your body is in a fat-burning state while you are fasting. Fasted workouts can enhance fat oxidation and boost your body’s ability to use fat as fuel. That said, you must maintain a daily calorie deficit to maximize fat and weight loss.

Fed Workout

The biggest problem with fasted workouts is that it makes people feel they have no gas in the tank. Conversely, when you exercise after eating, you have ample glycogen stores to power explosive movement and sustain long sessions. Most people believe that fed workouts can improve performance, especially in strength or high-intensity training bouts.

That said, eating too close to a workout can lead to digestive discomfort. I recommend eating one to two hours before a workout. It ensures optimal digestion and delivery of essential nutrients to every muscle in the body.

Understanding Intermittent Fasting

Intermittent fasting is a versatile and flexible dieting protocol that can be modified to suit an individual’s specific needs. It has risen in popularity and become one of the most popular diets of all time due to its various benefits, including weight loss, improved heart health, reduced risk of diabetes, improved cognitive function and sleep, and reduced inflammation. (1)

So, how does IF work?

When you don’t eat for an extended period, your body switches its primary fuel source from glycogen (from carbs) to stored body fat. This can boost metabolism, helping burn more calories throughout the day.

Fasting can also influence hormone production. For example, IF boosts insulin sensitivity, which can regulate blood sugar levels and growth hormone production to maximize muscle and strength gains and maintenance.

IF also triggers a cellular process called autophagy, which is a natural process involving removing unnecessary or dysfunctional cell components so your body can operate more efficiently.

That said, IF comes in all shapes and sizes, and you must pick the one that suits your lifestyle, and you can stick to in the long term.

Potential Risks and Drawbacks of Intermittent Fasting

Make no mistake, as awesome as IF is, it has its setbacks. Here are a few you should know about:

• Nutrient Deficiencies: A poorly structured IF protocol can result in nutrient deficits that can lead to chronic health issues.
• Dehydration: Not eating for extended periods can cause electrolyte imbalances, increasing the risk of dehydration.
• Side Effects: Headaches, chronic fatigue, irritability, and difficulty concentrating are common side effects of IF, especially in the initial stages.

Like any fitness regime, intermittent fasting demands consistency, dedication, and discipline for optimal results. Remember, no two people will respond to a particular IF protocol in the same way.

Try different IF methods and monitor the results to determine what works best for you. Plus, learn to listen to your body to minimize the risk of side effects.

People dealing with existing health conditions should get their doctor’s clearance before starting intermittent fasting or any other health and fitness protocol.

Conclusion

Intermittent fasting can help torch fat, boost energy, and even improve longevity. My five-month-long experiment proves that an individual can sustain their workout performance while intermittent fasting. However, choose a protocol that is too stringent, and it will certainly hinder your work capacity.

People aiming for hypertrophy and optimal workout performance will be best off sticking with a conventional meal plan comprising three to six meals a day. While you could manage these results with a 16/8 IF method, it will require meticulous planning and execution.

If you have any questions about the IF protocols or need help implementing them into your routine, post them in the comments section below, and I’ll be happy to help!

References:

1. Reddy, B. L., Reddy, V. S., & Saier, M. H., Jr (2024). Health Benefits of Intermittent Fasting. Microbial physiology, 34(1), 142–152. https://doi.org/10.1159/000540068

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