By Eric Trexler, CSCS, CISSN

Former Director of Research and Education, INOV8 Elite Performance

When it comes to nutrition and dieting advice, there is a ton of information out there. Unfortunately much of it is nonsense, and with each new gimmick or trend in the world of nutrition, useful information becomes even more sparse and difficult to locate.

The following article aims to uncover the basic, essential elements necessary for a successful approach to dieting, and ultimately provide a practical guide to the “IIFYM” style of dieting (also known as “flexible dieting”).

What is Flexible Dieting/IIFYM?

Somewhere along the line of bodybuilding history, a short list of foods became labeled as “acceptable” for bodybuilders. While individual lists may vary slightly, we all know the main “bodybuilder foods”— chicken, tilapia, broccoli, brown rice, sweet potatoes, etc.

Flexible dieting can be simply described as a method of dieting that does not confine the dieter to such a short list of foods. They have more freedom to incorporate foods that fit their taste preferences, cooking skills, schedule, gastrointestinal tolerance, and so on.

In order to allow for a broad selection of food sources, the dieter sets daily macronutrient targets— these are target intakes for fat, carbohydrates, and protein. Such a dieter will commonly refer to their current macronutrient targets as their “macros.” As the legend goes, the acronym “IIFYM” (which stands for “If It Fits Your Macros”) began as a brief response on bodybuilding forums.

The acronym, often attributed to a friend of mine posting under the name “ErickStevens,” would be used in the follow scenario:

Poster #1: Can I eat (enter a food source that isn’t generally considered a “bodybuilder food”)?

Poster #2: IIFYM then EAT IT.

With the basic description out of the way, let’s discuss how to actually apply the concept of flexible dieting.

The “Hierarchy of Importance”

To borrow a term from Alan Aragon, there is a “Hierarchy of Importance” when it comes to dieting. Whether your goal is to lose fat or gain muscle, the Hierarchy will help focus your attention on what really matters. The most important aspects of the diet are at the top of the Hierarchy, beginning with total energy (Calorie) intake.

Calorie Intake

The most crucial aspect of a diet is total energy intake, as measured in Calories. When you break it down, dieting is pretty simple: When you consume more Calories than you burn, you gain weight. When you burn more than you consume, you lose weight. Although this view is admittedly oversimplified and fails to acknowledge the dynamic nature of human metabolism, energy intake is the single most critical factor of a diet aimed at manipulating body weight and composition. If you are the person who claims that they “can’t lose weight,” you are likely either underestimating your energy input or overestimating your output, both of which are quite common. The next critical component of your diet is figuring out how to split your Calories amongst the macronutrients.


Protein, fat, and carbohydrate are all considered “macronutrients”— nutrients that we consume in relatively large amounts, typically measured in grams. Whether or not you choose to consider alcohol a macronutrient, it yields a similar amount of energy when included in the diet. Macronutrient distribution refers to how your daily caloric intake is divided amongst the macronutrients.

For instance, a person eating 2800 Calories per day could eat 60 grams of fat, 160 grams of protein, and 405 grams of carbohydrate, but they could also eat 56 grams of fat, 120 grams of protein, and 454 grams of carbohydrate. The macronutrients each have distinct physiological roles that affect body composition, athletic performance, and various health parameters differently, so macronutrient distribution is an extremely important aspect of dieting.

Although attempting to set acceptable daily Calorie and macronutrient intakes requires a bit of footwork and frequent “guess and check” adjustments, the coaching staff at INOV8 Elite Performance is highly capable and more than willing to help you figure out your targets. Also, the following forum post by “Emma-Leigh” is a great resource to help walk you through the process.

Note: We now approach a fairly large gap in the Hierarchy. In terms of losing muscle or gaining fat, total energy intake and macronutrient distribution are far more important than any other aspects of the diet.

Meal Frequency and Meal Timing

Meal frequency and meal timing refer to how often you eat— how many meals per day, and the amount of time between meals. Dr. Layne Norton and his colleagues have demonstrated, through a series of studies utilizing rodent subjects, that it may be beneficial to divide protein intake evenly between multiple meals (Dr. Norton’s recommendation is 4-6 meals). A recent, relatively loosely-controlled study in elderly subjects suggests a similar outcome in humans. Until these results are replicated in tightly controlled studies with human (and preferably trained) subjects, one must practice caution when attempting to apply them to extremely specific recommendations. However, I think it is fair to recommend dividing protein intake evenly between multiple meals, spread throughout the day.

The classic notion that increased meal frequency boosts the metabolic rate has been flatly disproven by multiple studies. On the other end of the spectrum, studies investigating lower meal frequencies have not shown any beneficial effect on body composition. As the research currently stands, a simple recommendation would be to divide protein intake relatively evenly between roughly 3-6 meals, spaced somewhat evenly throughout the day. Ultimately, finding the right meal frequency for you depends on personal factors including appetite, preference, and daily schedule.

When discussing meal timing, nighttime carbohydrate intake is a common topic of conversation. Despite what you have heard in the past, there is nothing inherently “wrong” with eating carbs (or any other macronutrient) late at night. In fact, it has recently become somewhat popular to eat minimal carbohydrates throughout the morning and afternoon, saving the majority of the day’s carbohydrate intake for the final meals of the evening (see the followingarticle for more info). Although I remain skeptical of any physiological benefit from this strategy, it is certainly a viable option for carbohydrate distribution.

Another popular meal timing topic is what to eat before, during, and after a workout. A lot of conflicting evidence has been generated by studies investigating these time windows, mostly because a number of contextual factors can affect their relative importance. For example, in subjects who have fasted prior to their workout, timing of the post-workout feeding becomes far more important than it would normally be after a meal. Without writing out an extensive review of current research findings (which has been done masterfully in Alan Aragon’s research review and the following article), I will get straight to the point.


The pre-workout meal should contain a combination of protein and carbohydrate aimed at supporting energy levels and attenuating extensive muscle breakdown throughout the workout. The size and timing of this meal should be determined by a number of variables, including appetite, gastrointestinal tolerance, and the overall intensity and duration of the workout.

For example, imagine you have a particularly long, arduous workout planned. You might choose to have a larger pre-workout supply of carbohydrate to help fuel your training. The intense nature of said workout, combined with the size of the meal, may also require that the meal be ingested a bit longer before training to prevent digestion issues. Generally speaking, the protein dosage of this meal should be pretty similar to the post-workout meal (anywhere from 20-40 grams should be sufficient for most, depending on body size).

While it is important to fuel your workout, some may have issues keeping down a robust pre-workout meal. If this is an issue, try ingesting your meal a bit longer before training, consuming a liquid meal instead of solid food, and/or limiting the fat and fiber content of the meal.


The post-workout meal should contain plenty of protein aimed at facilitating muscle protein synthesis (recommendations generally range from roughly 20 to 40 grams, depending on body size). Given that pre-workout nutrition is sufficient and daily macronutrient intakes are appropriate, the specific timing of the post-workout meal does not appear to be crucial, contrary to popular belief. It is important to eat following a training bout, but it is not necessary to rush— slamming a liquid meal within ten minutes of your workout is unlikely to be any more effective than a home-cooked meal consumed an hour after the workout’s conclusion.

Another popular belief is that people must take in large quantities of fast-digesting carbohydrates immediately post-workout to spike insulin and kick-start glycogen replenishment. In reality, research demonstrates that modest amounts of protein alone can spike insulin to a level that maximizes its inhibitory effect on muscle protein breakdown. Further, rapid glycogen replenishment is only a pressing matter to an extremely small percentage of the training population (for example, a track athlete who has multiple lower-body training sessions or runs multiple glycogen-depleting events within a single day). Similarly to the pre-workout meal, including fat in the post-workout meal will not be detrimental, especially since gastrointestinal tolerance is not likely to be as big an issue after the workout.

Given this information, the post-workout meal becomes really simple: Eat enough protein, and fill in an appropriate amount of carbs and fats. An “appropriate amount” is one that fits your personal preference for that meal and fits within your total macronutrient intakes for the day. Ultimately, proper daily macronutrient intake is far more important than any magical combination of nutrients consumed within a precise time window.


For most trainees, proper pre-workout nutrition alleviates the need for intra-workout Calorie consumption. However, for trainees engaged in strenuous, glycogen-depleting activities lasting over an hour, a sports beverage containing carbohydrate alone, or a mix of carbohydrate and lesser amounts of protein/amino acids, may be advised. When choosing an intra-workout source of amino acids, gastrointestinal tolerance may be an important factor for some. While the digestion of intact proteins might be difficult during exercise, hydrolyzed proteins or mixtures of BCAAs/EAAs may be a more tolerable option.

The exact amount of intra-workout carbohydrate depends on a number of factors (the size of the athlete, the intensity of the exercise, the duration of exercise, etc.). General recommendations usually call for 30-60 grams of carbohydrate per hour, mixed in a 5-8% solution (5-8 grams of carbs per 100 mL of fluid). This concentration is considered ideal for absorption from the gastrointestinal tract, and most popular sports drinks fit within this range.

Food Selection

This is the section where most dieting articles offer one of two suggestions: Get used to boring food, or learn how to get really creative with chicken breast. Food selection has been addressed last because it is the least critical component of the diet. If you hit your Calorie and macronutrient targets for the day, you can lose weight eating virtually any food that fits. Pizza, ice cream, cake… You get the idea.

Some foods have high energy density, meaning they contain a lot of Calories per a given serving size. Conversely, some foods have high micronutrient density, meaning they contain high levels of vitamins and minerals per a given serving size. It is common to hear the term “clean” used to describe a food with relatively high micronutrient density and low energy density, though this definition is not universally agreed upon.

It is important to understand that 400 “clean” Calories will likely provide you with more vitamins and minerals, but they will not make you any leaner than 400 calories of “junk food.” So, in the short-term, a person who burns 3,000 Calories per day will experience the same weight loss from 2,600 Calories of “clean” food as from 2,600 Calories of “junk food.”

However, it is important to point out a few things. First: When following a “flexible” diet, the overwhelming majority of foods consumed should be high in micronutrient content.

Second, it is important to consider health and performance. Imagine Diet A is primarily composed of nutritious, micronutrient-dense foods and Diet B has the same macros but yields insufficient intakes of important micronutrients. Diet A is likely to yield better performance, recovery, and overall health outcomes in the long run, which could ultimately result in a superior physique, depending on exactly how deficient Diet B is.

Third, it is important to consider satiety or “fullness” when dieting. If a dieter is on low Calories toward the end of contest prep, they might choose “cleaner” foods with lower energy density and higher fiber content. This allows a higher volume of food intake for a given Calorie total and often helps to fight feelings of hunger. Conversely, if you are the type of person who struggles to eat enough food (especially when bulking), it may be helpful to incorporate some foods with high energy density. It is a lot easier to pack in 600+ grams of carbs when you replace some of your sweet potatoes or broccoli with modest amounts of pretzels or your favorite breakfast cereal.

Finally, one must consider protein quality. In terms of muscle protein synthesis, it is important to ensure sufficient intakes of essential amino acids (EAAs)— further, the branched-chain amino acids (BCAAs), especially leucine, are of elevated importance. “Complete” protein sources contain all essential amino acids in appropriate proportions and should be preferred sources of protein in the diet. Animal products (including eggs, dairy, meats, whey, etc.) tend to be excellent sources of EAAs, BCAAs, and leucine, making them ideal food choices. Vegans and vegetarians certainly can build tremendous physiques, but it may require extra attention to ensure sufficient intakes of key amino acids.

So, what should you eat?

The ideal approach is to fill most of your diet with a diverse selection of micronutrient-dense foods. Favor complete protein sources. Choose foods that fit your preferences regarding taste, preparation, gastrointestinal tolerance, and so on. Aim for the recommended intakes of fiber, vitamins, and minerals needed to support good health. After that goal is met, manage your remaining macros the same way you budget your money. If you’ve covered your expenses and have some income left over, feel free to treat yourself to something nice! And keep in mind that as long as you adhere to your daily Calorie and macronutrient goals, this is not a “cheat meal”— It will taste like one, but it will not set your diet back in any way.

Putting It All Together

Just remember to keep your approach simple! Adhere to the Hierarchy, and don’t sweat the small stuff. Set realistic goals, give yourself plenty of time to achieve them, and approach your diet as a marathon, not a sprint. The purpose of a diet is not to avoid all of your favorite foods until you break down— Budget your calories wisely, hit your daily macronutrient targets, and don’t let minor setbacks derail the entire effort.

To summarize this simple, practical approach to dieting:

  • Figure out appropriate Calorie and macronutrient intakes by consulting with a knowledgeable coach or readingthis forum post
  • Eat roughly 3-6 meals each day, spaced somewhat evenly throughout the day, with your daily protein allotment divided equally between them
  • Fitting your workout between any of those meals should satisfy your requirements for pre- and post-workout protein
  • Be sure to take in sufficient amounts of micronutrients and fiber
  • Distribute your carbs and fats in a way that fits your preferences and fuels your workouts
  • Be realistic, be patient, and don’t let minor setbacks turn into major setbacks!

Eric Trexler is not a doctor or registered dietitian. Eric holds no certification or licensure in the practice of nutrition or dietetics. The contents of this article should not be taken as medical advice. It is not intended to diagnose, treat, cure, or prevent any health problem – nor is it intended to replace the advice of a physician. Always consult your physician or qualified health professional on any matters regarding your health.