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How to lose fat faster (and keep your muscles) with cardio training while fasting Part 2

Wie Du mit Cardiotraining im Fastenzustand schneller Fett verlierst (und Deine Muskeln behältst) Teil 2

After defining what exactly is meant by (cardio) training in a fasted state and why this type of training can accelerate fat loss in the first part of this article, in this second part of this article I will discuss how you can not only lose more fat through HIIT training in a fasted state, but also protect your muscles more effectively from diet-induced muscle loss. I will then go into more detail about planning your diet and supplements before showing you how to put what you have learned into practice using a specific example plan.

You will also lose less muscle

If you are dieting to lose fat, then your primary goal after the actual fat loss should be to maintain your existing muscle mass. And when it comes to muscle maintenance, cardio training at a constant intensity has a pretty bad reputation.

There are good reasons for this. Scientific studies show, for example, that the longer a cardio training session lasts, the more it impairs muscle strength and growth. However, that doesn't mean you have to fear cardio. There are some simple steps you can take to maximize your fat loss while minimizing potential muscle loss:

  1. Use a moderately aggressive calorie deficit.
  2. Eat a high protein diet.
  3. Perform 3 to 5 resistance training sessions per week.
  4. Keep your cardio training to a minimum.

The reason for point number 4 is this:

If you're in a calorie deficit, the less cardio you do, the more muscle you'll maintain.

This may sound a little oversimplified, but it works quite well as a rule of thumb. You could, of course, do no cardio at all, but you probably won't achieve what you want. If you really want to get lean (under 10% body fat for men and under 20% for women), then there is a point at which you need to include cardio in your program. You will need this cardio training simply to keep your energy expenditure high enough to keep losing fat.

Therefore, you will find yourself in the following dilemma: You need cardio training to increase your energy expenditure and burn fat, but you also need to keep this training in the minimum range to maintain your existing muscle mass.

So what can you do? What you shouldn't do is what most people do: hours upon hours of grueling cardio training per week that burns both fat and muscle. Combine this with a very low calorie diet, which is also very common, and you have the perfect storm for misery and muscle loss.

Get the best of both worlds with high-intensity interval training

You don't need to invest more than a few hours a week to see visible fat loss... and no training session needs to last longer than 20 or 30 minutes.

How to use HIIT correctly

Thinking about incorporating HIIT into your fat loss program? Excellent. However, you will probably still have a few questions such as...

  • How intense should the high-intensity intervals be?
  • How long and how easy should the rest intervals be?
  • How long should the training sessions be?
  • How often should HIIT training sessions be performed?

A comprehensive treatment of all aspects of HIIT would of course go far beyond the scope of this article. However, a quick search in the blog under the keyword "HIIT" will provide you with more than enough articles on the subject.

Supplements that can make cardio training more effective when fasting

Supplements are not the key to fat loss, but they can help you accelerate your progress. To maximize fat burning and better protect muscles from breakdown during a diet, I like to use the following:


Millions of people can't get going in the morning without their coffee, but caffeine can do a lot more than just wake you up. Caffeine can:

  • Help you lose fat by increasing the amount of energy your body burns throughout the day (13).
  • Increase your strength, muscle endurance and anaerobic capacity, helping you to have productive workouts even when dieting (14, 15, 16).


As we have already seen, potential muscle loss is one of the biggest disadvantages of cardio training in a fasted state. The most common solution to this problem is the use of BCAAs. BCAAs can help, but a molecule called β-hydroxy β-methylbutyrate (HMB for short) is even better for this.

HMB is formed naturally in your body when it metabolizes leucine. Although HMB is often touted as a supplement to support muscle building, the studies on this topic are mixed.

However, there is one benefit of HMB that is well scientifically proven: HMB is a very effective anti-catabolic agent (17). In other words, HMB is very good at preventing muscle breakdown, which means you'll recover faster from your workouts and experience less muscle soreness. In addition to this, unlike BCAAs, HMB has no effect on insulin levels and therefore will not interrupt your fasting state (18).

All of these things make HMB a very effective supplement to support the benefits of training in a fasted state. Its powerful anti-catabolic effects will allow you to benefit from the full fat loss benefits of training in a fasted state without the problems associated with insulin spikes.

It is also worth noting that HMB is more effective than the amino acid leucine, from which HMB is formed, in terms of its anti-catabolic, muscle loss preventing effects (19). This means that HMB is more effective than BCAA supplements, which rely primarily on the anti-catabolic effect of leucine, as the other two branched-chain amino acids isoleucine and valine have only a very weak effect in this respect (20, 21).

Clinically effective doses of HMB range from 2 to 3 grams, which you should take before training.

Is fasting cardio best in the morning?

This is a frequently asked question - especially among intermittent fasting followers. And the answer is simple: the advantage of doing cardio in the morning when fasting is that you can ensure that your insulin levels are really at baseline.

This is also the reason why research shows that fat oxidation rates are highest after 6+ hours of fasting (22). And this is also why many people who do cardio in a fasted state do it after waking up and before breakfast. It simply works well.

However, I don't think you have to do fasted cardio first thing in the morning to maximize the benefits of this type of training. You can also ensure that you are in a fasted state by planning your meals accordingly.

Studies have shown that just 35 grams of sugar is enough to raise insulin levels above baseline for several hours (23). In another study, a mixed meal containing 75 grams of carbohydrates, 37 grams of protein and 17 grams of fat increased insulin levels for over 5 hours (24). Even a serving of whey protein is digested over several hours and raises insulin levels (25).

All of this means that you can't expect to eat a big lunch and be back in a fasting state by 17:00.

Here's how I do it:

  • I do a training session with weights in a fasted state first thing in the morning before my first food intake.
  • I drink a whey protein shake after training.
  • I eat a light lunch consisting of a salad with 200 grams of chicken.
  • I take another scoop of whey protein at 15:00.
  • I do my cardio training at 18:00.
  • I eat dinner after my cardio workout.
  • I eat another big meal at 21:00.

As you can see, my calorie and carbohydrate intake is low until dinner. This ensures that my insulin levels stay low too. As a side note, I would not be in a fasted state at 6:00 pm if my meal at 3:00 pm was larger, but 3 hours is enough time to fully digest a meal consisting of only 20 to 25 grams of whey protein (26).

Should I eat something after a cardio workout in a fasted state?

If we are only talking about fat burning, then continuing to fast after a workout would make sense. The fat-burning chemicals that your body released during the workout are still in your bloodstream.

The problem, however, is that muscle breakdown will increase after training if you don't eat (27). And stopping this takes precedence over squeezing out every last gram of fat loss. Some people take another serving of HMB or BCAAs after training to extend the fast by an hour or two. This is of course an option, but I don't think it makes much sense for two reasons:

1. catecholamine levels quickly return to baseline shortly after you stop exercising (28).

This raises the question of how much extra fat you are actually burning by waiting to eat.

2 It's expensive

If you take a serving of HMB or BCAAs before and after your workout...and if you do this for multiple workouts per's going to hurt your wallet. That's another reason I break my post-workout fast and eat a high protein meal.

My program for cardio training while fasting

Before I recap everything, I want to share with you a simple "do this and lose fat faster" program that has served me and many people I've worked with well.

It all starts with a 25% calorie deficit, a high protein diet and 4 to 5 hours of heavy weight training and 1.5 to 2 hours of HIIT cardio per week.

Remember that no amount of supplementation will matter unless you are doing everything right in your diet. However, once you've got your diet on point, supplements can be a valuable support.

My program looks like this:

Before training with weights in a fasted state

About 15 minutes before my fasted weight training session, which I do in the morning about 45 minutes after waking up, I take the following:

  • A pre-workout supplement containing, among other things, L-citrulline and beta alanine
  • 200 mg caffeine
  • 2 to 3 grams of HMB

My training session with weights lasts about 45 to 60 minutes and then I eat my first meal of the day, which contains about 50 grams of protein.


I eat a light lunch that consists of a salad with chicken and a scoop of whey protein so that I'm back in a fasted state around 5:30 to be able to do my cardio workout in a fasted state. I don't take any fat loss supplements with my lunch.

(At this point I would like to mention that I take a scoop of whey protein around 15:00, which gives my body about 2.5 to 3 hours to digest this protein before cardio training).

Around 17:30, before the cardio workout

About 15 minutes before performing my cardio workout in a fasted state, I consume the following:

I then do 25 minutes of HIIT cardio training on the ergometer and then have dinner.

Conclusion on cardio training (and training with weights) in a fasting state

Exercising while fasting is not a magic silver bullet, but if you follow my advice from this article, it will help you lose fat faster while maintaining your existing muscle mass. This is especially true if you are struggling to lose fat in problem areas (the abdomen for men and hips and buttocks for women).

If fasting cardio doesn't work or isn't practical for you for whatever reason, don't worry. You can achieve the same results if you exercise in a postprandial/fed state - it just might take a little longer for those stubborn love handles on your body to dwindle.




By Michael Matthews

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