Intermittent fasting for fat loss without losing muscle

by | Health & Fitness

This article is about the discipline of intermittent fasting (IF) and the several health benefits of IF research has discovered. In short it sheds fat, allows for lean muscle gains, increases general health and has several neurological benefits. Sounds good right?

Well to be clear, IF is not the single magic bullet to optimum health and it does not make you ripped straight away. You should see it as just another tool you can use to improve your body composition and health. It can be used by both men and women. Let’s have a look at what intermittent fasting is and how you could use it.

What is intermittent fasting?

In summary IF is a diet approach where a person fasts in intervals. There is a long period of no food intake followed by a relatively brief period where you do eat.

A great example of an IF diet is the one of Martin Berkhan from the website Leangains. His approach consists of a period of fasting for 16 hours and a feeding window of 8 hours. You focus on three meals a day where you take the majority of your calories (especially carbohydrates) after training.

With three meals per day the setup where you fast for 16 hours could be:

  • 12 AM – 1 PM: Meal one with approximately 20 -25 % of your daily total calorie intake
  • 4 PM – 5 PM: Pre workout meal with again 20 – 25 % of your daily total calorie intake
  • 6 PM – 7 PM: Workout
  • 7 PM – 9 PM: Post workout meal which contains the remaining 50 – 60 % of your daily total calorie intake
  • On resting days you consume 50 – 60 % of your daily calorie intake at your first meal.

There are some rules that you need to stick to make this approach to IF work. The most important ones are:

  • Consume more carbs and less fat on training days.
  • Consume more fat and fewer carbs on resting days.
  • Eat high protein on all days.
  • You should not take in any calories during the fasting phase. Tea, coffee and other fluids with no calories are allowed.
  • For muscle gain it is advised not to train in a fasted state.
  • If you want to gain muscle you should eat above your maintenance. If you want to lose fat you still need to eat below maintenance.
  • It takes some experimenting to find the right caloric need when you use IF to achieve your goals.

Another example of intermittent fasting is eat stop eat by Brad Pilon. This style of IF consists of not eating for 24 hours once or twice a week. When you use this protocol it does not matter if you start your fast in the morning, midday or evening. You just fast for 24 hours whenever it is convenient for you to do so.

There is also alternate day fasting where you always alternate between a fasting day and a feeding day for a certain period. Alternate day fasting is the protocol used in most scientific studies on the subject.

The possible benefits of intermittent fasting

There are a lot of possible health benefits that your body produces when you are in a fasted state. They range from increased beneficial hormonal state for fat loss and muscle gain, improvement of general health and improvement of certain brain functions. So what does the research say? Lets look into that:

  • IF decreases insulin levels. This is logical since high insulin levels inhibit the release of stored body fat. If a fast does not decrease insulin levels your body will not be able to get energy from stored body fat [1].
  • According to this study [2] insulin sensitivity increases when a person intermittently fasts. If insulin sensitivity is low the cells in your body don’t respond well to insulin. Insulin resistance is a contributing factor to type 2 diabetes and it also promotes fat storage [3].
  • IF increases the amount of growth hormone in your body [4] [5]. The amount of growth hormone stimulates the release of body fat and promotes muscle growth [6].
  • You can lose weight with a normal caloric restriction and intermittent fasting. Intermittent fasting may however increase the likelihood of muscle preservation when shredding body fat [7] [8]. This study and personal findings of Martin Berkhan show that a larger proportion of lean mass is retained when doing intermittent fasting as opposed to just a daily caloric deficit.
  • Cognitive effects: Increase of catecholamines during fasting can have a positive effect on mental focus and concentration. You can also work for a long time without having to worry about food intake. These two things combined can increase your productivity.
  • Reduced risk of coronary heart disease [9]. Coronary heart disease is a leading cause of death among men and women in the world.
  • The promotion of neuronal autophagy. Neuronal autophagy is the process where cells recycle waste material and repair themselves. Your brain functions are highly dependent on neuronal autopgahy. Remove this process and your brain will not function well [10] [11].
  • When you fast levels of BDNF (brain derived neurotrophic factor) increase [12] [13]. This promotes the growth of new neurons and the development of synapses. Alzheimer’s disease is linked to low levels of BDNF and increasing BDNF has neurological benefits that combat Alzheimer [14].
  • Ketosis: Intermittent fasting can bring you in ketosis. This is a process where the body converts fat stores for energy. This releases ketones that can be used by your brain for fuel. Ketones are good for your brain [15].

The possible negative side effects of IF

Of course there are also some negative side effects that could arise from intermittent fasting. The negative side effects to intermittent fasting:

  • You can experience mental fog and hunger, especially if you eat a lot of junk food and food that spikes your insulin all the time. Your body will be adapted to burn glucose and fat burning will take a while to really get hold. First try and eat more paleo (less carbs) then try intermittent fasting.
  • This study suggests that intermittent fasting could have a negative effect on reproduction [16].
  • If you have certain health issues always consult your GP or do good research on intermittent fasting before you decide this is for you. Also note that a lot of the studies or done on animals and this means that the effects of intermittent fasting in humans could be slightly different.
  • It is important to note that you probably still need a caloric deficit if you want to lose weight overall. Don’t make intermittent fasting an excuse for binging on unhealthy foods and then blaming intermittent fasting for not achieving your weight loss goals. The same works the other way around for people who want to gain weight (muscle). You guys still need to eat above your maintenance caloric need.
  • Fasting too long for a period of 20 to 48 hours is problematic for muscle gain since proper post-workout nutrition is beneficial for gaining muscle [17].
  • It is not clear if working out after you have fasted for several hours is beneficial. There are studies that suggest that it is [18]. You can try it, but eat after training since proper post-workout nutrition is advised.

My own experience

I have been doing intermittent fasting for a while now. The main thing that I really like about Intermittent fasting is the fact that I don’t have to eat breakfast in the morning. My most productive hours are right after waking up and it is great to skip breakfast and start working. I also feel really focused and energized during the period until my first meal and It was the easiest thing ever to wait until 2 o clock to have my first meal.

I only have some statistics about the first 4 weeks. I started with 15.5% body fat and lowered it to 14%. At the same time I gained 1 kilo. According to my statistics my muscle mass went from 42.1% to 44.8%. For me this was great progress since I never lose fat and gain muscle at the same time and have a hard time gaining.

Positive vs negative

For me the positives outweigh the potential negative effects by a mile. Are you not convinced? Then consider that losing weight with intermittent fasting is a lot easier for most people then caloric restrictions at every single meal. Diet compliance is greater on an intermittent fasting approach [19] for weight loss.

Skip breakfast or fast for a day and your body becomes a fat burning machine without you having to hold back every single meal. The research also suggests that you will be more likely to maintain more lean body mass compared to normal caloric restriction. So want to lose weight (fat) the easy way? Try intermittent fasting.

Are you going to join me?

Do you want to try intermittent fasting? Then join me and do your own intermittent fasting challenge. Also let me know what you guys and girls think of intermittent fasting. Have you tried it yourself? Do you agree with the possible health benefits? Let us know.

PS: Also look at the websites Leangains and Mark’s Daily Apple if you want more info on this. Thanks to those guys I discovered intermittent fasting and I also used their ideas and research to write the article above. I recommend them.


Thomas is the co-founder of Amstermind. He empowers people by teaching them how to master their inner world. He is a meditation coach, reality explorer, herbal tea addict and internet entrepreneur. In his content he likes to combine personal development and spirituality.

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