Intermittent fasting is a great tool to help you lose weight.
My clients and I have been using it for many years, but there seems to be a lot of confusion out there about what I.F. can and cannot do, so I put together this comprehensive blog post to clear everything up.
Let’s get stuck in!

How Does Intermittent Fasting Work?
Simple; calorie control.
The idea is that by fasting for the majority of the day and then consuming all of your calories within an allotted “feeding window” e.g. 12pm-8pm) you will find it easier to stick to your calorie targets.
As such, intermittent fasting is not really a diet, but just a tool which we can apply alongside any diet we want; such as flexible dieting, clean eating, keto, a Mediterranean diet, or whatever else.
There are several different setups you can choose from. Some people prefer a 20/4 model (20-hours of fasting followed by a 4-hour feeding window), and others enjoy a more relaxed 14/10 model (14-hours of fasting followed by a 10-hour feeding window), but I’ve always preferred the 16/8 model, and it’s the one which most of my clients have enjoyed the best results with over the years.
So with the 16/8 model you’ll fast for 16 hours (this can include sleep through the night) and you’ll eat all of your calories within an 8-hour window. I like to put my “feeding window” from 12pm-8pm as this fits my schedule nicely, but you can really put it wherever you like.
See, I told you this was easy!

What Are The Benefits Of Intermittent Fasting?
Let’s face it; we all have a friend who makes I.F. sound like a cult.
They’ll claim it helped them with everything from weight loss, to their tax bill, to helping Guns N’ Roses reunite in 2015 when nobody thought it was possible!
Honestly, that type of “salesman-like” behaviour puts more people off than they realize, so let’s ignore all of their silliness and look at what science shows us are the main benefits of using intermittent fasting, shall we?
- Calorie control
As mentioned earlier, by cramming your daily food intake into a relatively small “feeding window” (as opposed to just eating when you feel like it) there’s a better chance you’ll stay within your calorie budget.
This keeps you consistent, and that’s how you achieve great results in the long run.
- Improve discipline
People like structure, and I.F. provides that structure.
Once you get into the habit of only eating between certain times of day you’ll notice how many unplanned snacks are wiped out of your weekly food diary. This healthy habit then gives you a good platform of discipline where you just don’t feel tempted outside of your meal times, a trait which most people never get the hang of via traditional diets.
- Additional health benefits?
You’ll often hear “gurus” wax lyrical about other health benefits which are supposedly unlocked via intermittent fasting, such as increased fat metabolism, or more energy, or even living longer, but these things don’t really have any scientific data to back them up just now. (1, 2, 3, 4, 5)
Rest assured if that changes then I’ll update this page, but for now I’d advised you to ignore any so-called “experts” who are over-complicating this process – because I guarantee they’re trying to sell you some bullshit supplements that you do not need!
Ex-Muscle & Fitness science chief Dr. Jim Stoppani is a big fan of using I.F., and he had this to say:

“I’m very passionate about fitness, but I also believe in enjoying life. Those two things can be extremely hard to balance! That’s why I’ve been following an intermittent fasting eating plan for the last few years.
I can fit my diet around my busy schedule quite easily, I get to eat the foods I want (within reason, of course!), and it helps me to maintain my physique.”
– Dr. Jim Stoppani, PhD

There Are 2 Types Of People Who Excel With I.F.
In my 22 years as a personal trainer, I began to notice a trend.
Intermittent fasting is not something which works for everyone (some people prefer more traditional diets), but there are two types of trainees who usually unlocked great results from it.
Do you fit either of these templates?
- Somebody who needs more structure
At their core, humans are creatures of habit.
We might like the idea of chaos, but we hate the reality of it.
This is especially true when it comes to our diets, and the rigidity of intermittent fasting can be really helpful for anyone who has previously found traditional diets to be a challenge.
Make no mistake, the first few days of I.F. will thump you harder than a bag of dicks, but once you get used to this structure you’ll see how it helps you avoid the unplanned snacks which used to derail your efforts. It normally takes about one week for this adjustment to happen, so stick with it during those first few days, and over time you’ll achieve a level of consistency which escaped you in the past.
- Someone who’s in the final stages of a fat loss transformation
During the final stages of a workout program, when calories are already restricted, it makes perfect sense to deploy I.F. to help make sure you stay within your daily targets.
By the time you reach this stage you’ve already achieved pretty good results and shown the discipline to hit your targets on a regular basis, but all diets take their toll over time, so using I.F. helps at this stage because the shorter “feeding windows” make it seem like you’re eating more food than you really are, and that’s often enough to help you get over the finish line in even the hardest of cutting phases.

Beware The Bullshit Advice
The worst thing about a diet (or in this case a dieting tool) catching on trend is that fucking imbeciles start popping up everywhere dishing out ridiculours advice.
That’s what happened with intermittent fasting over the last few years – just like it did for Adkins and keto!
Intermittent fasting has been around for many decades, but since it got trendy in 2010 we’ve seen a whole range of crazy new statements being made by so-called “experts” looking to trick people into buying bullshit they’re selling.
Let’s debunk some of those myths right now.
- “You can eat whatever you want within your feeding window!”
I’m sorry (I really am), but you really can’t eat whatever you want and expect to lose weight.
Trust me, if you could then I’d be all over it. The law of thermodynamics (“calories in versus calories out”) doesn’t give two fucks what you want to look like, or whether you’re using intermittent fasting, and there is no “trick” to put it into fat burning mode while still gorging on junk food. (7)
One of my old buddies fell for something like this many years ago, when a YouTube “expert” told him he could “eat anything at all between 6pm-10pm and not gain an ounce of fat” (cuz fasting brah!). He gained 35lbs in a fucking month.
- “I.F. can cure Type 2 diabetes!”
It’s not so much the fasting, it’s the fact that you’re getting regular exercise and controlling your overall calories.
A 2015 study actually showed that fasting has no effect on insulin response, so we can’t give it credit for ridding you of type 2 diabetes. (8)
- “I.F. helps you train harder!”
From right out of left field, it is claimed that intermittent fasting can help you train harder by improving the supply of oxygen to your working muscles.
This would fantastic if true (spoiler; it’s not) because it’s the exact same thing which athletes are trying to achieve when they take illegal substances to boost their performance!
Unfortunately, the improvement to oxygen supply which come via I.F. are so tiny you will not notice them in the gym at all, so let’s put this myth to bed! (6)

Intermittent Fasting FAQ
I recently asked my social media audience to give me their biggest questions about intermittent fasting for inclusion in this round-up.
Here’s the most commonly asked questions.
- Can you use intermittent fasting to build muscle?
You can, but only to a certain point. This is a tool where you’re cramming all of your daily calories into a relatively short window, so it makes sense how it could be useful on a fat loss diet, but someone who wants to gain size would need a calorie surplus so that might make them feel stuffed.
- What type of intermittent fasting model gets the best results?
I’ve always preferred a 16/8 model, but there isn’t a shred of evidence to suggest that one model is superior to another, so my advice is to choose the one which fits your lifestyle the best because this will help you to be more consistent.
- When should my “feeding window” begin?
In a perfect world I’d like your “feeding window” to begin as soon as your workout finishes, so you can replenish your hungry muscles and then move on with your day. We don’t live in a perfect world, of course, so there’s no reason to force this if you find it difficult. The main objective is overall consistency.
- Are there any foods which I can eat in my fasting period?
I was surprised to see this one pop up as often as it did. Fasting means no food, so the answer is no you fucking can’t. While we’re on this topic, I’ve seen a few social media “experts” telling people they can eat so-called “negative calorie foods” during their fasting period without breaking the fast. This is absolutely not true.
- Should I take any supplements during my fasting period?
If a supplement contains any calories then it’d break your fast just like food. This rules out things like whey protein, BCAAs, creatine, beta-alanine, citrulline, etc. I recommend keeping it simple during your fasting period by just drinking water, and add a caffeine supplement to it if you must.
- Why am I not allowed BCAAs during my fasting period?
This is one of the biggest myths in the supplement world. You see, most BCAA supplements list “zero calories” on the label, and fitness magazines often encourage people to “sip them all day long to avoid losing muscle” but there are two important things to consider here. The first is that BCAA supplements really do contain calories, they’re just not listed on the label thanks to a supplement industry loophole, and it will break your fast just like food would. The second is that muscle breakdown doesn’t occur anywhere near as fast as these charlatans are claiming, so unless you’ve got the training regimen on a full-time Olympic athlete you do not need BCAAs at all.
- Which foods should I eat during my “feeding window” for the best results?
Most people who read my website are trying to build a lean, muscular physique, so with that in mind I’d advise you to focus on:
- Being in a calorie deficit to achieve fat loss
- Eating around 1g protein/lb to enhance muscle retention
- Get 15-30 fibre/day via green vegetables to help your digestive system.
- Why do some people only fast at weekends?
Certain iterations of I.F. like “The 5/2 Diet” will have you eating normally through the week and then fasting for the whole weekend. Some people enjoy that, and ultimately it works the same way.
- Do you have any video guides to I.F.?
Yes, I did one ages ago: https://www.youtube.com/watch?v=zgN4E7Lnvc8. Enjoy!

References:
- Stewart, T. M., et al. Rigid vs. flexible dieting: association with eating disorder symptoms in nonobese women. Appetite (2002).
- Pilegaard, H., et al. Effect of short-term fasting and refeeding on transcriptional regulation of metabolic genes in human skeletal muscle. Diabetes (2003).
- Hildebrandt, A. L., et al. Exercise attenuates the fasting-induce transcriptional activation of metabolic genes in skeletal muscle. Am J Physiol Metab (2000).
- Mattson, M. P., et al. Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems. J Nutr Biochem (2005).
- Trabelsi, K., et al. Effects of Ramadan fasting on biochemical and anthropometric parameters in physically active men. Asian Journal of Sports Medicine (2011).
- Stote, K. S., et al. A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults. Am J Clin Nutr (2007).
- Swinburn B., et al. Increased food energy supply is more than sufficient to explain the US epidemic of obesity. Am J Clin Nutr (2009).
- Jakubowicz, D., et al. Fasting until noon triggers increased postprandial hyperglycemia and impaired insulin response after lunch and dinner in individuals with type 2 diabetes: a randomized clinical trial. Diabetes Care (2015).
I’ve been doing I.F. for the last two years and lost 20lbs and kept it off. One of the things which put me off is the cultish behavior some I.F. users have, dead right it’s all about calorie control Russ 🙂
I’ve really enjoyed doing IF 12/12 split. Makes shift work so much easier!
Started following IF through one of your earlier blogs. That was 2017, still going strong!
Loved this. Straight to the point, thanks.
I’m on week five now and loving it.
I have been doing 16/8 most days and it works great.
Exceрtіonally well written!