Flexible dieting, often referred to as “if it fits your macros” (IIFYM), is taking the fitness industry by storm right now.
Everyone from industry experts, to competitors, to armchair critics have all given their 2 cents on IIFYM.
As you might expect, opinion is fairly divided. There are plenty of ardent proponents of this kind of dieting protocol. But there are just as many people who claim IIFYM is the worst thing to hit the fitness industry in decades.
When opinion is so polarized, it’s hard to find the truth. So, let’s try to have an impartial look at IIFYM.
What is Flexible Dieting?
To start with, what does “flexible dieting” actually mean?
To put it as simply as possible, “flexible dieting” or IIFYM is where you can eat whatever you like so long as it fits within your daily macronutrient targets.
When setting up an IIFYM-style diet, you would start by calculating your daily caloric requirements, just as you would when starting any other diet.
Once you had worked out how much you needed to eat to lose weight, you would divide up those calories into macronutrients: fat, carbohydrate, and protein.
When trying to retain muscle mass, most people calculate their protein requirements, and then divide their remaining calories between carbs and fats at a roughly 1:2 ratio.
Of course, there’s a lot of leeway here. If you think you need slightly more carbohydrates because you are more active than most people, you can adjust your macronutrient targets accordingly.
The important thing is that, once you have your macro targets for each day, you stick to them.
What you eat and when you eat it is not the overriding concern; the priority is sticking to your macro targets every single day.
With a diet of so few rules, it’s inevitable that many would misrepresent it. There’s currently a lot of false information floating about on the internet regarding IIFYM.
Let’s try to put some of those myths to rest.
What Flexible Dieting Isn’t
For starters, IIFYM is not a diet where you can just eat donuts and Skittles every day, and see great results.
It assumes the person following it is going to be reasonable with their diet. It assumes they know the basics of good nutrition; that they care about health, longevity and performance, and they know how to eat for those things.
Another thing that IIFYM is not is a silver bullet.
Despite what you might see on some fitness blogs, IIFYM or “flexible dieting” does not represent a magic cure for excess body fat or muscle mass retention.
Of course, if you don’t have the discipline or the knowledge to execute IIFYM dieting properly, then a traditional ‘clean eating’ type diet is vastly superior.
Many people think IIFYM is a license to eat a ‘cake and ribs’ diet. Others don’t know how to properly calculate their maintenance caloric requirements. Some people also clearly don’t know how to properly calculate their ideal macronutrient targets.
In these instances, the discipline demanded by a classic bodybuilding diet is necessary to keep people on track.
But if you have the discipline and the knowledge to set up your diet properly, IIFYM does not have any significant advantages or disadvantages in terms of fat loss or muscle preservation when compared to other diets.
All diets that put you in a caloric restriction lead to fat loss. The rate of fat loss is determined almost entirely by the extent of the caloric deficit.
If you start eating 600 calories below your maintenance level (the amount you need to stay the same size), then you will experience dramatic fat loss but also a significant degree of muscle loss.
If you set your calories at 50 below your maintenance level, you’re unlikely to see any movement at all. This is because you will either miscalculate calories on some days or you have miscalculated your maintenance level. A bigger margin is needed.
As with all things, the ideal deficit is somewhere in the middle. Training is also a factor, but ultimately everything comes down to the age-old and often over-looked equation: weight change = calories in – calories out.
So if you decide to leave your “clean eating” diet for a few months and adopt an “if it fits my macros” attitude, you wont see the numbers on the scale start to tumble overnight.
Nor will you start losing fat without losing any muscle mass or strength whatsoever.
Your rate of fat loss and muscle wastage is determined by the severity of your diet, your training, and other factors such as recovery and individual physiology. It is not determined so much by what you eat or how you eat it.
What Flexible Dieting Is
Many people attack IIFYM on exactly these terms.
They claim that it does not deliver results any different to traditional forms of dieting.
According to some, IIFYM is little more than a scam.
Yet the biggest proponents of flexible dieting almost never claim that IIFYM delivers more rapid fat loss or less muscle wastage than ‘clean eating’ or other more familiar forms of dieting.
Instead, most of the most enthusiastic fans of flexible dieting claim that it delivers practically identical results as ‘clean eating’ without forcing you to eat boring, repetitive, unsatisfying food.
So the main benefit of IIFYM over traditional diets isn’t the quality of the results. It is the ease of execution.
Let’s use an example.
Imagine you’re out with a group of friends. None of your friends are serious weightlifters, so they don’t pay too much attention to their diet.
Your friends might all decide that they want to go to a burger joint for dinner.
If you’re dieting in the ‘clean eating’ sense, you’d either have to turn your friends down, or be the guy who orders a plain, low fat burger patty and a side salad.
If you’re following a flexible dieting protocol, you can go and enjoy a greasy burger with your friends. You would simply calculate your remaining macros for the day and eat accordingly.
You aren’t achieving a better physique or more rapid muscle growth this way, but you are having a normal life, eating the food you find enjoyable when you want to eat it.
That also means there’s no meal prep, and no forcing meals down your throat when you just aren’t hungry.
If you are out with friends and you’re following a traditional, bodybuilding-style diet, you might have to bring our own food with you to ensure you can eat at the right time.
If you’re following IIFYM, it’s OK to go 4-5 hours without eating. You would simply have to make up for it later on in order to hit your macronutrient targets for the day.
So the main benefit of IIFYM is that it allows you to live a normal life while still keeping you on track for your goals, be they strength, athletic performance, or aesthetic in nature.
Is IIFYM For You?
Obviously then, whether or not you should follow an IIFYM-type diet depends on your specific goals.
If quality of outcome is our absolute, number 1 concern, then a classic bodybuilding diet is probably the way to go.
The ‘chicken and rice’ diet is incredibly boring, but it undoubtedly gets results. That kind of ‘clean eating’ approach to dieting has been used by strength athletes and professional bodybuilders for decades, and it is unlikely to lead you astray.
However, if you have no interest in trying to become the next Mr. Olympia, and you just want to have the best physique you can while still having a normal, stress-free life, then IIFYM is probably for you.
“Flexible dieting” or IIFYM still requires discipline, knowledge, and hard training to bring about the desired results.
You need to accurately calculate your caloric requirements, your ideal macronutrient breakdown, and then you need to hit those targets every day (without going too far over or under).
You also need to be working hard in the gym. While nobody grows muscle in the gym, without sufficient stimulus, there’ll be no growth no matter how good your diet is.
Yet IIFYM is undoubtedly easier, both mentally and practically, than the usual ‘chicken and rice’, 6 meals a day diet followed by many professional and amateur bodybuilders.
It allows you to eat like a normal person.
Sure, Mr Olympia can justify bringing his own food to a BBQ, but if you’re just an amateur, doing this will raise a few eyebrows (and potentially lose you a few friends).
When flexible dieting, you can indulge in things like this without ruining your diet. So long as everything fits into your daily macronutrient targets, you’ll stay on track.
One Final Point – Micronutrients Are Important!
One very pertinent criticism of IIFYM is the apparent lack of importance it assigns to micronutrients; vitamins, minerals, and so on.
Anybody who takes athletic performance, health, or aesthetics seriously knows that their micronutrient intake is just as important as their macronutrient intake.
So the fact that IIFYM only places importance on macros can seem like a major issue.
However, there is nothing in IIFYM that states “micronutrients don’t matter”. The main concern of IIFYM is monitoring macronutrient intake, but that doesn’t mean that nothing else matters.
There is no stipulation in IIFYM that you need to train to maximize fat loss and muscle retention.
There is no stipulation that you need to sleep more than 4 hours every night.
It doesn’t mention stress levels, hormone levels, or anything other than macronutrient intake, but we all know that these things are important.
As stated near the beginning of this article, most people who say that flexible dieting works assume that the person following it has a basic grasp of good nutrition.
When a personal trainer advocates IIFYM, they are assuming that the person they are talking to will not stop getting their recommended daily intake of vitamins and minerals, just as they assume they will continue to sleep, rest, and train properly.