Flexible Dieting: The Ultimate Guide To IIFYM ‘If It Fits Your Macros’

In this guide, we will delve into the ancient debate of “clean” vs. “dirty” foods and what really makes sense physiologically speaking. After that, we will cover what IIFYM is, what some shortcomings of it are & how to correct them, what its pros are, and finally how to setup your IIFYM diet plan.


The Diverse Nature of Food

I’m generally disinterested in fixating arbitrary “percentages of importance” on the particular components of one’s fitness regimen–such as, “Your results are determined 90% by diet and 10% by exercise.” For now let’s just settle for nutrition being a major portion of the pie. But now that we have this large piece of pie on our plate we are faced with another conundrum—how much of this piece is “healthy/clean” and how much is “unhealthy/dirty?” This metaphor is already way out in left field, but I’m committed to it and don’t feel like starting over so bear with me. Let’s hypothetically say we have ourselves a big ol’ piece of pecan pie. Now you might be thinking, “Hey, pecans contain bounties of ‘healthy’ (read: clean), essential fatty acids so I’ll just eat that part of the pie.” But not so fast there you nut-lover. What about the gooey goodness that holds the pie together? All that butter and brown sugar that melts in your mouth each bite you take.

How about the graham cracker crust that lays the foundation for most any pecan pie? Are those portions of the pie inherently “dirty” and unhealthy for you?

The Relevance of the Term “Healthy”

Frankly, there is no short yes-or-no answer for the aforementioned questions because the term “healthy” is relevant to your own specific nutritional needs. People seem to haphazardly throw the word healthy around in certain pre-defined circumstances, but the reality is that what is healthy for one individual may or may not be healthy for another. In the Darwinian/biological sense, for something to be healthy, it serves to enhance the survivability/fitness of that organism.

Not to mention that the absurd amounts of performance-enhancing drugs many competitors use just compound the issue; the sad truth is that bodybuilding has increasingly become a sport/lifestyle that unbeknownst to the general public supports the ideology of sacrificing health to look a certain way. But I digress…

Why Extreme Diets Suck (in the long run)

More often than not, diets that present impractical stipulations and/or greatly restrict specific nutrients are not sustainable in the long run due to their rigid demands and favoring of imbalance. On the flipside, a more workable diet will likely have a much higher adherence rate. Something that seems to fly right over the head of so-called “fitness gurus” when they devise outlandish, extreme diets is that no matter how great something sounds on paper, it won’t work if it’s not practical and has some leeway; we’re humans, not machines. As alluded to earlier, bodybuilding and physique sports promote extreme lifestyles, and in fact that’s what has created the whole dichotomy of “clean” and “dirty” foods.

People, especially bodybuilders, look at certain foods and think “Rice, chicken and broccoli are all clean foods, so I will just stick rigidly to those and eliminate everything else.”


What the Heck Makes a Food “Clean” or “Dirty?”

Let’s take a step back and think about this logically…what makes, for example, a piece of boneless, skinless chicken breast “clean?” Is it the macronutrient profile, given that it’s pretty much just protein (or “brotein” I should say)? What about the micronutrient content? Maybe it’s “clean” because of the way it is was raised, free to roam the farm prior to being meeting its doom with the butcher? Like the preceding question about “clean” food, how do we categorize/define a food that is “dirty” or “junk?” I’m sure many readers immediately think of foods like pizza, burgers, and ice cream when they hear those terms. Why though? Is it because those foods tend to be processed, high in fat and/or sugar, and lacking micronutrient content?

Many questions have been brought up here, but fear not as answers are on the way.

Enter “If It Fits Your Macros” (IIFYM)

In recent years, IIFYM has become an increasingly popular dieting ideology in bodybuilding subculture. What’s never really made sense to me about this whole movement is that IIFYM isn’t really anything new or profound. In fact, IIFYM is the way pretty much everybody who has ever tracked their food intake has always eaten, with the exception that no foods are seen as off limits. Of course, in the bodybuilding and fitness world, the idea of no foods being off limits has sent many “clean” eaters into a frenzy, scolding IIFYM as being an inferior and illogical way of dieting.
This might be an eye-opener for some readers, especially if you have succumbed to the good ol’ chicken, rice and broccoli diet for the last decade, but the reality is that very few foods/ingredients are unanimously unhealthy and completely detrimental to your physique.

Barring specific food allergies (which lately everyone seems to have an undiagnosed case of Celiac disease) or an irrational fear of certain food additives (like monosodium glutamate), there is little basis to label a food as being universally “dirty” or unhealthy.


Toxicity is in the Dose

Now don’t get me wrong, there is plenty of research that goes into the potential deleterious effects of things like artificial ingredients and other food additives, but frankly if you’re not consuming these things day-in and day-out in gross quantities there is little to be afraid of. Some good examples that come to mind are partially hydrogenated oils and high-fructose corn syrup; both of these ingredients have received a terrible reputation, especially with their increasing use in our food supply and the concomitant rise in obesity rates.

Yes, trans-fatty that are produced from partial hydrogenation of oils have been shown to promote cardiac complications even in rather small quantities, but if you’re taking in say less than 1g of trans fat per day (which is not that hard to do unless you plan on inhaling Krispy Kreme doughnuts by the dozen) then the health ramifications will be negligible.

And as far as high-fructose corn syrup goes, it’s yet another case of limiting your intake, but frankly if you’re eating an otherwise healthy diet and controlling calorie intake, a bit of high-fructose corn syrup won’t make or break your physique or health.

Sadly, preaching moderation to a herd of extremist bodybuilders and fitness connoisseurs probably won’t bode well for the reception of this article, but this is actually a nice segue into the next section that looks at the shortcomings of the IIFYM mantra and how to correct them.

Logical Dieting 101: Eluding Deficiency and Excess

During the introduction of this article we discussed what it is that makes a diet/food healthy and how there is no one-size-fits-all algorithm out there that will spit out your precise nutritional needs. Naturally, this means you need to take time to learn your body’s specific metabolic needs, which will likely come through trial and error. The main thing to keep in mind however is that any healthy diet that keeps you performing at an optimal level should be eluding the extremes of taking in too much of a particular nutrient and/or being deficient in another nutrient, as well as meeting your daily calorie quota.

Whatever foods you choose to eat to satisfy this is simply a means to an end, and this is the gist of IIFYM.

However, one of the major pitfalls of IIFYM seems to be that some people use it as an excuse to disregard things like micronutrients, dietary fiber, the quality of protein sources, essential fatty acid intake and sugar consumption.

For example, a diet that contains an abundance of soy protein probably wouldn’t be nearly as effective for muscle building and fat loss purposes as one that contains higher quality, leucine-rich protein sources such as whey and eggs.

What IIFYM Really Is

For whatever reason, people read about IIFYM and think it’s a diet that gives them the freedom a bunch of Pop-Tarts and cookies to fill in the majority of their carb and fat needs. Unless you’re a genetic anomaly, excessive amounts of simple sugars, negligible amount of dietary fiber and a bunch of trans-fats probably won’t fit your macronutrient needs, especially if you’re trying to stay in good shape and be healthy. Furthermore, it’s not nearly as catchy but IIFYM should be renamed “IIFYM/µ.” Back to the preceding Pop-Tart example, good luck fulfilling your micronutrient needs eating Krispy Kremes all day with a few protein shakes scattered in there for the “brotein,” bro.

In all likelihood, if you’re trying to meet even halfway decent micronutrient and macronutrient intakes you will find yourself eating lean animal/animal-derived proteins, dairy, nuts/seeds, whole-grain carbohydrates, vegetables and fruits. I refuse to refer to these as “clean” foods though because that term is nonsensical; these are more properly foods that should be noted as “nutrient-dense” (this is bound to evoke semantic arguments but that’s a chance I’m willing to take).


Finding the Balance

Does this mean your diet has to be entirely comprised of the aforementioned nutrient-dense foods? Certainly not, and this is actually the upside of IIFYM in that it promotes balance and elasticity in one’s diet. Someone who wishes to incorporate some foods that are more nutrient-devoid/empty calorie can do that assuming they still reach their overall needs at the end of the day (and assuming they are balancing their macronutrient proportions at each feeding). It may take some time to wrap your head around this concept, but you’re only fooling yourself if you truly believe that a slice of pizza or grabbing some ice cream with your significant other is going to sabotage all your effort in the gym.

In fact, the irony is that many people who adhere rigidly to the idea of “clean” eating will simply give in after a short period of time and go on absolute binge-a-thons (colloquially called “cheat” days). Make no mistake, those binge episodes can and will wreak havoc on your body composition quickly.

A Typical “Clean” Diet Vs. IIFYM Meal Plan

Pick up any mainstream bodybuilding magazine and you’ll come across the same humdrum rubble that now defines pretty much every meathead’s diet.

Let’s take a look at an example of such a “clean” diet:

Typical “Clean” Diet

  • Meal 1: 6 egg whites, 80g dry oats, 1 oz almonds
  • Meal 2: (Pre-Workout) 1 scoop whey protein mixed with 40g dry oats, 1 tbsp Flaxseed oil
  • Meal 3: (Post workout) 2 scoops whey protein mixed with 50g simple-carb solution (i.e. waxy maize or pure dextrose)
  • Meal 4: 6 oz grilled chicken breast, 1 cup cooked brown rice, 2 cups steamed broccoli
  • Meal 5: 1 scoop whey protein mixed with 40g dry oats, 1 tbsp Flaxseed oil
  • Meal 6: 1 scoop casein protein, 1 oz mixed nuts, 2 cups steamed asparagus

Total Macronutrient Breakdown: 235g protein/215g carbs/80g fat
Total Calories: About 2,520

What a monotonous, bland diet. In fact, this type of dieting often leads to the loss of emotional pleasure that should normally come from eating. It’s sad that most people would see this diet and commend the individual on how “healthy” they eat when the reality is this diet is far from that.

Let’s take a look at an example of an IIFYM meal plan that breaks down to the exact same macros as the above diet:

Example IIFYM Meal Plan

  • Meal 1: 2 cup (~454g) nonfat greek yogurt mixed with ½ cup blueberries and 1 cup of Cheerios, 3-egg omelet with veggies and salsa
  • Meal 2: (Lunch at Chick-fil-a) 1 chargrilled chicken sandwich, 8-count order of chicken nuggets, 1 small fruit bowl, 1 medium diet soda
  • Meal 3: (Post-workout) 1 cup low-fat cottage cheese mixed with 1 scoop whey protein and 1 oz mixed nuts, 2 low-fat vanilla ice cream sandwiches
  • Meal 4: 1 cup cooked spaghetti noodles covered with half cup marinara sauce and 12 oz of 93% lean ground beef

Total Macronutrient Breakdown: 235g protein/215g carbs/80g fat
Total Calories: About 2,520

Now, tell me, which of the above two meal plans would you genuinely like to eat? I’d surmise that 99% of readers are going to choose the IIFYM plan over the aforementioned usual meathead diet.

Notice the flexibility in the IIFYM plan, allowing the individual to eat out and enjoy little indulgences here and there throughout the day.

Setting Up Your Own IIFYM Diet

A pragmatic way of calculating your energy/macronutrient needs is to start by using a BMR calculator and the Harris-Benedict equation to factor your daily activity levels (see link below). For most active weight trainees, eating around 1g of protein per pound of lean body weight is recommended. Once protein needs are set, you move onto carbohydrate demands (which will be largely dependent on your individual insulin sensitivity).

Then finally, once protein and carbohydrate demands are set, you “fill in” the rest of your caloric needs with fats.


Here’s an example of how this would work for someone with 175lbs of lean body mass on a 2750 calorie diet:

  • Determine Calorie Needs: BMR Calorie Calculator
  • Set protein intake at 1g/lb of lean body mass: 175g protein per day
  • This individual is highly insulin-sensitive so we’ll set his carbohydrate intake at 2g/lb of lean body mass: 350g carbohydrate per day (and roughly 10-15% of these should be fiber)
  • Since carbohydrates and proteins contain 4 calories per gram, then we have (175+350) x 4: 2100 calories from proteins and carbohydrates
  • Therefore, this individual’s fat intake will come from the leftover calories to reach 2750: 2750 – 2100 = 650 calories/9 calories per g of fat = ~72g of fat per day (and around 20-25% of these should be saturated fats)

The general rule of thumb if your goal is to lose fat is to aim for an energetic deficit of ~500 calories per day (most of which should come from reduced carb intake).

If you want to add mass, aim for an energetic surplus of 300-500 calories per day. Please note that these are generalizations, and you will need to experiment and find what suits your body best.


Macronutrient Balance: Do’s and Don’ts

A final point to touch on about IIFYM is that it doesn’t address macronutrient balance throughout each meal. Granted, most health and fitness enthusiasts know that they should be eating a nominal amount of complete protein sources (such as most animal proteins) with each feeding to provide a sufficient elevation in muscle protein synthesis. Yes, calories are ultimately what determine whether we gain or lose weight, but there will certainly be different physiological effects from a diet that greatly skews macronutrient intake.

To illustrate this example, here are two different isocaloric diet plans that have identical macronutrient intakes (~2500 calories consisting of 150g protein, 300g carbohydrate, and 75-80g fat) but have highly differing macronutrient balance throughout the day:

Diet Layout 1

(Balanced intake with higher carbs around the workout timeframe)

  • Meal 1—600 cals/40g pro/50g carb/15g fat
  • Meal 2—450 cals/30g pro/50g carb/15g fat
  • Meal 3—390 cals/25g pro/80g carb/10g fat (Pre-training Meal)
  • Meal 4—575 cals/30g pro/80g carb/15g fat (Post-training Meal)
  • Meal 5—505 cals/30g pro/40g carb/25g fat

Diet Layout 2

(Imbalanced intake)

  • Meal 1—665 cals/5g pro/150g carb/5g fat
  • Meal 2—465 cals/5g pro/100g carb/5g fat
  • Meal 3—660 cals/5g pro/25g carb/60g fat (Pre-training Meal)
  • Meal 4—225 cals/25g pro/20g carb/5g fat (Post-training Meal)
  • Meal 5—480 cals/110g pro/5g carb/5g fat

The calorie balances at each meal are actually similar between these two diets, but you can clearly see the skewed (to a fault) distribution of macronutrients in Diet Layout 2. The second diet loads up on carbs while neglecting protein and fats in the first three meals. It also doesn’t make much sense to stuff yourself full of carbs early on and then load up on fats before training. Also, the last meal of the day simply has an excessive amount of protein in it. Now I know most people who have even rudimentary understanding of performance nutrition would never balance their macronutrient intake as proposed in Diet Layout 2.

This diet comparison is simply meant to illustrate the point that IIFYM can be misconstrued to mean that macronutrient distribution throughout the day doesn’t matter when trying to improve body composition…it may not play a major role, but it still plays a role nonetheless.

Extreme Dieting Doesn’t Make you Hardcore

One thing that has always piqued my curiosity about many bodybuilders’ train of thought is the supposition that a monotonous, bland, super-duper-ultra “clean” diet is somehow better for physique and performance purposes than a diet that has variety and actually taste decent. This whole idea of being “hardcore” because all you eat is plain chicken breast, brown rice and asparagus needs to vanish. Newsflash for you, eating plain, tasteless, dry-as-the-Arabian desert chicken breast doesn’t make you better, healthier or more hardcore than the next guy…it makes you a lame-brained meathead that doesn’t know his way around the kitchen (which is so ironic, given that most bodybuilders spend 50% of their day in there).

If you’re yearning for a sense of accomplishment for being hardcore, than figure out how to implement foods you genuinely want to eat into your diet. Quite frankly, that’s the essence of someone who has control over their life and has found a proper balance with their diet.

Being Creative and Mindful with Your Food Choices

There are a googol of ways to eat a healthful, nutrient-dense diet that propels your physique and performance while making it taste good. Don’t succumb to the fatuous idea that you have to sacrifice taste and psychological enjoyment of the foods you eat to achieve the body of your dreams. What IIFYM teaches us is that you really can have your cake and eat it too if you exercise some creativity and portion control into your daily routine. If you want to enjoy a couple scoops of Ben and Jerry’s with your kids or take your significant other out for dinner, then plan ahead and work that into your diet.

If you choose to believe that forgoing those things makes you more hardcore or prone to success as a bodybuilder, then I guess you have really been brainwashed by mainstream media and bogus fitness magazines over the years. At that point there really is no other term to describe your thinking than utter meat-headedness.

Psychology of Eating: What IIFYM Teaches Us

One of the primary goals of this guide was to provide impartial insight into both the pros and cons of IIFYM. That being said, I would be remiss to not touch on a final, crucial point that I believe IIFYM can teach many bodybuilders and fitness enthusiasts–that your diet has a psychological aspect to it. Eating, at its very core, is a biological necessity (and privilege) that sustains us both mentally and physically; it’s not a chore that you should hold in disdain and think of as a sacrifice.

If there’s something we can all learn from IIFYM it’s that a healthy diet reinforces psychological connections with food while working towards your health, physique and performance goals.


  1. Smith, C. F., Williamson, D. A., Bray, G. A., & Ryan, D. H. (1999). Flexible vs. Rigid dieting strategies: relationship with adverse behavioral outcomes.Appetite, 32(3), 295-305.
  2. Mela, D. J. (2001). Determinants of food choice: relationships with obesity and weight control. Obesity research, 9(S11), 249S-255S.
  3. Teegala SM, et al. Consumption and health effects of trans fatty acids: A review. Journal of AOAC International. 2009;92:1250.
  4. Moeller S, et al. The effects of high fructose syrup. Journal of the American College of Nutrition. 2009;28:619.
  5. Tang, J. E., Moore, D. R., Kujbida, G. W., Tarnopolsky, M. A., & Phillips, S. M. (2009). Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. Journal of Applied Physiology, 107(3), 987-992.
  6. Baer, D. J., Stote, K. S., Paul, D. R., Harris, G. K., Rumpler, W. V., & Clevidence, B. A. (2011). Whey protein but not soy protein supplementation alters body weight and composition in free-living overweight and obese adults.The Journal of nutrition, 141(8), 1489-1494.
  7. Tipton, K. D., & Wolfe, R. R. (2004). Protein and amino acids for athletes.Journal of sports sciences, 22(1), 65-79.
  8. Phillips, S. M., & Van Loon, L. J. (2011). Dietary protein for athletes: from requirements to optimum adaptation. Journal of sports sciences, 29(sup1), S29-S38.
  9. Norton LE, Wilson GJ, Layman DK, Moulton CJ, Garlick PJ. (2012) Leucine content of dietary proteins is a determinant of postprandial skeletal muscle protein synthesis in adult rats. Nutr Metab (Lond). 2012 Jul 20;9(1):67. doi: 10.1186/1743-7075-9-67. PubMed PMID: 22818257; PubMed Central PMCID: PMC3488566