You guys remember when Zoolander dropped in 2001 and Will Ferrell’s Mugatu character couldn’t stop obsessing over Hansel’s hotness?
That’s how I feel about fasting right now in the fitness industry.
Some people think it’s an amazing dietary strategy to help with fat loss (and sometimes even muscle gain) while others believe it’s suboptimal to having more consistent protein feedings across the day in order to maximize muscle protein synthesis.
Some people will tell you it improves insulin sensitivity and boosts natural testosterone levels while others would lead you to believe that it’s putting you at risk of muscle loss.
So which is it?
And why does it always feel like the fitness industry is exploding with conflicting claims?
These are good questions, which I hope to address (in part) in this article.
Here’s what you can expect:
I’m going to avoid speaking about any health benefits of fasting outside of weight loss in order to respect my scope of practice. In other words, I’m not going to be taking a position on whether fasting can help us live longer lives or improve our hormone profiles.
So as for all of that insulin sensitivity and testosterone talk, you won’t see me addressing those claims (even though I find them fascinating and worthy of your own independent exploration).
Instead, I’m going to tell you how to use fasting simply as a form of caloric restriction to help you improve your body composition primarily through fat loss.
I’m going to provide practical examples of how I’ve used single-day fasting in my own body recomposition effort.
I’m going to outline the advantages of single-day fasting when compared to other more traditional forms of caloric restriction.
How to Use Single-Day “Semi-Fasting” to Improve Your Body Composition
Although there are several ways to use fasting to improve your body composition, I’m going to focus the attention of this particular article on one specific strategy, which is…
Single-day fasting.
In other words, I think a lot of people would benefit from fasting for one entire day a week.
Sound crazy?
Maybe in context of our modern dietary patterns, but keep in mind that our modern dietary patterns have led 42% of people into a life of obesity, which is why I think a creative reconsideration of our eating habits surrounding the idea of sustainable body composition improvement is a very good idea.
So what’s up with not eating for an entire day? How is that supposed to help anyone with a body recomposition goal?
Simply put, it’s a very basic way of reducing your weekly caloric consumption.
In short, it helps you get into a caloric deficit to help you lose body fat.
We really don’t need to make it any more complicated than that, but we’ll dive into a bit more nuance in the following section.
That being said, if fasting for an entire day seems daunting and overwhelming, you could easily modify your strategy by fasting through the majority of the day and then enjoying one large, nutritionally-dense meal for dinner.
This is what I personally refer to as “semi-fasting” but only in the sense that you’re fasting for most of the day instead of complete 24-hour period. I understand that you can’t technically “semi-fast,” so take that terminology with a grain of salt.
Ultimately, it would be better described as a very low-calorie day relative to one’s normal intake.
When I do this myself, I usually have an 800-1,000-calorie smoothie packed with greens, plant-based protein powder, berries, bananas, nuts, and seeds around 5PM.
Or I might opt for an enormous tofu salad with a plethora of leafy greens drizzled in tahini and sprinkled with hemp hearts and walnuts.
The objective (for me) is simply to eat one nutritionally-dense meal with plenty of protein, which makes smoothies and salads great options given how easy it can be to pack them full of fruits, vegetables, nuts, seeds, and lean proteins like protein powders or soy products.
What I like about this modified idea is that I never have to go to bed hungry, but I can still reap the benefits of a restricted eating window.
And, of course, eating once per day tends to be much easier to adhere to (for most people) than an overnight fast.
In fact, this modified “semi-fasting” approach is what you will see illustrated in the upcoming examples as I have applied it to my own lifestyle (as opposed to a full day of fasting).
Why might a SINGLE-day weekly “SEMI-fast” help with fat loss?
As I mentioned briefly above, there doesn’t seem to be anything “magical” about fasting when it comes to losing body fat other than that it serves as a very simple way of reducing your overall intake.
But I think another underrated benefit of single-day “semi-fasting” is that it helps you start thinking of your caloric deficit in the context of one week instead of a single day.
In fact, this is what I do with all of my fat loss clients and it's why things like carb cycling and high/low approaches work for bodybuilders.
As long as the caloric math makes sense at the end of the week, the fat loss is always systematic and exciting.
For example, you may have heard that 3,500 calories equal roughly one pound of body fat.
So, if you can get yourself into a 500-calorie daily deficit, you'll be cruising toward about one pound of fat loss per week because 500 calories multiplied by 7 days equals 3,500 calories.
Boom. Math, right?
But sometimes people get too caught up in the "24-hour-ness" of it all.
In other words, people focus too much on that 500-calorie daily deficit when they could be acting more strategically on a behalf of a 3,500-calorie weekly deficit.
I’ll use myself as an example here.
If my maintenance calories are around 3,300 calories right now, we could say that a daily intake of 2,800 calories might lead to approximately one pound of fat loss per week based on the math we just discussed.
Because of that, I could structure my weekly (non-fasting) eating pattern like this:
Standard static Weekly Calorie Example
The standard static example would look like this:
Monday: 2,800 calories
Tuesday: 2,800 calories
Wednesday: 2,800 calories
Thursday: 2,800 calories
Friday: 2,800 calories
Saturday: 2,800 calories
Sunday: 2,800 calories
As you can see, this is simply the “eat the same number of calories everyday” approach that many people ascribe to for the sake of consistency and routine.
But a one-day “semi-fasting” example could allow you to eat more during the week while eating much less just once per weekend.
This is cool because you could choose to eat more carbohydrates to bolster your weekday workouts knowing you can rest up and eat less (or nothing) on Sunday.
Here is an example of what that could look like (and what I often do):
One-Day “Semi-Fast” Weekly Calorie Example
Monday: 3,100 calories (+300)
Tuesday: 3,100 calories (+300)
Wednesday: 3,100 calories (+300)
Thursday: 3,100 calories (+300)
Friday, 3,100 calories (+300)
Saturday: 3,100 calories (+300)
Sunday: 1,000 calories (-1,800)
In this example, limiting myself to just 1,000 calories on Sunday allows me to eat an extra 300 calories on each of those other six days per week. Keep in mind too that those +300 calories in parentheses are relative to the deficit, which means this entire week of eating is still designed for fat loss.
Three hundred calories may not seem like much, but that's an extra PB&J and a glass of almond milk that you could apply to a important pre or post-workout meal.
But again, this is just one way to do it.
If you really want to be a Level 1000 Fat Loss Ninja, you could nuance your daily caloric intake even further by biasing your calories toward your most intense workouts or even planned, higher-calorie social occasions while utilizing single-day fasting over the weekend.
Check out what I mean in the following example:
Level 1000 Fat Loss Ninja Weekly Calorie Example featuring a One-Day Semi-Fast
Monday: 3,400 calories for a nasty leg day because you want that peach (+600)
Tuesday: 3,100 calories for an upper body day (+300)
Wednesday: 2,800 calories for a rest day (0)
Thursday: 3,100 calories for a normal leg day (+300)
Friday: 3,400 calories because pizza with the boys (+600)
Saturday: 2,800 calories because math (0)
Sunday: 1,000 calories (-1,800)
Do you have to make it this complicated? Of course not.
I just want to illustrate that you have the freedom to do so if you like the idea of heavily nuancing your caloric consumption based on fluctuations in your training routine and lifestyle overall.
All three of these options add up to 19,600 calories per week, which means the fat loss in each situation would be almost identical while all other factors remain equal.
Pretty cool, yeah?
You could easily do similar math with your own numbers.
Just remember that these numbers were calculated for someone with a maintenance calorie intake of 3,300.
I also have a few opinions on why I think this can work really well for people.
Advantages of “Semi-Fasting” Once Per Week
It's easy to fast for one day when you know you get plenty of food the very next day.
I like to think of this as the "light at the end of the tunnel" effect. For those of you who have never fasted before, this may still seem extreme, but it's really quite doable once you commit.
Plus, if you've ever dieted before, you know that the worst part of dieting comes from being randomly hungry on a Monday and knowing it ain't getting any better for the next six weeks. This dieting pattern fights against that drudgery.
You're unlikely to downregulate your metabolism by fasting just once per week.
I don't pretend to be an expert on metabolic downregulation outside of plenty of anecdotal experience from working with my own clients, but to me it just makes good sense that it might be better for keeping your metabolism churning along to duck your calories hard once per week versus committing to a peasant's 1200-calorie diet for weeks and months on end. It's almost like your body senses that there is no need to process energy more efficiently when it knows more food is coming soon. Anecdotally, I have seen this work time and time again. And, although I wouldn’t call it “biohacking,” I do think it’s a creative way to manipulate your caloric consumption.
It gives your digestive system a break, which I personally think may have some exciting health benefits.
In my own experience, it can also create a refreshing feeling of emptiness as the fast goes on, which leaves me feeling acutely lighter.
It exercises your discipline muscle.
In a modern gimme-gimme culture where we tend to complain about anything we can’t have instantaneously, I find it grounding to limit my food consumption once per week.
I also personally think this translates well into other areas of life.
For me personally, my stomach starts feeling noticeably tighter around 1-2PM, but this is of course just my own experience and a small psychological benefit I enjoy.
Disadvantages of “Semi-Fasting” Once Per Week
Some people will never be able to handle the acute hunger of even a half-day fast, and that’s fine.
I’m not here to try to convince anyone to be hungry if you’re not bought into the benefits beyond the hunger (and I mean that sincerely).
It might be difficult to navigate certain social situations like dining out with friends if you and your significant other are social people on the weekends.
For my own lifestyle, Sundays tend to be very relaxed, so this isn’t an issue for me personally in most cases, but I think it’s worth mentioning in case it applies to others.
Your Monday workouts might feel a bit lethargic if you don’t prioritize a massive, carb-heavy breakfast to replenish yourself from the low-calorie day prior.
And again, you obviously don’t have to choose Sundays for your “semi-fast.” This was just the example used consistently throughout this article (and what I do personally).
Summary
I think single-day fasting is an underrated form of caloric restriction that could help a lot of people lose body fat sustainably.
Single-day fasting can be a helpful strategy to help people think of their caloric deficits on a weekly basis instead of a daily basis.
“Semi-fasting” once per week can allow you to eat more food during the week to fuel your most intense training sessions.
Practically speaking, I personally like to fast through the first half of the day and then eat one large, nutritionally dense meal around 5PM.
This is usually a large smoothie or a big tofu salad.
I really enjoyed writing this short article, so if you found it helpful, do me a favor and send it to someone in your life who finds body recomposition banter just as entertaining as you do.
Until next time,
-Andrew
