- The benefits to intermittent fasting are often claimed to be endless, but turn out to be relatively few.
- Intermittent fasting to lose belly fat works due to energy restriction and seems to be equally effective as continuous energy restriction (‘normal’ dieting).
- Fasting puts the body under more stress. While this doesn’t have to be a dealbreaker, it’s important to address your overall stress load first before possibly adding fuel to a fire.
Some of the most common benefits to intermittent fasting you’ll hear about are lowering inflammation, improving insulin sensitivity, autophagy, better gains, eternal youth, the magical fat torching benefits of fasted cardio, you name it.
Then on the other hand some people write off Intermittent fasting as ‘just skipping breakfast’ and put up posts like “X reasons to AVOID fasting”.
Once again, it’s black and white. It’s either THE solution to everyone’s problems or it’s completely useless.
In this article you will learn that the real answer probably lies somewhere in the middle. Without bias we’ll get into the benefits to intermittent fasting, but also the downsides. We’ll talk about what it is, how you can apply it, and discuss if it’s a possible tool in your toolbelt.
Before we jump in, real quick.. If you enjoy learning about nutrition but don’t always want to read it all, feel free to check out our video mini series ‘The Principles of Nutrition’.
Because educating yourself and learning how to adjust your behavior and lifestyle in a way that works for you and your goals, in my opinion, is the thing that will get you the sustainable results you deserve.
Will intermittent fasting work? Let’s find out..
What is IF? – Different intermittent fasting methods
Humans have always been fasting in some way, shape, or form. Voluntarily for religious reasons, or involuntarily for the obvious reason that if we didn’t find/catch enough food, we’d simply have to wait longer before our next meal. Let’s not forget that it’s a relatively recent luxury, having ALL of the food available ALL the time.
Sure these days you have a stacked fridge, there’s a supermarket around the corner, and we can literally have food delivered straight to our doorstep at the press of a button. But believe it or not, that wasn’t always the case.
And of course there’s the fact that you already fast on a daily basis, when you sleep! Guess where the word ‘breakfast’ comes from?
So what does ‘intermittent’ fasting mean?
Intermittent fasting, or intermittent energy restriction, is really an umbrella term for alternate-day fasting, periodic fasting, and lastly the thing that most people mean by saying intermittent fasting: time-restricted eating.
Common schedules for intermittent fasting include the popular 16/8 method, where you don’t eat for 16 hours (your fasting window) and you do eat for 8 hours (your feeding window) and the 5/2 diet where you eat for 5 days out of the week and fast for the other 2.
Some people even go to the extremes of not eating for multiple days in a row.
Should you fast?
Let me first ask you why you want to fast. Because the one and only answer is that it just depends. It can feel great and be equally effective depending on your goals, or it can absolutely suck and hold you back.
A couple of years ago, I overheard a conversation of someone who said “I’ve been intermittent fasting, have you heard about it? I can literally eat everything and anything I want, as long as I fast for 16 hours”. He then continued about how amazing he felt and that he wasn’t hungry at all.
I’ve also met people with the energy levels of a sloth, but the appetite of a Tasmanian Devil ready to devour a whole Kangaroo leg, including fur and bones (I’ve seen this in person, not a pretty sight).
You see, different people have different experiences with intermittent fasting. Some will notice being less hungry (1), while others may feel more hungry (2). Some people find that fasting helps them control their food intake, while others may develop binge tendencies. Some feel clear-headed and focused, and others walk around like a ticking cortisol timebomb.
Some of our online coaching clients are currently intermittent fasting, because they like it for adherence reasons. However most of our clients don’t follow a strict feeding window, simply because they don’t need or want to.
I remember the joys of fasting from 9pm all the way until I was done with my hour-long CrossFit session the next morning around noon. And by ‘joys’ I mean next level hangry-ness, zero energy, and often being told I looked gray while training. I was the leanest I’d ever been in my adult life, but also felt like complete dogsh*t.
But I don’t hate it. These days I tend to move breakfast a little later when I’m cutting, as it allows for more food later in the day which I enjoy.
So what’s it going to be for YOU? Should you fast?
There’s only one way to find out, and that’s by learning about it, deciding if it makes sense for your preferences and goals, and possibly trying out intermittent fasting for yourself.
Intermittent fasting for muscle gain and fasted exercise
To get the most out of your training, which only acts as the stimulus, you’re going to want to sleep plenty and at least eat within your maintenance calorie range, or even a slight surplus. This CAN be done while restricting your feeding window, however there may be a few downsides to intermittent fasting for muscle gain.
Protein to maximize muscle growth
The myth of ‘not being able to digest more than 30-40g of protein in one sitting’ comes from the fact that bigger portions don’t necessarily give you any MORE benefits when it comes to muscle protein synthesis (3), aka muscle building. Because your feeding window is much shorter, it’s also going to be much more difficult to get those ‘optimal’ portions of protein in.
That means that if muscle gain (or maintenance) is a priority, you may be better off spreading your protein intake evenly throughout the day rather than having a handful of really big portions.
Now if you don’t necessarily care about what seems to be ‘optimal’ (which is totally fine by the way), then feel free to fast. Because even when your protein portions are more than 40g, your body will still digest it all (4).
Carbohydrate to fuel training
Also when it comes to carbs, restricting your feeding window might not be optimal. Since carbohydrate is your body’s preferred fuel source for higher intensity training like resistance training, it can help you train hard/effectively enough to provide your body with the right stimulus.
Because your workouts are mostly fueled by glycogen (which takes time to replenish) your evening dinner is going to be more important than your breakfast for your morning workout.
A lot is going to depend on the intensity of your training, how long your sessions are, and more. But if performance and/or muscle gain are a priority, then you’ll likely benefit from getting some carbs in before training. See it as ‘extra fuel’ that’s floating around in your bloodstream so it doesn’t all have to come from your muscle glycogen stores (5).
Conclusion: Should you practice intermittent fasting for muscle gain?
Depending on your experience in the gym, you may want to approach your muscle building goals differently. However the most important factors are always going to be exercise, sleep, energy balance and macros. If you can manage those, great. But outside of that intermittent fasting does not seem to have any additional benefits for muscle growth (6).
At the end of the day it’s much more about the total amount of calories/nutrients you’re getting in, rather than your meal frequency and timing. However if you’re trying to build as much muscle as possible, then it may not be the best approach for you.
Especially in a calorie deficit I’d say let’s put the muscle building goals on hold for now, because it simply wouldn’t be the right environment for your body to build new tissue that’s both very calorie-expensive to build AND maintain.
What Is The Best Intermittent Fasting Window To Lose Belly Fat?
Fasting works for fat loss because it helps you restrict calories. With less time to eat, you tend to automatically eat fewer calories altogether. That’s really all there is to it when it comes to fasting for fat loss.
When calories are equated, there does not seem to be any difference between intermittent fasting and continuous energy restriction for fat loss, as well as other health benefits (7-8).
Intermittent fasting to lose belly fat CAN be a great approach, because it can help you stick to your energy balance.
But remember how some people experience less hunger, while others turn into Tasmanian Devil? Fasting also can totally backfire.
If it makes you feel frustrated and hangry and if all you can think about is your next meal, then there’s a good chance you might overeat within your feeding window. What started off as a calorie deficit, can quickly turn into a calorie surplus.
Conclusion: Should you intermittent fast to lose belly fat?
It depends. Does it help you stick to your calorie deficit? Great! Then let’s use it to your advantage. Does it turn you into a Tasmanian Devil, then let’s maybe skip it. Because no one benefits from binging at night after trying to not eat at all for hours on end.
Other applications for intermittent fasting
Before I let you go, there are a few more points to discuss: autophagy, gut health and stress. Because you’ve already been reading for a little while, I’ll keep it more to-the-point here.
Fasting and autophagy
Autophagy is the process of getting rid of damaged cells and replacing them with new, healthy cells.
This happens when you fast, but also when you just eat in a deficit (9) without time restriction. So if it’s specifically for autophagy, then there’s no reason to fast.
Fasting and gut health
If you’re struggling with digestive upset, then fasting from time to time might be a way to give your gut a bit of a break.
If those are dialed in and you can’t figure out what’s causing gut issues, then I suggest talking to your doctor to explore what could be the cause.
Fasting and Stress
Fasting seems to have a very strong effect on your cortisol levels (10). Now cortisol (the main stress hormone) isn’t inherently bad, but constantly elevated cortisol levels come with a plethora of negative outcomes.
That’s not to say you should never fast just because it puts your body under more stress. But that does mean that addressing your overall stress load first might be a good idea.
Already super stressed? Then maybe it’s not the best idea to add more stress to the body. The dose makes the poison.
Will intermittent fasting work you?
So should you fast? You tell me.
Before running with intermittent fasting I recommend considering both the pros and cons and making an educated decision on what you think might serve your goals the best.
Does it help you adhere to your nutrition, do you want to see if it can give your digestive system a bit of a break, or do you just not enjoy eating breakfast? Then intermittent fasting may be a great tool.
Is it for any other health benefits, then you could also eat in a calorie deficit from time to time.
If you’re not sure, then talk to a doctor or qualified coach who can point you in the right direction. As much as I’d like to give you all the answers to YOUR questions in these articles, reality is that everything will depend on the context.
Do you have more questions regarding this topic? Then go ahead and DM me here, I’m always happy to help.
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- Ohkawara, Kazunori et al. “Effects of increased meal frequency on fat oxidation and perceived hunger.” Obesity (Silver Spring, Md.) vol. 21,2 (2013): 336-43. doi:10.1002/oby.20032
- Frecka, Julie M, and Richard D Mattes. “Possible entrainment of ghrelin to habitual meal patterns in humans.” American journal of physiology. Gastrointestinal and liver physiology vol. 294,3 (2008): G699-707. doi:10.1152/ajpgi.00448.2007
- Trommelen, J., Betz, M.W. & van Loon, L.J.C. The Muscle Protein Synthetic Response to Meal Ingestion Following Resistance-Type Exercise. Sports Med 49, 185–197 (2019). https://doi.org/10.1007/s40279-019-01053-5
- Schoenfeld, Brad Jon, and Alan Albert Aragon. “How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution.” Journal of the International Society of Sports Nutrition vol. 15 10. 27 Feb. 2018, doi:10.1186/s12970-018-0215-1
- Haff, G Gregory et al. “Carbohydrate supplementation and resistance training.” Journal of strength and conditioning research vol. 17,1 (2003): 187-96. doi:10.1519/1533-4287(2003)017<0187:csart>2.0.co;2
- Moro, T., Tinsley, G., Bianco, A. et al. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. J Transl Med 14, 290 (2016). https://doi.org/10.1186/s12967-016-1044-0
- Seimon, Radhika V et al. “Do intermittent diets provide physiological benefits over continuous diets for weight loss? A systematic review of clinical trials.” Molecular and cellular endocrinology vol. 418 Pt 2 (2015): 153-72. doi:10.1016/j.mce.2015.09.014
- Harvie, M N et al. “The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women.” International journal of obesity (2005) vol. 35,5 (2011): 714-27. doi:10.1038/ijo.2010.171
- Bagherniya, Mohammad et al. “The effect of fasting or calorie restriction on autophagy induction: A review of the literature.” Ageing research reviews vol. 47 (2018): 183-197. doi:10.1016/j.arr.2018.08.004
- Nakamura, Yuko et al. “Systematic review and meta-analysis reveals acutely elevated plasma cortisol following fasting but not less severe calorie restriction.” Stress (Amsterdam, Netherlands) vol. 19,2 (2016): 151-7. doi:10.3109/10253890.2015.1121984